commit 0c82d9b5a2e2eaf19eeb41abaa61646f0de7bec1
author Cameron McInally <cameron.mcinally@nyu.edu> Wed May 15 14:31:33 2019 +0000
committer Cameron McInally <cameron.mcinally@nyu.edu> Wed May 15 14:31:33 2019 +0000
tree 21968e3758ea9728c82d3b041ed586ec07eb375f
parent eaf4413d2d9d598f093e8c8e84bc01dd33a089e4

Teach InstSimplify -X + X --> 0.0 about unary FNeg

Differential Revision: https://reviews.llvm.org/D61916

llvm-svn: 360777

llvm/lib/Analysis/InstructionSimplify.cpp

diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index febc1d5..770fdf9 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -4316,16 +4316,22 @@
       (FMF.noSignedZeros() || CannotBeNegativeZero(Op0, Q.TLI)))
     return Op0;
 
-  // With nnan: (+/-0.0 - X) + X --> 0.0 (and commuted variant)
+  // With nnan: -X + X --> 0.0 (and commuted variant)
   // We don't have to explicitly exclude infinities (ninf): INF + -INF == NaN.
   // Negative zeros are allowed because we always end up with positive zero:
   // X = -0.0: (-0.0 - (-0.0)) + (-0.0) == ( 0.0) + (-0.0) == 0.0
   // X = -0.0: ( 0.0 - (-0.0)) + (-0.0) == ( 0.0) + (-0.0) == 0.0
   // X =  0.0: (-0.0 - ( 0.0)) + ( 0.0) == (-0.0) + ( 0.0) == 0.0
   // X =  0.0: ( 0.0 - ( 0.0)) + ( 0.0) == ( 0.0) + ( 0.0) == 0.0
-  if (FMF.noNaNs() && (match(Op0, m_FSub(m_AnyZeroFP(), m_Specific(Op1))) ||
-                       match(Op1, m_FSub(m_AnyZeroFP(), m_Specific(Op0)))))
-    return ConstantFP::getNullValue(Op0->getType());
+  if (FMF.noNaNs()) {
+    if (match(Op0, m_FSub(m_AnyZeroFP(), m_Specific(Op1))) ||
+        match(Op1, m_FSub(m_AnyZeroFP(), m_Specific(Op0))))
+      return ConstantFP::getNullValue(Op0->getType());
+
+    if (match(Op0, m_FNeg(m_Specific(Op1))) ||
+        match(Op1, m_FNeg(m_Specific(Op0))))
+      return ConstantFP::getNullValue(Op0->getType());
+  }
 
   // (X - Y) + Y --> X
   // Y + (X - Y) --> X