[llvm-commits] CVS: llvm/lib/Transforms/IPO/GlobalOpt.cpp
Chris Lattner
lattner at cs.uiuc.edu
Fri Oct 8 13:59:39 PDT 2004
Changes in directory llvm/lib/Transforms/IPO:
GlobalOpt.cpp updated: 1.14 -> 1.15
---
Log message:
* Pull out the meat of runOnModule into another function for clarity.
* Do not lead dangling dead constants prevent optimization
* Iterate global optimization while we're making progress.
These changes allow us to be more aggressive, handling cases like
GlobalOpt/iterate.llx without a problem (turning it into 'ret int 0').
---
Diffs of the changes: (+101 -45)
Index: llvm/lib/Transforms/IPO/GlobalOpt.cpp
diff -u llvm/lib/Transforms/IPO/GlobalOpt.cpp:1.14 llvm/lib/Transforms/IPO/GlobalOpt.cpp:1.15
--- llvm/lib/Transforms/IPO/GlobalOpt.cpp:1.14 Fri Oct 8 15:25:55 2004
+++ llvm/lib/Transforms/IPO/GlobalOpt.cpp Fri Oct 8 15:59:28 2004
@@ -87,6 +87,24 @@
isNotSuitableForSRA(false) {}
};
+
+
+/// ConstantIsDead - Return true if the specified constant is (transitively)
+/// dead. The constant may be used by other constants (e.g. constant arrays and
+/// constant exprs) as long as they are dead, but it cannot be used by anything
+/// else.
+static bool ConstantIsDead(Constant *C) {
+ if (isa<GlobalValue>(C)) return false;
+
+ for (Value::use_iterator UI = C->use_begin(), E = C->use_end(); UI != E; ++UI)
+ if (Constant *CU = dyn_cast<Constant>(*UI)) {
+ if (!ConstantIsDead(CU)) return false;
+ } else
+ return false;
+ return true;
+}
+
+
/// AnalyzeGlobal - Look at all uses of the global and fill in the GlobalStatus
/// structure. If the global has its address taken, return true to indicate we
/// can't do anything with it.
@@ -160,6 +178,10 @@
} else {
return true; // Any other non-load instruction might take address!
}
+ } else if (Constant *C = dyn_cast<Constant>(*UI)) {
+ // We might have a dead and dangling constant hanging off of here.
+ if (!ConstantIsDead(C))
+ return true;
} else {
// Otherwise must be a global or some other user.
return true;
@@ -232,6 +254,15 @@
CleanupConstantGlobalUsers(GEP, SubInit);
if (GEP->use_empty())
GEP->getParent()->getInstList().erase(GEP);
+ } else if (Constant *C = dyn_cast<Constant>(U)) {
+ // If we have a chain of dead constantexprs or other things dangling from
+ // us, and if they are all dead, nuke them without remorse.
+ if (ConstantIsDead(C)) {
+ C->destroyConstant();
+ // This could have incalidated UI, start over from scratch.x
+ CleanupConstantGlobalUsers(V, Init);
+ return;
+ }
}
}
}
@@ -322,6 +353,67 @@
return NewGlobals[0];
}
+
+/// ProcessInternalGlobal - Analyze the specified global variable and optimize
+/// it if possible. If we make a change, return true.
+static bool ProcessInternalGlobal(GlobalVariable *GV, Module::giterator &GVI) {
+ std::set<PHINode*> PHIUsers;
+ GlobalStatus GS;
+ PHIUsers.clear();
+ GV->removeDeadConstantUsers();
+
+ if (GV->use_empty()) {
+ DEBUG(std::cerr << "GLOBAL DEAD: " << *GV);
+ ++NumDeleted;
+ return true;
+ }
+
+ if (!AnalyzeGlobal(GV, GS, PHIUsers)) {
+ // If the global is never loaded (but may be stored to), it is dead.
+ // Delete it now.
+ if (!GS.isLoaded) {
+ DEBUG(std::cerr << "GLOBAL NEVER LOADED: " << *GV);
+ // Delete any stores we can find to the global. We may not be able to
+ // make it completely dead though.
+ CleanupConstantGlobalUsers(GV, GV->getInitializer());
+
+ // If the global is dead now, delete it.
+ if (GV->use_empty()) {
+ GV->getParent()->getGlobalList().erase(GV);
+ ++NumDeleted;
+ }
+ return true;
+
+ } else if (GS.StoredType <= GlobalStatus::isInitializerStored) {
+ DEBUG(std::cerr << "MARKING CONSTANT: " << *GV);
+ GV->setConstant(true);
+
+ // Clean up any obviously simplifiable users now.
+ CleanupConstantGlobalUsers(GV, GV->getInitializer());
+
+ // If the global is dead now, just nuke it.
+ if (GV->use_empty()) {
+ DEBUG(std::cerr << " *** Marking constant allowed us to simplify "
+ "all users and delete global!\n");
+ GV->getParent()->getGlobalList().erase(GV);
+ ++NumDeleted;
+ }
+
+ ++NumMarked;
+ return true;
+ } else if (!GS.isNotSuitableForSRA &&
+ !GV->getInitializer()->getType()->isFirstClassType()) {
+ DEBUG(std::cerr << "PERFORMING GLOBAL SRA ON: " << *GV);
+ if (GlobalVariable *FirstNewGV = SRAGlobal(GV)) {
+ GVI = FirstNewGV; // Don't skip the newly produced globals!
+ return true;
+ }
+ }
+ }
+ return false;
+}
+
+
bool GlobalOpt::runOnModule(Module &M) {
bool Changed = false;
@@ -341,52 +433,16 @@
Changed |= LocalChange;
}
- std::set<PHINode*> PHIUsers;
- for (Module::giterator GVI = M.gbegin(), E = M.gend(); GVI != E;) {
- GlobalVariable *GV = GVI++;
- if (!GV->isConstant() && GV->hasInternalLinkage() && GV->hasInitializer()) {
- GlobalStatus GS;
- PHIUsers.clear();
- GV->removeDeadConstantUsers();
- if (!AnalyzeGlobal(GV, GS, PHIUsers)) {
- // If the global is never loaded (but may be stored to), it is dead.
- // Delete it now.
- if (!GS.isLoaded) {
- DEBUG(std::cerr << "GLOBAL NEVER LOADED: " << *GV);
- // Delete any stores we can find to the global. We may not be able to
- // make it completely dead though.
- CleanupConstantGlobalUsers(GV, GV->getInitializer());
-
- // If the global is dead now, delete it.
- if (GV->use_empty()) {
- M.getGlobalList().erase(GV);
- ++NumDeleted;
- }
- Changed = true;
-
- } else if (GS.StoredType <= GlobalStatus::isInitializerStored) {
- DEBUG(std::cerr << "MARKING CONSTANT: " << *GV);
- GV->setConstant(true);
-
- // Clean up any obviously simplifiable users now.
- CleanupConstantGlobalUsers(GV, GV->getInitializer());
-
- // If the global is dead now, just nuke it.
- if (GV->use_empty()) {
- M.getGlobalList().erase(GV);
- ++NumDeleted;
- }
-
- ++NumMarked;
- Changed = true;
- } else if (!GS.isNotSuitableForSRA &&
- !GV->getInitializer()->getType()->isFirstClassType()) {
- DEBUG(std::cerr << "PERFORMING GLOBAL SRA ON: " << *GV);
- if (GlobalVariable *FirstNewGV = SRAGlobal(GV))
- GVI = FirstNewGV; // Don't skip the newly produced globals!
- }
- }
+ LocalChange = true;
+ while (LocalChange) {
+ LocalChange = false;
+ for (Module::giterator GVI = M.gbegin(), E = M.gend(); GVI != E;) {
+ GlobalVariable *GV = GVI++;
+ if (!GV->isConstant() && GV->hasInternalLinkage() &&
+ GV->hasInitializer())
+ LocalChange |= ProcessInternalGlobal(GV, GVI);
}
+ Changed |= LocalChange;
}
return Changed;
}
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