GlobalISel: IRTranslate llvm.fabs.* intrinsic

Summary:
Fabs is a common floating-point operation, especially for some expansions. This patch adds
a new generic opcode for llvm.fabs.* intrinsic in order to avoid building/matching this intrinsic.

Reviewers: qcolombet, aditya_nandakumar, dsanders, rovka

Reviewed By: aditya_nandakumar

Subscribers: kristof.beyls, javed.absar, llvm-commits

Differential Revision: https://reviews.llvm.org/D43864

llvm-svn: 326749

include/llvm/CodeGen/GlobalISel/MIPatternMatch.h

@@ -286,6 +286,11 @@ m_GFPTrunc(const SrcTy &Src) {
   return UnaryOp_match<SrcTy, TargetOpcode::G_FPTRUNC>(Src);
 }
 
+template <typename SrcTy>
+inline UnaryOp_match<SrcTy, TargetOpcode::G_FABS> m_GFabs(const SrcTy &Src) {
+  return UnaryOp_match<SrcTy, TargetOpcode::G_FABS>(Src);
+}
+
 template <typename SrcTy>
 inline UnaryOp_match<SrcTy, TargetOpcode::COPY> m_Copy(SrcTy &&Src) {
   return UnaryOp_match<SrcTy, TargetOpcode::COPY>(std::forward<SrcTy>(Src));

include/llvm/CodeGen/TargetOpcodes.def

@@ -427,6 +427,9 @@ HANDLE_TARGET_OPCODE(G_SITOFP)
 /// Generic unsigned-int to float conversion
 HANDLE_TARGET_OPCODE(G_UITOFP)
 
+/// Generic FP absolute value.
+HANDLE_TARGET_OPCODE(G_FABS)
+
 /// Generic pointer offset
 HANDLE_TARGET_OPCODE(G_GEP)
 

include/llvm/Target/GenericOpcodes.td

@@ -378,6 +378,12 @@ def G_UITOFP : GenericInstruction {
   let hasSideEffects = 0;
 }
 
+def G_FABS : GenericInstruction {
+  let OutOperandList = (outs type0:$dst);
+  let InOperandList = (ins type0:$src);
+  let hasSideEffects = 0;
+}
+
 //------------------------------------------------------------------------------
 // Floating Point Binary ops.
 //------------------------------------------------------------------------------

lib/CodeGen/GlobalISel/IRTranslator.cpp

@@ -746,6 +746,11 @@ bool IRTranslator::translateKnownIntrinsic(const CallInst &CI, Intrinsic::ID ID,
         .addDef(getOrCreateVReg(CI))
         .addUse(getOrCreateVReg(*CI.getArgOperand(0)));
     return true;
+  case Intrinsic::fabs:
+    MIRBuilder.buildInstr(TargetOpcode::G_FABS)
+        .addDef(getOrCreateVReg(CI))
+        .addUse(getOrCreateVReg(*CI.getArgOperand(0)));
+    return true;
   case Intrinsic::fma:
     MIRBuilder.buildInstr(TargetOpcode::G_FMA)
         .addDef(getOrCreateVReg(CI))

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

@@ -1318,6 +1318,17 @@ define float @test_log2_intrin(float %a) {
   %res = call float @llvm.log2.f32(float %a)
   ret float %res
 }
+
+declare float @llvm.fabs.f32(float)
+define float @test_fabs_intrin(float %a) {
+; CHECK-LABEL: name: test_fabs_intrin
+; CHECK: [[A:%[0-9]+]]:_(s32) = COPY $s0
+; CHECK: [[RES:%[0-9]+]]:_(s32) = G_FABS [[A]]
+; CHECK: $s0 = COPY [[RES]]
+  %res = call float @llvm.fabs.f32(float %a)
+  ret float %res
+}
+
 declare void @llvm.lifetime.start.p0i8(i64, i8*)
 declare void @llvm.lifetime.end.p0i8(i64, i8*)
 define void @test_lifetime_intrin() {

unittests/CodeGen/GlobalISel/PatternMatchTest.cpp

@@ -230,6 +230,35 @@ TEST(PatternMatchInstr, MatchBinaryOp) {
   ASSERT_EQ(Src1, Copies[1]);
 }
 
+TEST(PatternMatchInstr, MatchFPUnaryOp) {
+  LLVMContext Context;
+  std::unique_ptr<TargetMachine> TM = createTargetMachine();
+  if (!TM)
+    return;
+  auto ModuleMMIPair = createDummyModule(Context, *TM, "");
+  MachineFunction *MF =
+      getMFFromMMI(ModuleMMIPair.first.get(), ModuleMMIPair.second.get());
+  SmallVector<unsigned, 4> Copies;
+  collectCopies(Copies, MF);
+  MachineBasicBlock *EntryMBB = &*MF->begin();
+  MachineIRBuilder B(*MF);
+  MachineRegisterInfo &MRI = MF->getRegInfo();
+  B.setInsertPt(*EntryMBB, EntryMBB->end());
+
+  // Truncate s64 to s32.
+  LLT s32 = LLT::scalar(32);
+  auto Copy0s32 = B.buildFPTrunc(s32, Copies[0]);
+
+  // Match G_FABS.
+  auto MIBFabs = B.buildInstr(TargetOpcode::G_FABS, s32, Copy0s32);
+  bool match = mi_match(MIBFabs->getOperand(0).getReg(), MRI, m_GFabs(m_Reg()));
+  ASSERT_TRUE(match);
+  unsigned Src;
+  match = mi_match(MIBFabs->getOperand(0).getReg(), MRI, m_GFabs(m_Reg(Src)));
+  ASSERT_TRUE(match);
+  ASSERT_EQ(Src, Copy0s32->getOperand(0).getReg());
+}
+
 TEST(PatternMatchInstr, MatchExtendsTrunc) {
   LLVMContext Context;
   std::unique_ptr<TargetMachine> TM = createTargetMachine();