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	Currently we whether or not to build and test `f16` and `f128` support
mostly based on the target triple. This isn't always accurate, however,
since support also varies by backend and the backend version.
Since recently, `rustc` is aware of this with the unstable config option
`target_has_reliable_{f16,f128}`, which better represents when the types
are actually expected to be available and usable. Switch our
compiler-builtins and libm configuration to use this by probing `rustc`
for the target's settings.
A few small `cfg` fixes are needed with this.
		
	
			
		
			
				
	
	
		
			120 lines
		
	
	
		
			4.5 KiB
		
	
	
	
		
			Rust
		
	
	
	
	
	
			
		
		
	
	
			120 lines
		
	
	
		
			4.5 KiB
		
	
	
	
		
			Rust
		
	
	
	
	
	
use std::collections::HashSet;
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mod builtins_configure {
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    include!("../compiler-builtins/configure.rs");
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}
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/// Features to enable
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#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
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enum Feature {
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    NoSysF128,
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    NoSysF128IntConvert,
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    NoSysF16,
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    NoSysF16F64Convert,
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    NoSysF16F128Convert,
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}
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impl Feature {
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    fn implies(self) -> &'static [Self] {
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        match self {
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            Self::NoSysF128 => [Self::NoSysF128IntConvert, Self::NoSysF16F128Convert].as_slice(),
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            Self::NoSysF128IntConvert => [].as_slice(),
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            Self::NoSysF16 => [Self::NoSysF16F64Convert, Self::NoSysF16F128Convert].as_slice(),
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            Self::NoSysF16F64Convert => [].as_slice(),
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            Self::NoSysF16F128Convert => [].as_slice(),
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        }
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    }
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}
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fn main() {
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    println!("cargo::rerun-if-changed=../configure.rs");
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    let target = builtins_configure::Target::from_env();
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    let mut features = HashSet::new();
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    // These platforms do not have f128 symbols available in their system libraries, so
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    // skip related tests.
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    if target.arch == "arm"
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        || target.vendor == "apple"
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        || target.env == "msvc"
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        // GCC and LLVM disagree on the ABI of `f16` and `f128` with MinGW. See
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        // <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115054>.
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        || (target.os == "windows" && target.env == "gnu")
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        // FIXME(llvm): There is an ABI incompatibility between GCC and Clang on 32-bit x86.
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        // See <https://github.com/llvm/llvm-project/issues/77401>.
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        || target.arch == "x86"
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        // 32-bit PowerPC and 64-bit LE gets code generated that Qemu cannot handle. See
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        // <https://github.com/rust-lang/compiler-builtins/pull/606#issuecomment-2105635926>.
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        || target.arch == "powerpc"
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        || target.arch == "powerpc64le"
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        // FIXME: We get different results from the builtin functions. See
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        // <https://github.com/rust-lang/compiler-builtins/pull/606#issuecomment-2105657287>.
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        || target.arch == "powerpc64"
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    {
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        features.insert(Feature::NoSysF128);
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    }
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    if target.arch == "x86" {
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        // 32-bit x86 does not have `__fixunstfti`/`__fixtfti` but does have everything else
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        features.insert(Feature::NoSysF128IntConvert);
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        // FIXME: 32-bit x86 has a bug in `f128 -> f16` system libraries
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        features.insert(Feature::NoSysF16F128Convert);
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    }
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    // These platforms do not have f16 symbols available in their system libraries, so
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    // skip related tests. Most of these are missing `f16 <-> f32` conversion routines.
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    if (target.arch == "aarch64" && target.os == "linux")
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        || target.arch.starts_with("arm")
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        || target.arch == "powerpc"
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        || target.arch == "powerpc64"
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        || target.arch == "powerpc64le"
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        || target.arch == "loongarch64"
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        || (target.arch == "x86" && !target.has_feature("sse"))
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        || target.os == "windows"
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        // Linking says "error: function signature mismatch: __extendhfsf2" and seems to
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        // think the signature is either `(i32) -> f32` or `(f32) -> f32`. See
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        // <https://github.com/llvm/llvm-project/issues/96438>.
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        || target.arch == "wasm32"
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        || target.arch == "wasm64"
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    {
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        features.insert(Feature::NoSysF16);
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    }
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    // These platforms are missing either `__extendhfdf2` or `__truncdfhf2`.
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    if target.vendor == "apple" || target.os == "windows" {
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        features.insert(Feature::NoSysF16F64Convert);
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    }
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    // Add implied features. Collection is required for borrows.
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    features.extend(
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        features
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            .iter()
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            .flat_map(|x| x.implies())
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            .copied()
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            .collect::<Vec<_>>(),
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    );
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    for feature in features {
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        let (name, warning) = match feature {
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            Feature::NoSysF128 => ("no-sys-f128", "using apfloat fallback for f128"),
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            Feature::NoSysF128IntConvert => (
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                "no-sys-f128-int-convert",
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                "using apfloat fallback for f128 <-> int conversions",
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            ),
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            Feature::NoSysF16F64Convert => (
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                "no-sys-f16-f64-convert",
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                "using apfloat fallback for f16 <-> f64 conversions",
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            ),
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            Feature::NoSysF16F128Convert => (
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                "no-sys-f16-f128-convert",
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                "using apfloat fallback for f16 <-> f128 conversions",
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            ),
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            Feature::NoSysF16 => ("no-sys-f16", "using apfloat fallback for f16"),
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        };
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        println!("cargo:warning={warning}");
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        println!("cargo:rustc-cfg=feature=\"{name}\"");
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    }
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    builtins_configure::configure_aliases(&target);
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}
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