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493 lines
20 KiB
Rust
493 lines
20 KiB
Rust
//! Set and unset common attributes on LLVM values.
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use rustc_codegen_ssa::traits::*;
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use rustc_data_structures::small_str::SmallStr;
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use rustc_hir::def_id::DefId;
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use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
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use rustc_middle::ty::{self, TyCtxt};
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use rustc_session::config::OptLevel;
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use rustc_span::symbol::sym;
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use rustc_target::spec::abi::Abi;
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use rustc_target::spec::{FramePointer, SanitizerSet, StackProbeType, StackProtector};
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use smallvec::SmallVec;
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use crate::attributes;
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use crate::errors::{MissingFeatures, SanitizerMemtagRequiresMte, TargetFeatureDisableOrEnable};
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use crate::llvm::AttributePlace::Function;
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use crate::llvm::{self, AllocKindFlags, Attribute, AttributeKind, AttributePlace, MemoryEffects};
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use crate::llvm_util;
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pub use rustc_attr::{InlineAttr, InstructionSetAttr, OptimizeAttr};
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use crate::context::CodegenCx;
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use crate::value::Value;
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pub fn apply_to_llfn(llfn: &Value, idx: AttributePlace, attrs: &[&Attribute]) {
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if !attrs.is_empty() {
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llvm::AddFunctionAttributes(llfn, idx, attrs);
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}
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}
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pub fn apply_to_callsite(callsite: &Value, idx: AttributePlace, attrs: &[&Attribute]) {
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if !attrs.is_empty() {
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llvm::AddCallSiteAttributes(callsite, idx, attrs);
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}
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}
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/// Get LLVM attribute for the provided inline heuristic.
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#[inline]
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fn inline_attr<'ll>(cx: &CodegenCx<'ll, '_>, inline: InlineAttr) -> Option<&'ll Attribute> {
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if !cx.tcx.sess.opts.unstable_opts.inline_llvm {
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// disable LLVM inlining
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return Some(AttributeKind::NoInline.create_attr(cx.llcx));
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}
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match inline {
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InlineAttr::Hint => Some(AttributeKind::InlineHint.create_attr(cx.llcx)),
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InlineAttr::Always => Some(AttributeKind::AlwaysInline.create_attr(cx.llcx)),
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InlineAttr::Never => {
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if cx.sess().target.arch != "amdgpu" {
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Some(AttributeKind::NoInline.create_attr(cx.llcx))
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} else {
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None
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}
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}
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InlineAttr::None => None,
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}
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}
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/// Get LLVM sanitize attributes.
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#[inline]
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pub fn sanitize_attrs<'ll>(
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cx: &CodegenCx<'ll, '_>,
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no_sanitize: SanitizerSet,
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) -> SmallVec<[&'ll Attribute; 4]> {
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let mut attrs = SmallVec::new();
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let enabled = cx.tcx.sess.opts.unstable_opts.sanitizer - no_sanitize;
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if enabled.contains(SanitizerSet::ADDRESS) || enabled.contains(SanitizerSet::KERNELADDRESS) {
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attrs.push(llvm::AttributeKind::SanitizeAddress.create_attr(cx.llcx));
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}
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if enabled.contains(SanitizerSet::MEMORY) {
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attrs.push(llvm::AttributeKind::SanitizeMemory.create_attr(cx.llcx));
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}
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if enabled.contains(SanitizerSet::THREAD) {
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attrs.push(llvm::AttributeKind::SanitizeThread.create_attr(cx.llcx));
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}
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if enabled.contains(SanitizerSet::HWADDRESS) {
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attrs.push(llvm::AttributeKind::SanitizeHWAddress.create_attr(cx.llcx));
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}
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if enabled.contains(SanitizerSet::SHADOWCALLSTACK) {
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attrs.push(llvm::AttributeKind::ShadowCallStack.create_attr(cx.llcx));
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}
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if enabled.contains(SanitizerSet::MEMTAG) {
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// Check to make sure the mte target feature is actually enabled.
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let features = cx.tcx.global_backend_features(());
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let mte_feature =
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features.iter().map(|s| &s[..]).rfind(|n| ["+mte", "-mte"].contains(&&n[..]));
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if let None | Some("-mte") = mte_feature {
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cx.tcx.sess.emit_err(SanitizerMemtagRequiresMte);
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}
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attrs.push(llvm::AttributeKind::SanitizeMemTag.create_attr(cx.llcx));
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}
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attrs
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}
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/// Tell LLVM to emit or not emit the information necessary to unwind the stack for the function.
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#[inline]
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pub fn uwtable_attr(llcx: &llvm::Context) -> &Attribute {
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// NOTE: We should determine if we even need async unwind tables, as they
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// take have more overhead and if we can use sync unwind tables we
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// probably should.
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llvm::CreateUWTableAttr(llcx, true)
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}
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pub fn frame_pointer_type_attr<'ll>(cx: &CodegenCx<'ll, '_>) -> Option<&'ll Attribute> {
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let mut fp = cx.sess().target.frame_pointer;
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let opts = &cx.sess().opts;
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// "mcount" function relies on stack pointer.
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// See <https://sourceware.org/binutils/docs/gprof/Implementation.html>.
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if opts.unstable_opts.instrument_mcount || matches!(opts.cg.force_frame_pointers, Some(true)) {
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fp = FramePointer::Always;
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}
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let attr_value = match fp {
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FramePointer::Always => "all",
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FramePointer::NonLeaf => "non-leaf",
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FramePointer::MayOmit => return None,
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};
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Some(llvm::CreateAttrStringValue(cx.llcx, "frame-pointer", attr_value))
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}
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/// Tell LLVM what instrument function to insert.
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#[inline]
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fn instrument_function_attr<'ll>(cx: &CodegenCx<'ll, '_>) -> SmallVec<[&'ll Attribute; 4]> {
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let mut attrs = SmallVec::new();
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if cx.sess().opts.unstable_opts.instrument_mcount {
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// Similar to `clang -pg` behavior. Handled by the
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// `post-inline-ee-instrument` LLVM pass.
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// The function name varies on platforms.
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// See test/CodeGen/mcount.c in clang.
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let mcount_name = cx.sess().target.mcount.as_ref();
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attrs.push(llvm::CreateAttrStringValue(
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cx.llcx,
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"instrument-function-entry-inlined",
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&mcount_name,
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));
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}
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if let Some(options) = &cx.sess().opts.unstable_opts.instrument_xray {
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// XRay instrumentation is similar to __cyg_profile_func_{enter,exit}.
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// Function prologue and epilogue are instrumented with NOP sleds,
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// a runtime library later replaces them with detours into tracing code.
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if options.always {
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attrs.push(llvm::CreateAttrStringValue(cx.llcx, "function-instrument", "xray-always"));
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}
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if options.never {
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attrs.push(llvm::CreateAttrStringValue(cx.llcx, "function-instrument", "xray-never"));
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}
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if options.ignore_loops {
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attrs.push(llvm::CreateAttrString(cx.llcx, "xray-ignore-loops"));
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}
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// LLVM will not choose the default for us, but rather requires specific
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// threshold in absence of "xray-always". Use the same default as Clang.
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let threshold = options.instruction_threshold.unwrap_or(200);
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attrs.push(llvm::CreateAttrStringValue(
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cx.llcx,
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"xray-instruction-threshold",
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&threshold.to_string(),
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));
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if options.skip_entry {
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attrs.push(llvm::CreateAttrString(cx.llcx, "xray-skip-entry"));
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}
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if options.skip_exit {
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attrs.push(llvm::CreateAttrString(cx.llcx, "xray-skip-exit"));
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}
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}
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attrs
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}
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fn nojumptables_attr<'ll>(cx: &CodegenCx<'ll, '_>) -> Option<&'ll Attribute> {
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if !cx.sess().opts.unstable_opts.no_jump_tables {
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return None;
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}
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Some(llvm::CreateAttrStringValue(cx.llcx, "no-jump-tables", "true"))
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}
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fn probestack_attr<'ll>(cx: &CodegenCx<'ll, '_>) -> Option<&'ll Attribute> {
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// Currently stack probes seem somewhat incompatible with the address
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// sanitizer and thread sanitizer. With asan we're already protected from
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// stack overflow anyway so we don't really need stack probes regardless.
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if cx
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.sess()
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.opts
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.unstable_opts
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.sanitizer
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.intersects(SanitizerSet::ADDRESS | SanitizerSet::THREAD)
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{
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return None;
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}
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// probestack doesn't play nice either with `-C profile-generate`.
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if cx.sess().opts.cg.profile_generate.enabled() {
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return None;
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}
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// probestack doesn't play nice either with gcov profiling.
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if cx.sess().opts.unstable_opts.profile {
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return None;
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}
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let attr_value = match cx.sess().target.stack_probes {
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StackProbeType::None => return None,
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// Request LLVM to generate the probes inline. If the given LLVM version does not support
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// this, no probe is generated at all (even if the attribute is specified).
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StackProbeType::Inline => "inline-asm",
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// Flag our internal `__rust_probestack` function as the stack probe symbol.
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// This is defined in the `compiler-builtins` crate for each architecture.
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StackProbeType::Call => "__rust_probestack",
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// Pick from the two above based on the LLVM version.
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StackProbeType::InlineOrCall { min_llvm_version_for_inline } => {
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if llvm_util::get_version() < min_llvm_version_for_inline {
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"__rust_probestack"
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} else {
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"inline-asm"
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}
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}
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};
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Some(llvm::CreateAttrStringValue(cx.llcx, "probe-stack", attr_value))
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}
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fn stackprotector_attr<'ll>(cx: &CodegenCx<'ll, '_>) -> Option<&'ll Attribute> {
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let sspattr = match cx.sess().stack_protector() {
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StackProtector::None => return None,
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StackProtector::All => AttributeKind::StackProtectReq,
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StackProtector::Strong => AttributeKind::StackProtectStrong,
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StackProtector::Basic => AttributeKind::StackProtect,
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};
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Some(sspattr.create_attr(cx.llcx))
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}
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pub fn target_cpu_attr<'ll>(cx: &CodegenCx<'ll, '_>) -> &'ll Attribute {
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let target_cpu = llvm_util::target_cpu(cx.tcx.sess);
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llvm::CreateAttrStringValue(cx.llcx, "target-cpu", target_cpu)
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}
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pub fn tune_cpu_attr<'ll>(cx: &CodegenCx<'ll, '_>) -> Option<&'ll Attribute> {
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llvm_util::tune_cpu(cx.tcx.sess)
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.map(|tune_cpu| llvm::CreateAttrStringValue(cx.llcx, "tune-cpu", tune_cpu))
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}
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/// Get the `NonLazyBind` LLVM attribute,
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/// if the codegen options allow skipping the PLT.
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pub fn non_lazy_bind_attr<'ll>(cx: &CodegenCx<'ll, '_>) -> Option<&'ll Attribute> {
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// Don't generate calls through PLT if it's not necessary
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if !cx.sess().needs_plt() {
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Some(AttributeKind::NonLazyBind.create_attr(cx.llcx))
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} else {
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None
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}
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}
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/// Get the default optimizations attrs for a function.
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#[inline]
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pub(crate) fn default_optimisation_attrs<'ll>(
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cx: &CodegenCx<'ll, '_>,
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) -> SmallVec<[&'ll Attribute; 2]> {
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let mut attrs = SmallVec::new();
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match cx.sess().opts.optimize {
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OptLevel::Size => {
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attrs.push(llvm::AttributeKind::OptimizeForSize.create_attr(cx.llcx));
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}
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OptLevel::SizeMin => {
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attrs.push(llvm::AttributeKind::MinSize.create_attr(cx.llcx));
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attrs.push(llvm::AttributeKind::OptimizeForSize.create_attr(cx.llcx));
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}
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_ => {}
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}
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attrs
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}
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fn create_alloc_family_attr(llcx: &llvm::Context) -> &llvm::Attribute {
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llvm::CreateAttrStringValue(llcx, "alloc-family", "__rust_alloc")
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}
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/// Composite function which sets LLVM attributes for function depending on its AST (`#[attribute]`)
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/// attributes.
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pub fn from_fn_attrs<'ll, 'tcx>(
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cx: &CodegenCx<'ll, 'tcx>,
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llfn: &'ll Value,
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instance: ty::Instance<'tcx>,
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) {
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let codegen_fn_attrs = cx.tcx.codegen_fn_attrs(instance.def_id());
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let mut to_add = SmallVec::<[_; 16]>::new();
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match codegen_fn_attrs.optimize {
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OptimizeAttr::None => {
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to_add.extend(default_optimisation_attrs(cx));
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}
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OptimizeAttr::Size => {
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to_add.push(llvm::AttributeKind::MinSize.create_attr(cx.llcx));
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to_add.push(llvm::AttributeKind::OptimizeForSize.create_attr(cx.llcx));
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}
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OptimizeAttr::Speed => {}
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}
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let inline =
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if codegen_fn_attrs.inline == InlineAttr::None && instance.def.requires_inline(cx.tcx) {
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InlineAttr::Hint
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} else {
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codegen_fn_attrs.inline
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};
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to_add.extend(inline_attr(cx, inline));
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// The `uwtable` attribute according to LLVM is:
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//
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// This attribute indicates that the ABI being targeted requires that an
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// unwind table entry be produced for this function even if we can show
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// that no exceptions passes by it. This is normally the case for the
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// ELF x86-64 abi, but it can be disabled for some compilation units.
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//
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// Typically when we're compiling with `-C panic=abort` (which implies this
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// `no_landing_pads` check) we don't need `uwtable` because we can't
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// generate any exceptions! On Windows, however, exceptions include other
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// events such as illegal instructions, segfaults, etc. This means that on
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// Windows we end up still needing the `uwtable` attribute even if the `-C
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// panic=abort` flag is passed.
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//
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// You can also find more info on why Windows always requires uwtables here:
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// https://bugzilla.mozilla.org/show_bug.cgi?id=1302078
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if cx.sess().must_emit_unwind_tables() {
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to_add.push(uwtable_attr(cx.llcx));
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}
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if cx.sess().opts.unstable_opts.profile_sample_use.is_some() {
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to_add.push(llvm::CreateAttrString(cx.llcx, "use-sample-profile"));
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}
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// FIXME: none of these three functions interact with source level attributes.
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to_add.extend(frame_pointer_type_attr(cx));
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to_add.extend(instrument_function_attr(cx));
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to_add.extend(nojumptables_attr(cx));
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to_add.extend(probestack_attr(cx));
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to_add.extend(stackprotector_attr(cx));
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if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::COLD) {
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to_add.push(AttributeKind::Cold.create_attr(cx.llcx));
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}
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if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::FFI_RETURNS_TWICE) {
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to_add.push(AttributeKind::ReturnsTwice.create_attr(cx.llcx));
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}
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if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::FFI_PURE) {
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to_add.push(MemoryEffects::ReadOnly.create_attr(cx.llcx));
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}
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if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::FFI_CONST) {
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to_add.push(MemoryEffects::None.create_attr(cx.llcx));
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}
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if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::NAKED) {
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to_add.push(AttributeKind::Naked.create_attr(cx.llcx));
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// HACK(jubilee): "indirect branch tracking" works by attaching prologues to functions.
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// And it is a module-level attribute, so the alternative is pulling naked functions into new LLVM modules.
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// Otherwise LLVM's "naked" functions come with endbr prefixes per https://github.com/rust-lang/rust/issues/98768
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to_add.push(AttributeKind::NoCfCheck.create_attr(cx.llcx));
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// Need this for AArch64.
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to_add.push(llvm::CreateAttrStringValue(cx.llcx, "branch-target-enforcement", "false"));
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}
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if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::ALLOCATOR)
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|| codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::ALLOCATOR_ZEROED)
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{
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if llvm_util::get_version() >= (15, 0, 0) {
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to_add.push(create_alloc_family_attr(cx.llcx));
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// apply to argument place instead of function
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let alloc_align = AttributeKind::AllocAlign.create_attr(cx.llcx);
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attributes::apply_to_llfn(llfn, AttributePlace::Argument(1), &[alloc_align]);
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to_add.push(llvm::CreateAllocSizeAttr(cx.llcx, 0));
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let mut flags = AllocKindFlags::Alloc | AllocKindFlags::Aligned;
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if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::ALLOCATOR) {
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flags |= AllocKindFlags::Uninitialized;
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} else {
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flags |= AllocKindFlags::Zeroed;
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}
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to_add.push(llvm::CreateAllocKindAttr(cx.llcx, flags));
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}
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// apply to return place instead of function (unlike all other attributes applied in this function)
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let no_alias = AttributeKind::NoAlias.create_attr(cx.llcx);
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attributes::apply_to_llfn(llfn, AttributePlace::ReturnValue, &[no_alias]);
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}
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if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::REALLOCATOR) {
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if llvm_util::get_version() >= (15, 0, 0) {
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to_add.push(create_alloc_family_attr(cx.llcx));
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to_add.push(llvm::CreateAllocKindAttr(
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cx.llcx,
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AllocKindFlags::Realloc | AllocKindFlags::Aligned,
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));
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// applies to argument place instead of function place
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let allocated_pointer = AttributeKind::AllocatedPointer.create_attr(cx.llcx);
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attributes::apply_to_llfn(llfn, AttributePlace::Argument(0), &[allocated_pointer]);
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// apply to argument place instead of function
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let alloc_align = AttributeKind::AllocAlign.create_attr(cx.llcx);
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attributes::apply_to_llfn(llfn, AttributePlace::Argument(2), &[alloc_align]);
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to_add.push(llvm::CreateAllocSizeAttr(cx.llcx, 3));
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}
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let no_alias = AttributeKind::NoAlias.create_attr(cx.llcx);
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attributes::apply_to_llfn(llfn, AttributePlace::ReturnValue, &[no_alias]);
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}
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if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::DEALLOCATOR) {
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if llvm_util::get_version() >= (15, 0, 0) {
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to_add.push(create_alloc_family_attr(cx.llcx));
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to_add.push(llvm::CreateAllocKindAttr(cx.llcx, AllocKindFlags::Free));
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// applies to argument place instead of function place
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let allocated_pointer = AttributeKind::AllocatedPointer.create_attr(cx.llcx);
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attributes::apply_to_llfn(llfn, AttributePlace::Argument(0), &[allocated_pointer]);
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}
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}
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if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::CMSE_NONSECURE_ENTRY) {
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to_add.push(llvm::CreateAttrString(cx.llcx, "cmse_nonsecure_entry"));
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}
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if let Some(align) = codegen_fn_attrs.alignment {
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llvm::set_alignment(llfn, align as usize);
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}
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to_add.extend(sanitize_attrs(cx, codegen_fn_attrs.no_sanitize));
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// Always annotate functions with the target-cpu they are compiled for.
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// Without this, ThinLTO won't inline Rust functions into Clang generated
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// functions (because Clang annotates functions this way too).
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to_add.push(target_cpu_attr(cx));
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// tune-cpu is only conveyed through the attribute for our purpose.
|
|
// The target doesn't care; the subtarget reads our attribute.
|
|
to_add.extend(tune_cpu_attr(cx));
|
|
|
|
let function_features =
|
|
codegen_fn_attrs.target_features.iter().map(|f| f.as_str()).collect::<Vec<&str>>();
|
|
|
|
if let Some(f) = llvm_util::check_tied_features(
|
|
cx.tcx.sess,
|
|
&function_features.iter().map(|f| (*f, true)).collect(),
|
|
) {
|
|
let span = cx
|
|
.tcx
|
|
.get_attrs(instance.def_id(), sym::target_feature)
|
|
.next()
|
|
.map_or_else(|| cx.tcx.def_span(instance.def_id()), |a| a.span);
|
|
cx.tcx
|
|
.sess
|
|
.create_err(TargetFeatureDisableOrEnable {
|
|
features: f,
|
|
span: Some(span),
|
|
missing_features: Some(MissingFeatures),
|
|
})
|
|
.emit();
|
|
return;
|
|
}
|
|
|
|
let mut function_features = function_features
|
|
.iter()
|
|
.flat_map(|feat| {
|
|
llvm_util::to_llvm_features(cx.tcx.sess, feat).into_iter().map(|f| format!("+{}", f))
|
|
})
|
|
.chain(codegen_fn_attrs.instruction_set.iter().map(|x| match x {
|
|
InstructionSetAttr::ArmA32 => "-thumb-mode".to_string(),
|
|
InstructionSetAttr::ArmT32 => "+thumb-mode".to_string(),
|
|
}))
|
|
.collect::<Vec<String>>();
|
|
|
|
if cx.tcx.sess.target.is_like_wasm {
|
|
// If this function is an import from the environment but the wasm
|
|
// import has a specific module/name, apply them here.
|
|
if let Some(module) = wasm_import_module(cx.tcx, instance.def_id()) {
|
|
to_add.push(llvm::CreateAttrStringValue(cx.llcx, "wasm-import-module", &module));
|
|
|
|
let name =
|
|
codegen_fn_attrs.link_name.unwrap_or_else(|| cx.tcx.item_name(instance.def_id()));
|
|
let name = name.as_str();
|
|
to_add.push(llvm::CreateAttrStringValue(cx.llcx, "wasm-import-name", name));
|
|
}
|
|
|
|
// The `"wasm"` abi on wasm targets automatically enables the
|
|
// `+multivalue` feature because the purpose of the wasm abi is to match
|
|
// the WebAssembly specification, which has this feature. This won't be
|
|
// needed when LLVM enables this `multivalue` feature by default.
|
|
if !cx.tcx.is_closure(instance.def_id()) {
|
|
let abi = cx.tcx.fn_sig(instance.def_id()).skip_binder().abi();
|
|
if abi == Abi::Wasm {
|
|
function_features.push("+multivalue".to_string());
|
|
}
|
|
}
|
|
}
|
|
|
|
let global_features = cx.tcx.global_backend_features(()).iter().map(|s| s.as_str());
|
|
let function_features = function_features.iter().map(|s| s.as_str());
|
|
let target_features =
|
|
global_features.chain(function_features).intersperse(",").collect::<SmallStr<1024>>();
|
|
if !target_features.is_empty() {
|
|
to_add.push(llvm::CreateAttrStringValue(cx.llcx, "target-features", &target_features));
|
|
}
|
|
|
|
attributes::apply_to_llfn(llfn, Function, &to_add);
|
|
}
|
|
|
|
fn wasm_import_module(tcx: TyCtxt<'_>, id: DefId) -> Option<&String> {
|
|
tcx.wasm_import_module_map(id.krate).get(&id)
|
|
}
|