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Promote getelementptr instructions to constexprs if we can.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@3368 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2002-08-17 22:21:59 +00:00
parent e4619181cc
commit 9b76123124
1 changed files with 19 additions and 3 deletions
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22
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -540,7 +540,6 @@ static inline bool isEliminableCastOfCast(const CastInst &CI,
return SrcSize != MidSize || SrcTy == Type::BoolTy;
default: assert(0 && "Bad entry in sign table!");
}
return false; // NOT REACHED
}
}
@ -614,8 +613,7 @@ Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
// is a getelementptr instruction, combine the indices of the two
// getelementptr instructions into a single instruction.
//
if (GetElementPtrInst *Src =
dyn_cast<GetElementPtrInst>(GEP.getPointerOperand())) {
if (GetElementPtrInst *Src = dyn_cast<GetElementPtrInst>(GEP.getOperand(0))) {
std::vector<Value *> Indices;
// Can we combine the two pointer arithmetics offsets?
@ -635,6 +633,24 @@ Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
if (!Indices.empty())
return new GetElementPtrInst(Src->getOperand(0), Indices, GEP.getName());
} else if (GlobalValue *GV = dyn_cast<GlobalValue>(GEP.getOperand(0))) {
// GEP of global variable. If all of the indices for this GEP are
// constants, we can promote this to a constexpr instead of an instruction.
// Scan for nonconstants...
std::vector<Constant*> Indices;
User::op_iterator I = GEP.idx_begin(), E = GEP.idx_end();
for (; I != E && isa<Constant>(*I); ++I)
Indices.push_back(cast<Constant>(*I));
if (I == E) { // If they are all constants...
ConstantExpr *CE =
ConstantExpr::getGetElementPtr(ConstantPointerRef::get(GV), Indices);
// Replace all uses of the GEP with the new constexpr...
return ReplaceInstUsesWith(GEP, CE);
}
}
return 0;