[CorrelatedValuePropagation] Remove redundant if statement in processSelect()

[Enna1]

Summary

[CorrelatedValuePropagation] Remove redundant if statement in processSelect()

This statement if (ReplaceWith == S) ReplaceWith = UndefValue::get(S->getType()); is introduced in "https://reviews.llvm.org/rG35609d97ae89b8e13f40f4e6b9b056954f8baa83" to fix a case where unreachable code can cause select instruction simplification to fail.
In "https://reviews.llvm.org/rGd10480657527ffb44ea213460fb3676a6b1300aa", we begin to perform a depth-first walk of basic blocks. This means we will not visit unreachable blocks.
So we do not need this the special check any more.

[nikic]

LGTM

llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp

139

Not really related to your change, but the use of swap here is pretty awkward, I'd write this as Value *ReplaceWith = CI->isOne() ? S->getTrueValue() : S->getFalseValue().

[Enna1]

update code as suggestion

[Enna1]

Cause I don't have commit access, can you help me to commit this patch ?
Thanks!

llvm/lib/Transforms/Scalar/CorrelatedValuePropagation.cpp

 
 // Public interface to the Value Propagation pass
 Pass *llvm::createCorrelatedValuePropagationPass() {
   return new CorrelatedValuePropagation();
 }
 
 static bool processSelect(SelectInst *S, LazyValueInfo *LVI) {
   if (S->getType()->isVectorTy()) return false;
-  if (isa<Constant>(S->getOperand(0))) return false;
+  if (isa<Constant>(S->getCondition())) return false;
 
   Constant *C = LVI->getConstant(S->getCondition(), S->getParent(), S);
   if (!C) return false;
 
   ConstantInt *CI = dyn_cast<ConstantInt>(C);
   if (!CI) return false;
 
   Value *ReplaceWith = S->getTrueValue();
   Value *Other = S->getFalseValue();
   if (!CI->isOne()) std::swap(ReplaceWith, Other);
-  if (ReplaceWith == S) ReplaceWith = UndefValue::get(S->getType());
 
   S->replaceAllUsesWith(ReplaceWith);
   S->eraseFromParent();
 
   ++NumSelects;
 
   return true;
 }