[InstCombine] Enable Add/Sub simplifications with only 'reassoc' FMF

These simplifications were previously enabled only with isFast(), but that
is more restrictive than required. Since r317488, FMF has 'reassoc' to
control these cases at a finer level.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@330089 91177308-0d34-0410-b5e6-96231b3b80d8

Author: wjristow

lib/Transforms/InstCombine/InstCombineAddSub.cpp

@@ -511,7 +511,8 @@ Value *FAddCombine::performFactorization(Instruction *I) {
 }
 
 Value *FAddCombine::simplify(Instruction *I) {
-  assert(I->isFast() && "Expected 'fast' instruction");
+  assert(I->hasAllowReassoc() && I->hasNoSignedZeros() &&
+         "Expected 'reassoc'+'nsz' instruction");
 
   // Currently we are not able to handle vector type.
   if (I->getType()->isVectorTy())
@@ -1378,7 +1379,7 @@ Instruction *InstCombiner::visitFAdd(BinaryOperator &I) {
   if (Value *V = SimplifySelectsFeedingBinaryOp(I, LHS, RHS))
     return replaceInstUsesWith(I, V);
 
-  if (I.isFast()) {
+  if (I.hasAllowReassoc() && I.hasNoSignedZeros()) {
     if (Value *V = FAddCombine(Builder).simplify(&I))
       return replaceInstUsesWith(I, V);
   }
@@ -1747,7 +1748,7 @@ Instruction *InstCombiner::visitFSub(BinaryOperator &I) {
   if (Value *V = SimplifySelectsFeedingBinaryOp(I, Op0, Op1))
     return replaceInstUsesWith(I, V);
 
-  if (I.isFast()) {
+  if (I.hasAllowReassoc() && I.hasNoSignedZeros()) {
     if (Value *V = FAddCombine(Builder).simplify(&I))
       return replaceInstUsesWith(I, V);
   }