[GlobalISel] LegalizerHelper: Lower (G_FSUB X, Y) to (G_FADD X, (G_FNEG Y))
Summary: No test case as none of the in-tree targets with GlobalISel support has this condition.
Reviewers: qcolombet, aditya_nandakumar, dsanders, t.p.northover, ab
Reviewed By: qcolombet
Subscribers: dberris, rovka, kristof.beyls, llvm-commits, igorb
Differential Revision: https://reviews.llvm.org/D30786
llvm-svn: 297512
diff --git a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
index bab92e2..af4747f 100644
--- a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
@@ -570,6 +570,24 @@
MI.eraseFromParent();
return Legalized;
}
+ case TargetOpcode::G_FSUB: {
+ // Lower (G_FSUB LHS, RHS) to (G_FADD LHS, (G_FNEG RHS)).
+ // First, check if G_FNEG is marked as Lower. If so, we may
+ // end up with an infinite loop as G_FSUB is used to legalize G_FNEG.
+ if (LI.getAction({G_FNEG, Ty}).first == LegalizerInfo::Lower)
+ return UnableToLegalize;
+ unsigned Res = MI.getOperand(0).getReg();
+ unsigned LHS = MI.getOperand(1).getReg();
+ unsigned RHS = MI.getOperand(2).getReg();
+ unsigned Neg = MRI.createGenericVirtualRegister(Ty);
+ MIRBuilder.buildInstr(TargetOpcode::G_FNEG).addDef(Neg).addUse(RHS);
+ MIRBuilder.buildInstr(TargetOpcode::G_FADD)
+ .addDef(Res)
+ .addUse(LHS)
+ .addUse(Neg);
+ MI.eraseFromParent();
+ return Legalized;
+ }
}
}
