ValueTracking: Look through fabs and fneg in isKnownNeverInfinity

Author: arsenm

llvm/lib/Analysis/ValueTracking.cpp

@@ -3778,6 +3778,7 @@ bool llvm::isKnownNeverInfinity(const Value *V, const TargetLibraryInfo *TLI,
       Type *FPTy = Inst->getType()->getScalarType();
       return ilogb(APFloat::getLargest(FPTy->getFltSemantics())) >= IntSize;
     }
+    case Instruction::FNeg:
     case Instruction::FPExt: {
       // Peek through to source op. If it is not infinity, this is not infinity.
       return isKnownNeverInfinity(Inst->getOperand(0), TLI, Depth + 1);
@@ -3788,6 +3789,7 @@ bool llvm::isKnownNeverInfinity(const Value *V, const TargetLibraryInfo *TLI,
 
     if (const auto *II = dyn_cast<IntrinsicInst>(V)) {
       switch (II->getIntrinsicID()) {
+      case Intrinsic::fabs:
       case Intrinsic::canonicalize:
         return isKnownNeverInfinity(Inst->getOperand(0), TLI, Depth + 1);
       default:

llvm/test/Transforms/InstSimplify/floating-point-compare.ll

@@ -1283,3 +1283,45 @@ define i1 @isNotKnownNeverInfinity_canonicalize(double %x) {
   %r = fcmp une double %e, 0x7ff0000000000000
   ret i1 %r
 }
+
+define i1 @isKnownNeverInfinity_fabs(double %x) {
+; CHECK-LABEL: @isKnownNeverInfinity_fabs(
+; CHECK-NEXT:    ret i1 true
+;
+  %a = fadd ninf double %x, 1.0
+  %e = call double @llvm.fabs.f64(double %a)
+  %r = fcmp une double %e, 0x7ff0000000000000
+  ret i1 %r
+}
+
+define i1 @isNotKnownNeverInfinity_fabs(double %x) {
+; CHECK-LABEL: @isNotKnownNeverInfinity_fabs(
+; CHECK-NEXT:    [[E:%.*]] = call double @llvm.fabs.f64(double [[X:%.*]])
+; CHECK-NEXT:    [[R:%.*]] = fcmp une double [[E]], 0x7FF0000000000000
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %e = call double @llvm.fabs.f64(double %x)
+  %r = fcmp une double %e, 0x7ff0000000000000
+  ret i1 %r
+}
+
+define i1 @isKnownNeverInfinity_fneg(double %x) {
+; CHECK-LABEL: @isKnownNeverInfinity_fneg(
+; CHECK-NEXT:    ret i1 true
+;
+  %a = fadd ninf double %x, 1.0
+  %e = fneg double %a
+  %r = fcmp une double %e, 0x7ff0000000000000
+  ret i1 %r
+}
+
+define i1 @isNotKnownNeverInfinity_fneg(double %x) {
+; CHECK-LABEL: @isNotKnownNeverInfinity_fneg(
+; CHECK-NEXT:    [[E:%.*]] = fneg double [[X:%.*]]
+; CHECK-NEXT:    [[R:%.*]] = fcmp une double [[E]], 0x7FF0000000000000
+; CHECK-NEXT:    ret i1 [[R]]
+;
+  %e = fneg double %x
+  %r = fcmp une double %e, 0x7ff0000000000000
+  ret i1 %r
+}