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Update frametable printer to handle alloc calls + skip musttail calls for statepoints #23

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Merged
usuyus merged 4 commits into from
Sep 25, 2025
Merged

Update frametable printer to handle alloc calls + skip musttail calls for statepoints #23

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f9a3ade
alloc entries in frametables + disable musttail in RS4GC
usuyus Sep 24, 2025
11d8151
handle bigger allocs
usuyus Sep 25, 2025
c347f37
typos
usuyus Sep 25, 2025
81cb60d
c stack args cc + use stack offset only when we have dynamic objects
usuyus Sep 25, 2025
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29 changes: 27 additions & 2 deletions llvm/lib/CodeGen/AsmPrinter/OxCamlGCPrinter.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -140,6 +140,20 @@ static unsigned mapLLVMDwarfRegToOxCamlIndex(unsigned DwarfRegNum) {
}
}

static uint64_t stackOffsetOfID(uint64_t ID) {
return ID & ((1ull << 16) - 1) & ~(1ull);
}

static uint64_t allocSizeOfID(uint64_t ID) {
return ID >> 16;
}

static bool IDHasAlloc(uint64_t ID) {
return ID & 1ull;
}

static const int allocMask = 2;

bool OxCamlGCMetadataPrinter::emitStackMaps(Module &M, StackMaps &SM, AsmPrinter &AP) {
MCStreamer &OS = *AP.OutStreamer;
unsigned PtrSize = M.getDataLayout().getPointerSize(); // Can only be 8 for now
Expand Down Expand Up @@ -173,10 +187,16 @@ bool OxCamlGCMetadataPrinter::emitStackMaps(Module &M, StackMaps &SM, AsmPrinter

// frame_data
uint64_t FrameSize = CSI.CSFunctionInfo.StaticStackSize;
if (CSI.ID != StatepointDirectives::DefaultStatepointID)
FrameSize += CSI.ID; // Stack offset from OxCaml
FrameSize += PtrSize; // Return address

if (CSI.ID != StatepointDirectives::DefaultStatepointID) {
// Alloc bit
if (IDHasAlloc(CSI.ID)) FrameSize |= allocMask;

// Stack offset from OxCaml
FrameSize += stackOffsetOfID(CSI.ID);
}

if (FrameSize >= 1 << 16)
report_fatal_error("Long frames not supported for OxCaml GC: FrameSize = "
+ Twine(FrameSize));
Expand Down Expand Up @@ -238,6 +258,11 @@ bool OxCamlGCMetadataPrinter::emitStackMaps(Module &M, StackMaps &SM, AsmPrinter
OS.emitInt16(EncodedReg);
}

if (IDHasAlloc(CSI.ID)) {
OS.emitInt8(1);
OS.emitInt8(allocSizeOfID(CSI.ID));
}

OS.emitValueToAlignment(Align(PtrSize));
}

Expand Down
5 changes: 5 additions & 0 deletions llvm/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3087,6 +3087,11 @@ bool RewriteStatepointsForGC::runOnFunction(Function &F, DominatorTree &DT,
"Don't expect any other calls here!");
return false;
}

// `musttail` calls wrapped in statepoints fail to verify due to
// the intrinsic using variadic arguments.
if (Call->isMustTailCall()) return false;

return true;
}
return false;
Expand Down