[llvm] r329316 - [InstCombine] use pattern matchers for fsub --> fadd folds

[Sanjay Patel via llvm-commits]

Author: spatel
Date: Thu Apr  5 10:06:45 2018
New Revision: 329316

URL: http://llvm.org/viewvc/llvm-project?rev=329316&view=rev
Log:
[InstCombine] use pattern matchers for fsub --> fadd folds

This allows folding for vectors with undef elements.

Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstCombineAddSub.cpp
    llvm/trunk/test/Transforms/InstCombine/fsub.ll

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineAddSub.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineAddSub.cpp?rev=329316&r1=329315&r2=329316&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineAddSub.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineAddSub.cpp Thu Apr  5 10:06:45 2018
@@ -1708,10 +1708,15 @@ Instruction *InstCombiner::visitFSub(Bin
       if (Instruction *NV = FoldOpIntoSelect(I, SI))
         return NV;
 
-  // If this is a 'B = x-(-A)', change to B = x+A, potentially looking
-  // through FP extensions/truncations along the way.
-  if (Value *V = dyn_castFNegVal(Op1))
-    return BinaryOperator::CreateFAddFMF(Op0, V, &I);
+  // X - C --> X + (-C)
+  Constant *C;
+  if (match(Op1, m_Constant(C)))
+    return BinaryOperator::CreateFAddFMF(Op0, ConstantExpr::getFNeg(C), &I);
+  
+  // X - (-Y) --> X + Y
+  Value *Y;
+  if (match(Op1, m_FNeg(m_Value(Y))))
+    return BinaryOperator::CreateFAddFMF(Op0, Y, &I);
 
   if (FPTruncInst *FPTI = dyn_cast<FPTruncInst>(Op1)) {
     if (Value *V = dyn_castFNegVal(FPTI->getOperand(0))) {

Modified: llvm/trunk/test/Transforms/InstCombine/fsub.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/fsub.ll?rev=329316&r1=329315&r2=329316&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/fsub.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/fsub.ll Thu Apr  5 10:06:45 2018
@@ -49,7 +49,7 @@ define <2 x float> @constant_op1_vec(<2
 
 define <2 x float> @constant_op1_vec_undef(<2 x float> %x, <2 x float> %y) {
 ; CHECK-LABEL: @constant_op1_vec_undef(
-; CHECK-NEXT:    [[R:%.*]] = fsub <2 x float> [[X:%.*]], <float undef, float -4.200000e+01>
+; CHECK-NEXT:    [[R:%.*]] = fadd <2 x float> [[X:%.*]], <float 0x7FF8000000000000, float 4.200000e+01>
 ; CHECK-NEXT:    ret <2 x float> [[R]]
 ;
   %r = fsub <2 x float> %x, <float undef, float -42.0>
@@ -80,8 +80,7 @@ define <2 x float> @neg_op1_vec(<2 x flo
 
 define <2 x float> @neg_op1_vec_undef(<2 x float> %x, <2 x float> %y) {
 ; CHECK-LABEL: @neg_op1_vec_undef(
-; CHECK-NEXT:    [[NEGY:%.*]] = fsub <2 x float> <float -0.000000e+00, float undef>, [[Y:%.*]]
-; CHECK-NEXT:    [[R:%.*]] = fsub <2 x float> [[X:%.*]], [[NEGY]]
+; CHECK-NEXT:    [[R:%.*]] = fadd <2 x float> [[X:%.*]], [[Y:%.*]]
 ; CHECK-NEXT:    ret <2 x float> [[R]]
 ;
   %negy = fsub <2 x float> <float -0.0, float undef>, %y