[llvm] r223270 - [SimplifyLibCalls] Improve double->float shrinking to consider constants

[Eric Christopher]

>
> +  if (ConstantFP *Const = dyn_cast<ConstantFP>(Val)) {
> +    APFloat F = Const->getValueAPF();
> +    bool loosesInfo;
>

Nit: "loses".

-eric

+    (void)F.convert(APFloat::IEEEsingle, APFloat::rmNearestTiesToEven,
> +                    &loosesInfo);
>



> +    if (!loosesInfo)
> +      return ConstantFP::get(Const->getContext(), F);
> +  }
> +  return nullptr;
> +}
> +
>  //===-------------------------------------------------------
> ---------------===//
>  // Double -> Float Shrinking Optimizations for Unary Functions like
> 'floor'
>
> @@ -1052,12 +1074,11 @@ Value *LibCallSimplifier::optimizeUnaryD
>    }
>
>    // If this is something like 'floor((double)floatval)', convert to
> floorf.
> -  FPExtInst *Cast = dyn_cast<FPExtInst>(CI->getArgOperand(0));
> -  if (!Cast || !Cast->getOperand(0)->getType()->isFloatTy())
> +  Value *V = valueHasFloatPrecision(CI->getArgOperand(0));
> +  if (V == nullptr)
>      return nullptr;
>
>    // floor((double)floatval) -> (double)floorf(floatval)
> -  Value *V = Cast->getOperand(0);
>    if (Callee->isIntrinsic()) {
>      Module *M = CI->getParent()->getParent()->getParent();
>      Intrinsic::ID IID = (Intrinsic::ID) Callee->getIntrinsicID();
> @@ -1083,21 +1104,19 @@ Value *LibCallSimplifier::optimizeBinary
>      return nullptr;
>
>    // If this is something like 'fmin((double)floatval1,
> (double)floatval2)',
> -  // we convert it to fminf.
> -  FPExtInst *Cast1 = dyn_cast<FPExtInst>(CI->getArgOperand(0));
> -  FPExtInst *Cast2 = dyn_cast<FPExtInst>(CI->getArgOperand(1));
> -  if (!Cast1 || !Cast1->getOperand(0)->getType()->isFloatTy() || !Cast2
> ||
> -      !Cast2->getOperand(0)->getType()->isFloatTy())
> +  // or fmin(1.0, (double)floatval), then we convert it to fminf.
> +  Value *V1 = valueHasFloatPrecision(CI->getArgOperand(0));
> +  if (V1 == nullptr)
> +    return nullptr;
> +  Value *V2 = valueHasFloatPrecision(CI->getArgOperand(1));
> +  if (V2 == nullptr)
>      return nullptr;
>
>    // fmin((double)floatval1, (double)floatval2)
> -  //                      -> (double)fmin(floatval1, floatval2)
> -  Value *V = nullptr;
> -  Value *V1 = Cast1->getOperand(0);
> -  Value *V2 = Cast2->getOperand(0);
> +  //                      -> (double)fminf(floatval1, floatval2)
>    // TODO: Handle intrinsics in the same way as in
> optimizeUnaryDoubleFP().
> -  V = EmitBinaryFloatFnCall(V1, V2, Callee->getName(), B,
> -                            Callee->getAttributes());
> +  Value *V = EmitBinaryFloatFnCall(V1, V2, Callee->getName(), B,
> +                                   Callee->getAttributes());
>    return B.CreateFPExt(V, B.getDoubleTy());
>  }
>
>
> Modified: llvm/trunk/test/Transforms/InstCombine/float-shrink-compare.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/
> Transforms/InstCombine/float-shrink-compare.ll?rev=223270&
> r1=223269&r2=223270&view=diff
> ============================================================
> ==================
> --- llvm/trunk/test/Transforms/InstCombine/float-shrink-compare.ll
> (original)
> +++ llvm/trunk/test/Transforms/InstCombine/float-shrink-compare.ll Wed
> Dec  3 15:46:33 2014
> @@ -235,6 +235,30 @@ define i32 @test19(float %x, float %y, f
>  ; CHECK-NEXT: fcmp oeq float %copysignf, %z
>  }
>
> +define i32 @test20(float %x, float %y) nounwind uwtable {
> +  %1 = fpext float %y to double
> +  %2 = fpext float %x to double
> +  %3 = call double @fmin(double 1.000000e+00, double %2) nounwind
> +  %4 = fcmp oeq double %1, %3
> +  %5 = zext i1 %4 to i32
> +  ret i32 %5
> +; CHECK-LABEL: @test20(
> +; CHECK-NEXT: %fminf = call float @fminf(float 1.000000e+00, float %x)
> +; CHECK-NEXT: fcmp oeq float %fminf, %y
> +}
> +
> +define i32 @test21(float %x, float %y) nounwind uwtable {
> +  %1 = fpext float %y to double
> +  %2 = fpext float %x to double
> +  %3 = call double @fmin(double 1.300000e+00, double %2) nounwind
> +  %4 = fcmp oeq double %1, %3
> +  %5 = zext i1 %4 to i32
> +  ret i32 %5
> +; should not be changed to fminf as the constant would loose precision
> +; CHECK-LABEL: @test21(
> +; CHECK: %3 = call double @fmin(double 1.300000e+00, double %2)
> +}
> +
>  declare double @fabs(double) nounwind readnone
>  declare double @ceil(double) nounwind readnone
>  declare double @copysign(double, double) nounwind readnone
>
>
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