[llvm] r339176 - [InstSimplify] fold fsub+fadd with common operand

[Sanjay Patel via llvm-commits]

Author: spatel
Date: Tue Aug  7 13:32:55 2018
New Revision: 339176

URL: http://llvm.org/viewvc/llvm-project?rev=339176&view=rev
Log:
[InstSimplify] fold fsub+fadd with common operand

Modified:
    llvm/trunk/lib/Analysis/InstructionSimplify.cpp
    llvm/trunk/test/Transforms/InstSimplify/floating-point-arithmetic.ll

Modified: llvm/trunk/lib/Analysis/InstructionSimplify.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/InstructionSimplify.cpp?rev=339176&r1=339175&r2=339176&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/InstructionSimplify.cpp (original)
+++ llvm/trunk/lib/Analysis/InstructionSimplify.cpp Tue Aug  7 13:32:55 2018
@@ -4359,6 +4359,14 @@ static Value *SimplifyFAddInst(Value *Op
                        match(Op1, m_FSub(m_AnyZeroFP(), m_Specific(Op0)))))
     return ConstantFP::getNullValue(Op0->getType());
 
+  // (X - Y) + Y --> X
+  // Y + (X - Y) --> X
+  Value *X;
+  if (FMF.noSignedZeros() && FMF.allowReassoc() &&
+      (match(Op0, m_FSub(m_Value(X), m_Specific(Op1))) ||
+       match(Op1, m_FSub(m_Value(X), m_Specific(Op0)))))
+    return X;
+
   return nullptr;
 }
 

Modified: llvm/trunk/test/Transforms/InstSimplify/floating-point-arithmetic.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstSimplify/floating-point-arithmetic.ll?rev=339176&r1=339175&r2=339176&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstSimplify/floating-point-arithmetic.ll (original)
+++ llvm/trunk/test/Transforms/InstSimplify/floating-point-arithmetic.ll Tue Aug  7 13:32:55 2018
@@ -849,9 +849,7 @@ define float @fadd_fsub_common_op_wrong_
 
 define <2 x float> @fsub_fadd_common_op_vec(<2 x float> %x, <2 x float> %y) {
 ; CHECK-LABEL: @fsub_fadd_common_op_vec(
-; CHECK-NEXT:    [[S:%.*]] = fsub <2 x float> [[X:%.*]], [[Y:%.*]]
-; CHECK-NEXT:    [[R:%.*]] = fadd reassoc nsz <2 x float> [[Y]], [[S]]
-; CHECK-NEXT:    ret <2 x float> [[R]]
+; CHECK-NEXT:    ret <2 x float> [[X:%.*]]
 ;
   %s = fsub <2 x float> %x, %y
   %r = fadd reassoc nsz <2 x float> %y, %s
@@ -862,9 +860,7 @@ define <2 x float> @fsub_fadd_common_op_
 
 define float @fsub_fadd_common_op_commute(float %x, float %y) {
 ; CHECK-LABEL: @fsub_fadd_common_op_commute(
-; CHECK-NEXT:    [[S:%.*]] = fsub float [[X:%.*]], [[Y:%.*]]
-; CHECK-NEXT:    [[R:%.*]] = fadd reassoc nsz float [[S]], [[Y]]
-; CHECK-NEXT:    ret float [[R]]
+; CHECK-NEXT:    ret float [[X:%.*]]
 ;
   %s = fsub float %x, %y
   %r = fadd reassoc nsz float %s, %y