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Implement test/Regression/Transforms/GlobalConstifier/phi-select.llx

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This allows more globals to be marked constant, particularly global arrays.

llvm-svn: 15735
This commit is contained in:
Chris Lattner 2004-08-14 20:57:17 +00:00
parent f155b56d41
commit 8e2dc1a98a
1 changed files with 16 additions and 6 deletions
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22
lib/Transforms/IPO/GlobalConstifier.cpp
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@ -25,6 +25,7 @@
#include "llvm/Pass.h"
#include "Support/Debug.h"
#include "Support/Statistic.h"
#include <set>
using namespace llvm;
namespace {
@ -52,16 +53,23 @@ static bool ContainingFunctionIsTriviallyDead(Instruction *I) {
/// isStoredThrough - Return false if the specified pointer is provably never
/// stored through. If we can't tell, we must conservatively assume it might.
///
static bool isStoredThrough(Value *V) {
static bool isStoredThrough(Value *V, std::set<PHINode*> &PHIUsers) {
for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI)
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(*UI)) {
if (isStoredThrough(CE))
if (isStoredThrough(CE, PHIUsers))
return true;
} else if (Instruction *I = dyn_cast<Instruction>(*UI)) {
if (!ContainingFunctionIsTriviallyDead(I)) {
if (I->getOpcode() == Instruction::GetElementPtr) {
if (isStoredThrough(I)) return true;
} else if (!isa<LoadInst>(*UI) && !isa<SetCondInst>(*UI)) {
if (I->getOpcode() == Instruction::GetElementPtr ||
I->getOpcode() == Instruction::Select) {
if (isStoredThrough(I, PHIUsers)) return true;
} else if (PHINode *PN = dyn_cast<PHINode>(I)) {
// PHI nodes we can check just like select or GEP instructions, but we
// have to be careful about infinite recursion.
if (PHIUsers.insert(PN).second) // Not already visited.
if (isStoredThrough(I, PHIUsers)) return true;
} else if (!isa<LoadInst>(I) && !isa<SetCondInst>(I)) {
return true; // Any other non-load instruction might store!
}
}
@ -75,14 +83,16 @@ static bool isStoredThrough(Value *V) {
bool Constifier::run(Module &M) {
bool Changed = false;
std::set<PHINode*> PHIUsers;
for (Module::giterator GV = M.gbegin(), E = M.gend(); GV != E; ++GV)
if (!GV->isConstant() && GV->hasInternalLinkage() && GV->hasInitializer()) {
if (!isStoredThrough(GV)) {
if (!isStoredThrough(GV, PHIUsers)) {
DEBUG(std::cerr << "MARKING CONSTANT: " << *GV << "\n");
GV->setConstant(true);
++NumMarked;
Changed = true;
}
PHIUsers.clear();
}
return Changed;
}