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llvm-mirror/lib/Transforms/Scalar/ConstantProp.cpp
Chandler Carruth eb66b33867 Sort the remaining #include lines in include/... and lib/....
I did this a long time ago with a janky python script, but now
clang-format has built-in support for this. I fed clang-format every
line with a #include and let it re-sort things according to the precise
LLVM rules for include ordering baked into clang-format these days.

I've reverted a number of files where the results of sorting includes
isn't healthy. Either places where we have legacy code relying on
particular include ordering (where possible, I'll fix these separately)
or where we have particular formatting around #include lines that
I didn't want to disturb in this patch.

This patch is *entirely* mechanical. If you get merge conflicts or
anything, just ignore the changes in this patch and run clang-format
over your #include lines in the files.

Sorry for any noise here, but it is important to keep these things
stable. I was seeing an increasing number of patches with irrelevant
re-ordering of #include lines because clang-format was used. This patch
at least isolates that churn, makes it easy to skip when resolving
conflicts, and gets us to a clean baseline (again).

llvm-svn: 304787
2017-06-06 11:49:48 +00:00

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/ADT/Statistic.h"
#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/IR/Constant.h"
#include "llvm/IR/InstIterator.h"
#include "llvm/IR/Instruction.h"
#include "llvm/Pass.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Utils/Local.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;
}