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Add constant prop & DIE to InstCombine, so it cleans up after itself

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@3568 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2002-09-02 04:59:56 +00:00
parent b041eb5dd4
commit 62b14df410
1 changed files with 45 additions and 9 deletions
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54
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -1,9 +1,8 @@
//===- InstructionCombining.cpp - Combine multiple instructions -----------===//
//
// InstructionCombining - Combine instructions to form fewer, simple
// instructions. This pass does not modify the CFG, and has a tendancy to
// make instructions dead, so a subsequent DIE pass is useful. This pass is
// where algebraic simplification happens.
// instructions. This pass does not modify the CFG This pass is where algebraic
// simplification happens.
//
// This pass combines things like:
// %Y = add int 1, %X
@ -29,7 +28,9 @@
#include "Support/StatisticReporter.h"
#include <algorithm>
static Statistic<> NumCombined("instcombine\t- Number of insts combined");
static Statistic<> NumCombined ("instcombine\t- Number of insts combined");
static Statistic<> NumConstProp("instcombine\t- Number of constant folds");
static Statistic<> NumDeadInst ("instcombine\t- Number of dead inst eliminate");
namespace {
class InstCombiner : public FunctionPass,
@ -46,6 +47,8 @@ namespace {
WorkList.push_back(cast<Instruction>(*UI));
}
// removeFromWorkList - remove all instances of I from the worklist.
void removeFromWorkList(Instruction *I);
public:
virtual bool runOnFunction(Function &F);
@ -697,6 +700,11 @@ Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
}
void InstCombiner::removeFromWorkList(Instruction *I) {
WorkList.erase(std::remove(WorkList.begin(), WorkList.end(), I),
WorkList.end());
}
bool InstCombiner::runOnFunction(Function &F) {
bool Changed = false;
@ -706,6 +714,37 @@ bool InstCombiner::runOnFunction(Function &F) {
Instruction *I = WorkList.back(); // Get an instruction from the worklist
WorkList.pop_back();
// Check to see if we can DCE or ConstantPropogate the instruction...
// Check to see if we can DIE the instruction...
if (isInstructionTriviallyDead(I)) {
// Add operands to the worklist...
for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
if (Instruction *Op = dyn_cast<Instruction>(I->getOperand(i)))
WorkList.push_back(Op);
++NumDeadInst;
BasicBlock::iterator BBI = I;
if (dceInstruction(BBI)) {
removeFromWorkList(I);
continue;
}
}
// Instruction isn't dead, see if we can constant propogate it...
if (Constant *C = ConstantFoldInstruction(I)) {
// Add operands to the worklist...
for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
if (Instruction *Op = dyn_cast<Instruction>(I->getOperand(i)))
WorkList.push_back(Op);
I->replaceAllUsesWith(C);
++NumConstProp;
BasicBlock::iterator BBI = I;
if (dceInstruction(BBI)) {
removeFromWorkList(I);
continue;
}
}
// Now that we have an instruction, try combining it to simplify it...
if (Instruction *Result = visit(*I)) {
++NumCombined;
@ -713,9 +752,7 @@ bool InstCombiner::runOnFunction(Function &F) {
if (Result != I) {
// Instructions can end up on the worklist more than once. Make sure
// we do not process an instruction that has been deleted.
WorkList.erase(std::remove(WorkList.begin(), WorkList.end(), I),
WorkList.end());
removeFromWorkList(I);
ReplaceInstWithInst(I, Result);
} else {
BasicBlock::iterator II = I;
@ -725,8 +762,7 @@ bool InstCombiner::runOnFunction(Function &F) {
if (dceInstruction(II)) {
// Instructions may end up in the worklist more than once. Erase them
// all.
WorkList.erase(std::remove(WorkList.begin(), WorkList.end(), I),
WorkList.end());
removeFromWorkList(I);
Result = 0;
}
}