mirror of
https://github.com/RPCS3/llvm-mirror.git
synced 2024-10-23 21:13:02 +02:00
d65fa7c292
Just because we can constant fold the result of an instruction does not imply that we can delete the instruction. It may have side effects. This fixes PR28655. llvm-svn: 276389
105 lines
3.3 KiB
C++
105 lines
3.3 KiB
C++
//===- ConstantProp.cpp - Code to perform Simple Constant Propagation -----===//
|
|
//
|
|
// The LLVM Compiler Infrastructure
|
|
//
|
|
// This file is distributed under the University of Illinois Open Source
|
|
// License. See LICENSE.TXT for details.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
// This file implements constant propagation and merging:
|
|
//
|
|
// Specifically, this:
|
|
// * Converts instructions like "add int 1, 2" into 3
|
|
//
|
|
// Notice that:
|
|
// * This pass has a habit of making definitions be dead. It is a good idea
|
|
// to run a DIE pass sometime after running this pass.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#include "llvm/Transforms/Scalar.h"
|
|
#include "llvm/Transforms/Utils/Local.h"
|
|
#include "llvm/ADT/Statistic.h"
|
|
#include "llvm/Analysis/ConstantFolding.h"
|
|
#include "llvm/IR/Constant.h"
|
|
#include "llvm/IR/InstIterator.h"
|
|
#include "llvm/IR/Instruction.h"
|
|
#include "llvm/Pass.h"
|
|
#include "llvm/Analysis/TargetLibraryInfo.h"
|
|
#include <set>
|
|
using namespace llvm;
|
|
|
|
#define DEBUG_TYPE "constprop"
|
|
|
|
STATISTIC(NumInstKilled, "Number of instructions killed");
|
|
|
|
namespace {
|
|
struct ConstantPropagation : public FunctionPass {
|
|
static char ID; // Pass identification, replacement for typeid
|
|
ConstantPropagation() : FunctionPass(ID) {
|
|
initializeConstantPropagationPass(*PassRegistry::getPassRegistry());
|
|
}
|
|
|
|
bool runOnFunction(Function &F) override;
|
|
|
|
void getAnalysisUsage(AnalysisUsage &AU) const override {
|
|
AU.setPreservesCFG();
|
|
AU.addRequired<TargetLibraryInfoWrapperPass>();
|
|
}
|
|
};
|
|
}
|
|
|
|
char ConstantPropagation::ID = 0;
|
|
INITIALIZE_PASS_BEGIN(ConstantPropagation, "constprop",
|
|
"Simple constant propagation", false, false)
|
|
INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
|
|
INITIALIZE_PASS_END(ConstantPropagation, "constprop",
|
|
"Simple constant propagation", false, false)
|
|
|
|
FunctionPass *llvm::createConstantPropagationPass() {
|
|
return new ConstantPropagation();
|
|
}
|
|
|
|
bool ConstantPropagation::runOnFunction(Function &F) {
|
|
if (skipFunction(F))
|
|
return false;
|
|
|
|
// Initialize the worklist to all of the instructions ready to process...
|
|
std::set<Instruction*> WorkList;
|
|
for (Instruction &I: instructions(&F))
|
|
WorkList.insert(&I);
|
|
|
|
bool Changed = false;
|
|
const DataLayout &DL = F.getParent()->getDataLayout();
|
|
TargetLibraryInfo *TLI =
|
|
&getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
|
|
|
|
while (!WorkList.empty()) {
|
|
Instruction *I = *WorkList.begin();
|
|
WorkList.erase(WorkList.begin()); // Get an element from the worklist...
|
|
|
|
if (!I->use_empty()) // Don't muck with dead instructions...
|
|
if (Constant *C = ConstantFoldInstruction(I, DL, TLI)) {
|
|
// Add all of the users of this instruction to the worklist, they might
|
|
// be constant propagatable now...
|
|
for (User *U : I->users())
|
|
WorkList.insert(cast<Instruction>(U));
|
|
|
|
// Replace all of the uses of a variable with uses of the constant.
|
|
I->replaceAllUsesWith(C);
|
|
|
|
// Remove the dead instruction.
|
|
WorkList.erase(I);
|
|
if (isInstructionTriviallyDead(I, TLI)) {
|
|
I->eraseFromParent();
|
|
++NumInstKilled;
|
|
}
|
|
|
|
// We made a change to the function...
|
|
Changed = true;
|
|
}
|
|
}
|
|
return Changed;
|
|
}
|