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MC,AMDGPU: Don't pad .text with s_code_end if it would otherwise be empty #147980

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MC,AMDGPU: Don't pad .text with s_code_end if it would otherwise be empty #147980

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9f4e8e1
AMDGPU: Don't pad .text with s_code_end if it would otherwise be empty
trenouf Feb 20, 2025
dab2b13
Use hasInstructions(), and fix hasInstructions() to work on the asm s…
trenouf Jul 11, 2025
7ab4412
Add test
trenouf Jul 11, 2025
b31739c
Fix setHasInstruction() fix
trenouf Jul 11, 2025
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4 changes: 3 additions & 1 deletion llvm/lib/Target/AMDGPU/AMDGPUAsmPrinter.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -486,10 +486,12 @@ bool AMDGPUAsmPrinter::doFinalization(Module &M) {
// Pad with s_code_end to help tools and guard against instruction prefetch
// causing stale data in caches. Arguably this should be done by the linker,
// which is why this isn't done for Mesa.
// Don't do it if there are no functions.
const MCSubtargetInfo &STI = *getGlobalSTI();
if ((AMDGPU::isGFX10Plus(STI) || AMDGPU::isGFX90A(STI)) &&
(STI.getTargetTriple().getOS() == Triple::AMDHSA ||
STI.getTargetTriple().getOS() == Triple::AMDPAL)) {
STI.getTargetTriple().getOS() == Triple::AMDPAL) &&
!M.empty()) {
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Seems reasonable but I wonder if there's a better way to test "did we emit any code?". E.g. what if the module contains some function declarations but no definitions?

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Plus this may misdetect available_externally functions which will be dropped

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I changed to using MCSection::hasInstructions(), which I had to fix to work with the asm streamer.

Also added test. The positive case (when it does add padding) already has a test.

OutStreamer->switchSection(getObjFileLowering().getTextSection());
getTargetStreamer()->EmitCodeEnd(STI);
}
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