[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

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@297171 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/CodeGen/GlobalISel/IRTranslator.h

@@ -206,6 +206,8 @@ class IRTranslator : public MachineFunctionPass {
   /// \pre \p U is a return instruction.
   bool translateRet(const User &U, MachineIRBuilder &MIRBuilder);
 
+  bool translateFSub(const User &U, MachineIRBuilder &MIRBuilder);
+
   bool translateAdd(const User &U, MachineIRBuilder &MIRBuilder) {
     return translateBinaryOp(TargetOpcode::G_ADD, U, MIRBuilder);
   }
@@ -288,9 +290,6 @@ class IRTranslator : public MachineFunctionPass {
   bool translateFAdd(const User &U, MachineIRBuilder &MIRBuilder) {
     return translateBinaryOp(TargetOpcode::G_FADD, U, MIRBuilder);
   }
-  bool translateFSub(const User &U, MachineIRBuilder &MIRBuilder) {
-    return translateBinaryOp(TargetOpcode::G_FSUB, U, MIRBuilder);
-  }
   bool translateFMul(const User &U, MachineIRBuilder &MIRBuilder) {
     return translateBinaryOp(TargetOpcode::G_FMUL, U, MIRBuilder);
   }

include/llvm/Target/GenericOpcodes.td

@@ -316,6 +316,12 @@ def G_SMULH : Instruction {
 // Floating Point Unary Ops.
 //------------------------------------------------------------------------------
 
+def G_FNEG : Instruction {
+  let OutOperandList = (outs type0:$dst);
+  let InOperandList = (ins type0:$src);
+  let hasSideEffects = 0;
+}
+
 def G_FPEXT : Instruction {
   let OutOperandList = (outs type0:$dst);
   let InOperandList = (ins type1:$src);

include/llvm/Target/TargetOpcodes.def

@@ -364,6 +364,9 @@ HANDLE_TARGET_OPCODE(G_FREM)
 /// Generic FP exponentiation.
 HANDLE_TARGET_OPCODE(G_FPOW)
 
+/// Generic FP negation.
+HANDLE_TARGET_OPCODE(G_FNEG)
+
 /// Generic FP extension.
 HANDLE_TARGET_OPCODE(G_FPEXT)
 

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);

test/CodeGen/AArch64/GlobalISel/arm64-irtranslator.ll

@@ -1209,3 +1209,21 @@ define void @test_load_store_atomics(i8* %addr) {
 
   ret void
 }
+
+define float @test_fneg_f32(float %x) {
+; CHECK-LABEL: name: test_fneg_f32
+; CHECK: [[ARG:%[0-9]+]](s32) = COPY %s0
+; CHECK: [[RES:%[0-9]+]](s32) = G_FNEG [[ARG]]
+; CHECK: %s0 = COPY [[RES]](s32)
+  %neg = fsub float -0.000000e+00, %x
+  ret float %neg
+}
+
+define double @test_fneg_f64(double %x) {
+; CHECK-LABEL: name: test_fneg_f64
+; CHECK: [[ARG:%[0-9]+]](s64) = COPY %d0
+; CHECK: [[RES:%[0-9]+]](s64) = G_FNEG [[ARG]]
+; CHECK: %d0 = COPY [[RES]](s64)
+  %neg = fsub double -0.000000e+00, %x
+  ret double %neg
+}