[GlobalISel] Translate floating-point negation

Reviewers: qcolombet, javed.absar, aditya_nandakumar, dsanders, t.p.northover, ab

Reviewed By: qcolombet

Subscribers: dberris, rovka, llvm-commits, kristof.beyls

Differential Revision: https://reviews.llvm.org/D30671

llvm-svn: 297171

1 files changed, 12 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp b/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
index 0470b3af7f5..70333057a76 100644
--- a/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
@@ -171,6 +171,18 @@ bool IRTranslator::translateBinaryOp(unsigned Opcode, const User &U,
   return true;
 }
 
+bool IRTranslator::translateFSub(const User &U, MachineIRBuilder &MIRBuilder) {
+  // -0.0 - X --> G_FNEG
+  if (isa<Constant>(U.getOperand(0)) &&
+      U.getOperand(0) == ConstantFP::getZeroValueForNegation(U.getType())) {
+    MIRBuilder.buildInstr(TargetOpcode::G_FNEG)
+        .addDef(getOrCreateVReg(U))
+        .addUse(getOrCreateVReg(*U.getOperand(1)));
+    return true;
+  }
+  return translateBinaryOp(TargetOpcode::G_FSUB, U, MIRBuilder);
+}
+
 bool IRTranslator::translateCompare(const User &U,
                                     MachineIRBuilder &MIRBuilder) {
   const CmpInst *CI = dyn_cast<CmpInst>(&U);