Recommit "[AArch64][GlobalISel] Implement widenScalar for signed overflow"
Implement widening for G_SADDO and G_SSUBO.
Add legalize-add/sub tests for narrow overflowing add/sub on AArch64.
Differential Revision: https://reviews.llvm.org/D95034
diff --git a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
index b9e3225..aef9e6f 100644
--- a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
@@ -1814,6 +1814,26 @@
return widenScalarMergeValues(MI, TypeIdx, WideTy);
case TargetOpcode::G_UNMERGE_VALUES:
return widenScalarUnmergeValues(MI, TypeIdx, WideTy);
+ case TargetOpcode::G_SADDO:
+ case TargetOpcode::G_SSUBO: {
+ if (TypeIdx == 1)
+ return UnableToLegalize; // TODO
+ auto LHSExt = MIRBuilder.buildSExt(WideTy, MI.getOperand(2));
+ auto RHSExt = MIRBuilder.buildSExt(WideTy, MI.getOperand(3));
+ unsigned Opcode = MI.getOpcode() == TargetOpcode::G_SADDO
+ ? TargetOpcode::G_ADD
+ : TargetOpcode::G_SUB;
+ auto NewOp = MIRBuilder.buildInstr(Opcode, {WideTy}, {LHSExt, RHSExt});
+ LLT OrigTy = MRI.getType(MI.getOperand(0).getReg());
+ auto TruncOp = MIRBuilder.buildTrunc(OrigTy, NewOp);
+ auto ExtOp = MIRBuilder.buildSExt(WideTy, TruncOp);
+ // There is no overflow if the re-extended result is the same as NewOp.
+ MIRBuilder.buildICmp(CmpInst::ICMP_NE, MI.getOperand(1), NewOp, ExtOp);
+ // Now trunc the NewOp to the original result.
+ MIRBuilder.buildTrunc(MI.getOperand(0), NewOp);
+ MI.eraseFromParent();
+ return Legalized;
+ }
case TargetOpcode::G_UADDO:
case TargetOpcode::G_USUBO: {
if (TypeIdx == 1)
