652b502d9c
Currently constants are "pulled forward" and have their stack spills emitted first. This confuses LLVM as to where to place breakpoints at function entry, and results in argument values being wrong in the debugger. It's straightforward to avoid emitting the stack spills for constants until arguments/etc have been introduced in debug_introduce_locals, so do that. Example LLVM IR (irrelevant IR elided): Before: define internal void @_ZN11rust_1289457binding17h2c78f956ba4bd2c3E(i64 %a, i64 %b, double %c) unnamed_addr #0 !dbg !178 { start: %c.dbg.spill = alloca [8 x i8], align 8 %b.dbg.spill = alloca [8 x i8], align 8 %a.dbg.spill = alloca [8 x i8], align 8 %x.dbg.spill = alloca [4 x i8], align 4 store i32 0, ptr %x.dbg.spill, align 4, !dbg !192 ; LLVM places breakpoint here. #dbg_declare(ptr %x.dbg.spill, !190, !DIExpression(), !192) store i64 %a, ptr %a.dbg.spill, align 8 #dbg_declare(ptr %a.dbg.spill, !187, !DIExpression(), !193) store i64 %b, ptr %b.dbg.spill, align 8 #dbg_declare(ptr %b.dbg.spill, !188, !DIExpression(), !194) store double %c, ptr %c.dbg.spill, align 8 #dbg_declare(ptr %c.dbg.spill, !189, !DIExpression(), !195) ret void, !dbg !196 } After: define internal void @_ZN11rust_1289457binding17h2c78f956ba4bd2c3E(i64 %a, i64 %b, double %c) unnamed_addr #0 !dbg !178 { start: %x.dbg.spill = alloca [4 x i8], align 4 %c.dbg.spill = alloca [8 x i8], align 8 %b.dbg.spill = alloca [8 x i8], align 8 %a.dbg.spill = alloca [8 x i8], align 8 store i64 %a, ptr %a.dbg.spill, align 8 #dbg_declare(ptr %a.dbg.spill, !187, !DIExpression(), !192) store i64 %b, ptr %b.dbg.spill, align 8 #dbg_declare(ptr %b.dbg.spill, !188, !DIExpression(), !193) store double %c, ptr %c.dbg.spill, align 8 #dbg_declare(ptr %c.dbg.spill, !189, !DIExpression(), !194) store i32 0, ptr %x.dbg.spill, align 4, !dbg !195 ; LLVM places breakpoint here. #dbg_declare(ptr %x.dbg.spill, !190, !DIExpression(), !195) ret void, !dbg !196 } Note in particular the position of the "LLVM places breakpoint here" comment relative to the stack spills for the function arguments. LLVM assumes that the first instruction with with a debug location is the end of the prologue. As LLVM does not currently offer front ends any direct control over the placement of the prologue end reordering the IR is the only mechanism available to fix argument values at function entry in the presence of MIR optimizations like SingleUseConsts. Fixes #128945
This is the main source code repository for Rust. It contains the compiler, standard library, and documentation.
Why Rust?
-
Performance: Fast and memory-efficient, suitable for critical services, embedded devices, and easily integrate with other languages.
-
Reliability: Our rich type system and ownership model ensure memory and thread safety, reducing bugs at compile-time.
-
Productivity: Comprehensive documentation, a compiler committed to providing great diagnostics, and advanced tooling including package manager and build tool (Cargo), auto-formatter (rustfmt), linter (Clippy) and editor support (rust-analyzer).
Quick Start
Read "Installation" from The Book.
Installing from Source
If you really want to install from source (though this is not recommended), see INSTALL.md.
Getting Help
See https://www.rust-lang.org/community for a list of chat platforms and forums.
Contributing
See CONTRIBUTING.md.
License
Rust is primarily distributed under the terms of both the MIT license and the Apache License (Version 2.0), with portions covered by various BSD-like licenses.
See LICENSE-APACHE, LICENSE-MIT, and COPYRIGHT for details.
Trademark
The Rust Foundation owns and protects the Rust and Cargo trademarks and logos (the "Rust Trademarks").
If you want to use these names or brands, please read the media guide.
Third-party logos may be subject to third-party copyrights and trademarks. See Licenses for details.