maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity

Improve comments, no functionality changes 

llvm-svn: 16814
This commit is contained in:
Chris Lattner 2004-10-07 21:30:30 +00:00
parent 3ae7bb6b7c
commit 617f1a34f1
1 changed files with 53 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

71
llvm/lib/Transforms/IPO/GlobalOpt.cpp
View File

@ -42,15 +42,45 @@ ModulePass *llvm::createGlobalOptimizerPass() { return new GlobalOpt(); }
/// GlobalStatus - As we analyze each global, keep track of some information
/// about it. If we find out that the address of the global is taken, none of
/// the other info will be accurate.
/// this info will be accurate.
struct GlobalStatus {
/// isLoaded - True if the global is ever loaded. If the global isn't ever
/// loaded it can be deleted.
bool isLoaded;
/// StoredType - Keep track of what stores to the global look like.
///
enum StoredType {
NotStored, isInitializerStored, isMallocStored, isStored
/// NotStored - There is no store to this global. It can thus be marked
/// constant.
NotStored,
/// isInitializerStored - This global is stored to, but the only thing
/// stored is the constant it was initialized with. This is only tracked
/// for scalar globals.
isInitializerStored,
/// isStoredOnce - This global is stored to, but only its initializer and
/// one other value is ever stored to it. If this global isStoredOnce, we
/// track the value stored to it in StoredOnceValue below. This is only
/// tracked for scalar globals.
isStoredOnce,
/// isStored - This global is stored to by multiple values or something else
/// that we cannot track.
isStored
} StoredType;
/// StoredOnceValue - If only one value (besides the initializer constant) is
/// ever stored to this global, keep track of what value it is.
Value *StoredOnceValue;
/// isNotSuitableForSRA - Keep track of whether any SRA preventing users of
/// the global exist. Such users include GEP instruction with variable
/// indexes, and non-gep/load/store users like constant expr casts.
bool isNotSuitableForSRA;
GlobalStatus() : isLoaded(false), StoredType(NotStored),
GlobalStatus() : isLoaded(false), StoredType(NotStored), StoredOnceValue(0),
isNotSuitableForSRA(false) {}
};
@ -72,24 +102,29 @@ static bool AnalyzeGlobal(Value *V, GlobalStatus &GS,
// Don't allow a store OF the address, only stores TO the address.
if (SI->getOperand(0) == V) return true;
// If this store is just storing the initializer into a global (i.e. not
// changing the value), ignore it. For now we just handle direct
// stores, no stores to fields of aggregates.
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(SI->getOperand(1))) {
if (SI->getOperand(0) == GV->getInitializer() &&
GS.StoredType < GlobalStatus::isInitializerStored)
GS.StoredType = GlobalStatus::isInitializerStored;
else if (isa<MallocInst>(SI->getOperand(0)) &&
GS.StoredType < GlobalStatus::isMallocStored)
GS.StoredType = GlobalStatus::isMallocStored;
else
// If this is a direct store to the global (i.e., the global is a scalar
// value, not an aggregate), keep more specific information about
// stores.
if (GS.StoredType != GlobalStatus::isStored)
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(SI->getOperand(1))){
if (SI->getOperand(0) == GV->getInitializer()) {
if (GS.StoredType < GlobalStatus::isInitializerStored)
GS.StoredType = GlobalStatus::isInitializerStored;
} else if (GS.StoredType < GlobalStatus::isStoredOnce) {
GS.StoredType = GlobalStatus::isStoredOnce;
GS.StoredOnceValue = SI->getOperand(0);
} else if (GS.StoredType == GlobalStatus::isStoredOnce &&
GS.StoredOnceValue == SI->getOperand(0)) {
// noop.
} else {
GS.StoredType = GlobalStatus::isStored;
}
} else {
GS.StoredType = GlobalStatus::isStored;
} else {
GS.StoredType = GlobalStatus::isStored;
}
}
} else if (I->getOpcode() == Instruction::GetElementPtr) {
if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
if (!GS.isNotSuitableForSRA)
if (!GS.isNotSuitableForSRA)// Check to see if we have any variable idxs
for (unsigned i = 1, e = I->getNumOperands(); i != e; ++i)
if (!isa<Constant>(I->getOperand(i))) {
GS.isNotSuitableForSRA = true;