[IR] Add a dedicated FNeg IR Instruction

The IEEE-754 Standard makes it clear that fneg(x) and
fsub(-0.0, x) are two different operations. The former is a bitwise
operation, while the latter is an arithmetic operation. This patch
creates a dedicated FNeg IR Instruction to model that behavior.

Differential Revision: https://reviews.llvm.org/D53877

llvm-svn: 346774

1 files changed, 7 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp b/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
index ef090777726..0a41877839a 100644
--- a/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
@@ -330,6 +330,13 @@ bool IRTranslator::translateFSub(const User &U, MachineIRBuilder &MIRBuilder) {
   return translateBinaryOp(TargetOpcode::G_FSUB, U, MIRBuilder);
 }
 
+bool IRTranslator::translateFNeg(const User &U, MachineIRBuilder &MIRBuilder) {
+  MIRBuilder.buildInstr(TargetOpcode::G_FNEG)
+      .addDef(getOrCreateVReg(U))
+      .addUse(getOrCreateVReg(*U.getOperand(1)));
+  return true;
+}
+
 bool IRTranslator::translateCompare(const User &U,
                                     MachineIRBuilder &MIRBuilder) {
   const CmpInst *CI = dyn_cast<CmpInst>(&U);