[InstCombine] Handle more fp op/intrinsics

Author: dtcxzyw

llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp

@@ -2782,16 +2782,31 @@ static bool ignoreSignBitOfZero(Instruction &I) {
   // Check if the sign bit is ignored by the only user.
   if (!I.hasOneUse())
     return false;
-  Instruction *User = I.user_back();
-
-  // fcmp treats both positive and negative zero as equal.
-  if (User->getOpcode() == Instruction::FCmp)
+  auto *FPOp = dyn_cast<FPMathOperator>(I.user_back());
+  if (!FPOp)
+    return false;
+  if (FPOp->hasNoSignedZeros())
     return true;
 
-  if (auto *FPOp = dyn_cast<FPMathOperator>(User))
-    return FPOp->hasNoSignedZeros();
-
-  return false;
+  switch (FPOp->getOpcode()) {
+  case Instruction::FCmp:
+    // fcmp treats both positive and negative zero as equal.
+    return true;
+  case Instruction::Call:
+    if (auto *II = dyn_cast<IntrinsicInst>(FPOp)) {
+      switch (II->getIntrinsicID()) {
+      case Intrinsic::fabs:
+        return true;
+      case Intrinsic::copysign:
+        return II->getArgOperand(0) == &I;
+      default:
+        return false;
+      }
+    }
+    return false;
+  default:
+    return false;
+  }
 }
 
 /// Return true if the sign bit of result can be ignored when the result is NaN.
@@ -2802,16 +2817,43 @@ static bool ignoreSignBitOfNaN(Instruction &I) {
   // Check if the sign bit is ignored by the only user.
   if (!I.hasOneUse())
     return false;
-  Instruction *User = I.user_back();
-
-  // fcmp ignores the sign bit of NaN.
-  if (User->getOpcode() == Instruction::FCmp)
+  auto *FPOp = dyn_cast<FPMathOperator>(I.user_back());
+  if (!FPOp)
+    return false;
+  if (FPOp->hasNoNaNs())
     return true;
 
-  if (auto *FPOp = dyn_cast<FPMathOperator>(User))
-    return FPOp->hasNoNaNs();
-
-  return false;
+  switch (FPOp->getOpcode()) {
+  case Instruction::FNeg:
+  case Instruction::Select:
+  case Instruction::PHI:
+    return false;
+  case Instruction::Call: {
+    if (auto *II = dyn_cast<IntrinsicInst>(FPOp)) {
+      switch (II->getIntrinsicID()) {
+      case Intrinsic::fabs:
+        return true;
+      case Intrinsic::copysign:
+        return II->getArgOperand(0) == &I;
+      case Intrinsic::maxnum:
+      case Intrinsic::minnum:
+      case Intrinsic::maximum:
+      case Intrinsic::minimum:
+      case Intrinsic::maximumnum:
+      case Intrinsic::minimumnum:
+      case Intrinsic::canonicalize:
+        return false;
+      default:
+        // Other proper FP intrinsics ignore the sign bit of NaN.
+        return true;
+      }
+    }
+    return false;
+  }
+  default:
+    // Other proper FP math operations ignore the sign bit of NaN.
+    return true;
+  }
 }
 
 // Canonicalize select with fcmp to fabs(). -0.0 makes this tricky. We need

llvm/test/Transforms/InstCombine/fabs.ll

@@ -1329,35 +1329,33 @@ define float @test_fabs_fsub_used_by_fpop_nnan(float %x, float %y) {
   ret float %add
 }
 
-; Negative tests
-
-define float @test_fabs_used_by_fpop_nnan(float %x, float %y) {
-; CHECK-LABEL: @test_fabs_used_by_fpop_nnan(
-; CHECK-NEXT:    [[CMP:%.*]] = fcmp oge float [[X:%.*]], 0.000000e+00
-; CHECK-NEXT:    [[NEG:%.*]] = fneg float [[X]]
-; CHECK-NEXT:    [[SEL:%.*]] = select i1 [[CMP]], float [[X]], float [[NEG]]
-; CHECK-NEXT:    [[ADD:%.*]] = fadd nnan float [[SEL]], [[Y:%.*]]
+define float @test_fabs_used_by_fpop_nsz(float %x, float %y) {
+; CHECK-LABEL: @test_fabs_used_by_fpop_nsz(
+; CHECK-NEXT:    [[SEL:%.*]] = call float @llvm.fabs.f32(float [[X:%.*]])
+; CHECK-NEXT:    [[ADD:%.*]] = fadd nsz float [[SEL]], [[Y:%.*]]
 ; CHECK-NEXT:    ret float [[ADD]]
 ;
   %cmp = fcmp oge float %x, 0.000000e+00
   %neg = fneg float %x
   %sel = select i1 %cmp, float %x, float %neg
-  %add = fadd nnan float %sel, %y
+  %add = fadd nsz float %sel, %y
   ret float %add
 }
 
-define float @test_fabs_used_by_fpop_nsz(float %x, float %y) {
-; CHECK-LABEL: @test_fabs_used_by_fpop_nsz(
+; Negative tests
+
+define float @test_fabs_used_by_fpop_nnan(float %x, float %y) {
+; CHECK-LABEL: @test_fabs_used_by_fpop_nnan(
 ; CHECK-NEXT:    [[CMP:%.*]] = fcmp oge float [[X:%.*]], 0.000000e+00
 ; CHECK-NEXT:    [[NEG:%.*]] = fneg float [[X]]
 ; CHECK-NEXT:    [[SEL:%.*]] = select i1 [[CMP]], float [[X]], float [[NEG]]
-; CHECK-NEXT:    [[ADD:%.*]] = fadd nsz float [[SEL]], [[Y:%.*]]
+; CHECK-NEXT:    [[ADD:%.*]] = fadd nnan float [[SEL]], [[Y:%.*]]
 ; CHECK-NEXT:    ret float [[ADD]]
 ;
   %cmp = fcmp oge float %x, 0.000000e+00
   %neg = fneg float %x
   %sel = select i1 %cmp, float %x, float %neg
-  %add = fadd nsz float %sel, %y
+  %add = fadd nnan float %sel, %y
   ret float %add
 }