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Kyle Huey 652b502d9c Reorder stack spills so that constants come later.
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
2024-09-17 16:45:26 -07:00
.github Update library/Cargo.toml in weekly job 2024-08-19 07:30:11 -05:00
compiler Reorder stack spills so that constants come later. 2024-09-17 16:45:26 -07:00
library Auto merge of #130483 - matthiaskrgr:rollup-q1r0g0y, r=matthiaskrgr 2024-09-17 19:37:03 +00:00
LICENSES Rename LICENSES/GPL-2.0.txt into LICENSES/GPL-2.0-only.txt 2024-09-06 16:01:46 +02:00
src Auto merge of #130483 - matthiaskrgr:rollup-q1r0g0y, r=matthiaskrgr 2024-09-17 19:37:03 +00:00
tests Reorder stack spills so that constants come later. 2024-09-17 16:45:26 -07:00
.clang-format Add .clang-format 2024-06-26 05:56:00 +08:00
.editorconfig
.git-blame-ignore-revs Exclude the copy blessing from git blame 2024-08-18 16:09:03 -07:00
.gitattributes
.gitignore gitignore: ignore ICE reports regardless of directory 2024-08-25 14:19:05 +03:00
.gitmodules Make gcc submodule shallow 2024-09-06 16:01:47 +02:00
.ignore Add .ignore file to make config.toml searchable in vscode 2024-06-24 10:15:16 +02:00
.mailmap Rollup merge of #129906 - BoxyUwU:boxy_mailmap, r=lqd 2024-09-02 22:35:23 +02:00
Cargo.lock update lockfile 2024-09-17 15:20:50 +02:00
Cargo.toml Switch to using the v2 resolver in most workspaces 2024-08-18 13:59:09 -05:00
CODE_OF_CONDUCT.md
config.example.toml document dist.vendor in config.example.toml 2024-09-15 12:23:05 +03:00
configure Ensure ./configure works when configure.py path contains spaces 2024-02-16 18:57:22 +00:00
CONTRIBUTING.md
COPYRIGHT
INSTALL.md Rollup merge of #127434 - onur-ozkan:use-bootstrap-instead-of-rustbuild, r=Mark-Simulacrum 2024-07-13 20:19:45 -07:00
LICENSE-APACHE
LICENSE-MIT
README.md Use SVG logos in the README.md. 2024-04-03 19:48:20 +02:00
RELEASES.md Rollup merge of #129995 - alexcrichton:remove-wasm32-wasip2-release-notes, r=pietroalbini 2024-09-06 07:33:58 +02:00
REUSE.toml Fix licensing information in REUSE.toml 2024-09-06 16:01:47 +02:00
rust-bors.toml Increase timeout for new bors bot 2024-03-13 08:31:07 +01:00
rustfmt.toml Remove src/gcc from rustfmt checks 2024-09-06 16:01:46 +02:00
triagebot.toml notify Miri when intrinsics are changed 2024-09-11 16:31:05 +02:00
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