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[GlobalOpt] Update debug info when changing CC to Fast #144303

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[GlobalOpt] Update debug info when changing CC to Fast #144303

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18 changes: 18 additions & 0 deletions llvm/lib/Transforms/IPO/GlobalOpt.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1920,6 +1920,14 @@ static void RemovePreallocated(Function *F) {
}
}

static unsigned char GetDebugInfoFastCC(const Triple &Triple) {
if (Triple.isOSWindows() && Triple.isArch32Bit()) {
return llvm::dwarf::DW_CC_BORLAND_msfastcall;
}

return llvm::dwarf::DW_CC_normal;
}

Comment on lines +1923 to +1930
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This seems a bit brittle, if other targets had other calling convention choices - perhaps this logic should go wherever the CC is determined?

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I agree. However, I think the mapping for fastcc is determined by a table definition for each architecture. I feel like integrating this there is not easily feasible.

Do you have a recommendation on how this could be done better?

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Could you point to the table definition, we/someone could take a look to see how practical it is.

static bool
OptimizeFunctions(Module &M,
function_ref<TargetLibraryInfo &(Function &)> GetTLI,
Expand All @@ -1938,6 +1946,9 @@ OptimizeFunctions(Module &M,
if (hasOnlyColdCalls(F, GetBFI, ChangeableCCCache))
AllCallsCold.push_back(&F);

unsigned char DebugInfoFastCC =
GetDebugInfoFastCC(Triple(M.getTargetTriple()));

// Optimize functions.
for (Function &F : llvm::make_early_inc_range(M)) {
// Don't perform global opt pass on naked functions; we don't want fast
Expand Down Expand Up @@ -2021,6 +2032,13 @@ OptimizeFunctions(Module &M,
// Fast calling convention.
F.setCallingConv(CallingConv::Fast);
ChangeCalleesToFastCall(&F);

if (F.getSubprogram()) {
DISubprogram *SP = F.getSubprogram();
auto Temp = SP->getType()->cloneWithCC(DebugInfoFastCC);
SP->replaceType(MDNode::replaceWithPermanent(std::move(Temp)));
}

++NumFastCallFns;
Changed = true;
}
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