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[RegAlloc] Add additional tracing in InlineSpiller::rematerializeFor #160761

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Sep 26, 2025
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[RegAlloc] Add additional tracing in InlineSpiller::rematerializeFor #160761

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13 changes: 11 additions & 2 deletions llvm/lib/CodeGen/InlineSpiller.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -642,8 +642,12 @@ bool InlineSpiller::reMaterializeFor(LiveInterval &VirtReg, MachineInstr &MI) {
SmallVector<std::pair<MachineInstr *, unsigned>, 8> Ops;
VirtRegInfo RI = AnalyzeVirtRegInBundle(MI, VirtReg.reg(), &Ops);

if (!RI.Reads)
// Defs without reads will be deleted if unused after remat is
// completed for other users of the virtual register.
if (!RI.Reads) {
LLVM_DEBUG(dbgs() << "\tskipping remat of def " << MI);
return false;
}

SlotIndex UseIdx = LIS.getInstructionIndex(MI).getRegSlot(true);
VNInfo *ParentVNI = VirtReg.getVNInfoAt(UseIdx.getBaseIndex());
Expand All @@ -657,8 +661,13 @@ bool InlineSpiller::reMaterializeFor(LiveInterval &VirtReg, MachineInstr &MI) {
return true;
}

if (SnippetCopies.count(&MI))
// Snippets copies are ignored for remat, and will be deleted if they
// don't feed a live user after rematerialization completes.
if (SnippetCopies.count(&MI)) {
LLVM_DEBUG(dbgs() << "\tskipping remat snippet copy for " << UseIdx << '\t'
<< MI);
return false;
}

LiveInterval &OrigLI = LIS.getInterval(Original);
VNInfo *OrigVNI = OrigLI.getVNInfoAt(UseIdx);
Expand Down