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

[Andrea Di Biagio]

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
+