[llvm] r216913 - [APFloat] Fixed a bug in method 'fusedMultiplyAdd'.

[Michael Gottesman]

Can you please put in unit tests into unittests/ADT/APFloatTest.cpp at least for the test cases that you put into the .ll file?

Michael

On Sep 2, 2014, at 9:44 AM, Andrea Di Biagio <Andrea_DiBiagio at sn.scee.net> wrote:

> Author: adibiagio
> Date: Tue Sep  2 11:44:56 2014
> New Revision: 216913
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=216913&view=rev
> Log:
> [APFloat] Fixed a bug in method 'fusedMultiplyAdd'.
> 
> When folding a fused multiply-add builtin call, make sure that we propagate the
> correct result in the case where the addend is zero, and the two other operands
> are finite non-zero.
> 
> Example:
>  define double @test() {
>    %1 = call double @llvm.fma.f64(double 7.0, double 8.0, double 0.0)
>    ret double %1
>  }
> 
> Before this patch, the instruction simplifier wrongly folded the builtin call
> in function @test to constant 'double 7.0'.
> With this patch, method 'fusedMultiplyAdd' correctly evaluates the multiply and
> propagates the expected result (i.e. 56.0).
> 
> Added test fold-builtin-fma.ll with the reproducible from PR20832 plus extra
> test cases to verify the behavior of method 'fusedMultiplyAdd' in the presence
> of NaN/Inf operands.
> 
> This fixes PR20832.
> 
> Differential Revision: http://reviews.llvm.org/D5152
> 
> Added:
>    llvm/trunk/test/Transforms/InstSimplify/fold-builtin-fma.ll
> Modified:
>    llvm/trunk/lib/Support/APFloat.cpp
> 
> Modified: llvm/trunk/lib/Support/APFloat.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Support/APFloat.cpp?rev=216913&r1=216912&r2=216913&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Support/APFloat.cpp (original)
> +++ llvm/trunk/lib/Support/APFloat.cpp Tue Sep  2 11:44:56 2014
> @@ -1801,7 +1801,7 @@ APFloat::fusedMultiplyAdd(const APFloat
>      extended-precision calculation.  */
>   if (isFiniteNonZero() &&
>       multiplicand.isFiniteNonZero() &&
> -      addend.isFiniteNonZero()) {
> +      addend.isFinite()) {
>     lostFraction lost_fraction;
> 
>     lost_fraction = multiplySignificand(multiplicand, &addend);
> 
> Added: llvm/trunk/test/Transforms/InstSimplify/fold-builtin-fma.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstSimplify/fold-builtin-fma.ll?rev=216913&view=auto
> ==============================================================================
> --- llvm/trunk/test/Transforms/InstSimplify/fold-builtin-fma.ll (added)
> +++ llvm/trunk/test/Transforms/InstSimplify/fold-builtin-fma.ll Tue Sep  2 11:44:56 2014
> @@ -0,0 +1,119 @@
> +; RUN: opt -instsimplify -S < %s | FileCheck %s
> +
> +; Fixes PR20832
> +; Make sure that we correctly fold a fused multiply-add where operands
> +; are all finite constants and addend is zero.
> +
> +declare double @llvm.fma.f64(double, double, double)
> +
> +
> +define double @PR20832()  {
> +  %1 = call double @llvm.fma.f64(double 7.0, double 8.0, double 0.0)
> +  ret double %1
> +}
> +; CHECK-LABEL: @PR20832(
> +; CHECK: ret double 5.600000e+01
> +
> +; Test builtin fma with all finite non-zero constants.
> +define double @test_all_finite()  {
> +  %1 = call double @llvm.fma.f64(double 7.0, double 8.0, double 5.0)
> +  ret double %1
> +}
> +; CHECK-LABEL: @test_all_finite(
> +; CHECK: ret double 6.100000e+01
> +
> +; Test builtin fma with a +/-NaN addend.
> +define double @test_NaN_addend()  {
> +  %1 = call double @llvm.fma.f64(double 7.0, double 8.0, double 0x7FF8000000000000)
> +  ret double %1
> +}
> +; CHECK-LABEL: @test_NaN_addend(
> +; CHECK: ret double 0x7FF8000000000000
> +
> +define double @test_NaN_addend_2()  {
> +  %1 = call double @llvm.fma.f64(double 7.0, double 8.0, double 0xFFF8000000000000)
> +  ret double %1
> +}
> +; CHECK-LABEL: @test_NaN_addend_2(
> +; CHECK: ret double 0xFFF8000000000000
> +
> +; Test builtin fma with a +/-Inf addend.
> +define double @test_Inf_addend()  {
> +  %1 = call double @llvm.fma.f64(double 7.0, double 8.0, double 0x7FF0000000000000)
> +  ret double %1
> +}
> +; CHECK-LABEL: @test_Inf_addend(
> +; CHECK: ret double 0x7FF0000000000000
> +
> +define double @test_Inf_addend_2()  {
> +  %1 = call double @llvm.fma.f64(double 7.0, double 8.0, double 0xFFF0000000000000)
> +  ret double %1
> +}
> +; CHECK-LABEL: @test_Inf_addend_2(
> +; CHECK: ret double 0xFFF0000000000000
> +
> +; Test builtin fma with one of the operands to the multiply being +/-NaN.
> +define double @test_NaN_1()  {
> +  %1 = call double @llvm.fma.f64(double 0x7FF8000000000000, double 8.0, double 0.0)
> +  ret double %1
> +}
> +; CHECK-LABEL: @test_NaN_1(
> +; CHECK: ret double 0x7FF8000000000000
> +
> +
> +define double @test_NaN_2()  {
> +  %1 = call double @llvm.fma.f64(double 7.0, double 0x7FF8000000000000, double 0.0)
> +  ret double %1
> +}
> +; CHECK-LABEL: @test_NaN_2(
> +; CHECK: ret double 0x7FF8000000000000
> +
> +
> +define double @test_NaN_3()  {
> +  %1 = call double @llvm.fma.f64(double 0xFFF8000000000000, double 8.0, double 0.0)
> +  ret double %1
> +}
> +; CHECK-LABEL: @test_NaN_3(
> +; CHECK: ret double 0x7FF8000000000000
> +
> +
> +define double @test_NaN_4()  {
> +  %1 = call double @llvm.fma.f64(double 7.0, double 0xFFF8000000000000, double 0.0)
> +  ret double %1
> +}
> +; CHECK-LABEL: @test_NaN_4(
> +; CHECK: ret double 0x7FF8000000000000
> +
> +
> +; Test builtin fma with one of the operands to the multiply being +/-Inf.
> +define double @test_Inf_1()  {
> +  %1 = call double @llvm.fma.f64(double 0x7FF0000000000000, double 8.0, double 0.0)
> +  ret double %1
> +}
> +; CHECK-LABEL: @test_Inf_1(
> +; CHECK: ret double 0x7FF0000000000000
> +
> +
> +define double @test_Inf_2()  {
> +  %1 = call double @llvm.fma.f64(double 7.0, double 0x7FF0000000000000, double 0.0)
> +  ret double %1
> +}
> +; CHECK-LABEL: @test_Inf_2(
> +; CHECK: ret double 0x7FF0000000000000
> +
> +
> +define double @test_Inf_3()  {
> +  %1 = call double @llvm.fma.f64(double 0xFFF0000000000000, double 8.0, double 0.0)
> +  ret double %1
> +}
> +; CHECK-LABEL: @test_Inf_3(
> +; CHECK: ret double 0xFFF0000000000000
> +
> +
> +define double @test_Inf_4()  {
> +  %1 = call double @llvm.fma.f64(double 7.0, double 0xFFF0000000000000, double 0.0)
> +  ret double %1
> +}
> +; CHECK-LABEL: @test_Inf_4(
> +; CHECK: ret double 0xFFF0000000000000
> +
> 
> 
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