[GlobalISel] Add default action for G_FNEG
Summary: rL297171 introduced G_FNEG for floating-point negation instruction and IRTranslator started to translate `FSUB -0.0, X` to `FNEG X`. This patch adds a default action for G_FNEG to avoid breaking existing targets.
Reviewers: qcolombet, ab, kristof.beyls, t.p.northover, aditya_nandakumar, dsanders
Reviewed By: qcolombet
Subscribers: dberris, rovka, llvm-commits
Differential Revision: https://reviews.llvm.org/D30721
llvm-svn: 297301
diff --git a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
index 6e83270..b4decb1 100644
--- a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
@@ -539,6 +539,38 @@
MI.eraseFromParent();
return Legalized;
}
+ case TargetOpcode::G_FNEG: {
+ // TODO: Handle vector types once we are able to
+ // represent them.
+ if (Ty.isVector())
+ return UnableToLegalize;
+ unsigned Res = MI.getOperand(0).getReg();
+ Type *ZeroTy;
+ LLVMContext &Ctx = MIRBuilder.getMF().getFunction()->getContext();
+ switch (Ty.getSizeInBits()) {
+ case 16:
+ ZeroTy = Type::getHalfTy(Ctx);
+ break;
+ case 32:
+ ZeroTy = Type::getFloatTy(Ctx);
+ break;
+ case 64:
+ ZeroTy = Type::getDoubleTy(Ctx);
+ break;
+ default:
+ llvm_unreachable("unexpected floating-point type");
+ }
+ ConstantFP &ZeroForNegation =
+ *cast<ConstantFP>(ConstantFP::getZeroValueForNegation(ZeroTy));
+ unsigned Zero = MRI.createGenericVirtualRegister(Ty);
+ MIRBuilder.buildFConstant(Zero, ZeroForNegation);
+ MIRBuilder.buildInstr(TargetOpcode::G_FSUB)
+ .addDef(Res)
+ .addUse(Zero)
+ .addUse(MI.getOperand(1).getReg());
+ MI.eraseFromParent();
+ return Legalized;
+ }
}
}