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llvm: fix up clobbers for valgrind requests #25848

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Merged
merged 2 commits into from
Nov 7, 2025
Merged

llvm: fix up clobbers for valgrind requests #25848

merged 2 commits into from
Nov 7, 2025

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@Rexicon226 Rexicon226 commented Nov 7, 2025 •
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closes #25840

reasoning for adding the extra clobbers:

zig/src/codegen/llvm.zig

Lines 7506 to 7509 in 40132af

// For some targets, Clang unconditionally adds some clobbers to all inline assembly.
// While this is probably not strictly necessary, if we don't follow Clang's lead
// here then we may risk tripping LLVM bugs since anything not used by Clang tends
// to be buggy and regress often.

the edx -> rdx switch matches what we do in the stdlib:

zig/lib/std/valgrind.zig

Line 100 in 40132af

[_] "{rdx}" (default),

also makes sense since that's the x86-64 branch (prob was just copied)

@Rexicon226
llvm: clobber rdx instead of edx for x86-64 valgrind request
09e4035
@Rexicon226
llvm: add extra clobbers to valgrind requests
483f9bd 
This seems to work around a very puzzling miscompilation first
present in LLVM 21.x. We already unconditionally add these
clobbers to inline assembly that came from the source, the
valgrind requests should also contain them.
@Rexicon226 Rexicon226 changed the title llvm: clobber rdx instead of edx for x86-64 valgrind request llvm: fix up clobbers for valgrind requests Nov 7, 2025
@alexrp alexrp enabled auto-merge November 7, 2025 04:36
@Rexicon226 Rexicon226 mentioned this pull request Nov 7, 2025
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@alexrp alexrp merged commit 19af9fa into ziglang:master Nov 7, 2025
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@Rexicon226 Rexicon226 deleted the llvm-valgrind-clobber branch November 7, 2025 15:58
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Invalid elliptic curve field arithmetic with -femit-llvm-bc and >= -O1

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