[GlobalISel] fix crash in narrowScalarExtract if DstRegs only has one register
Summary: When narrowing a scalar G_EXTRACT where the destination lines up perfectly with a single result of the emitted G_UNMERGE_VALUES a COPY should be emitted instead of unconditionally trying to emit a G_MERGE_VALUES.
Reviewers: arsenm, dsanders
Reviewed By: arsenm
Subscribers: wdng, rovka, hiraditya, volkan, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D75743
diff --git a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
index 6384cc9..d0a51ed 100644
--- a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
@@ -3703,10 +3703,12 @@
}
Register DstReg = MI.getOperand(0).getReg();
- if(MRI.getType(DstReg).isVector())
+ if (MRI.getType(DstReg).isVector())
MIRBuilder.buildBuildVector(DstReg, DstRegs);
- else
+ else if (DstRegs.size() > 1)
MIRBuilder.buildMerge(DstReg, DstRegs);
+ else
+ MIRBuilder.buildCopy(DstReg, DstRegs[0]);
MI.eraseFromParent();
return Legalized;
}