6502/llvm-6502
1
0
Fork 0
mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2025-01-01 00:33:09 +00:00
Code Issues Projects Releases Wiki Activity

- Dramatically simplify the ConstantMerge code now that

Browse Source 
Value::replaceAllUsesWith works with constants correctly.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@4104 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2002-10-09 23:16:04 +00:00
parent 28eca8bb56
commit c67ebfa788
1 changed files with 3 additions and 102 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

105
lib/Transforms/IPO/ConstantMerge.cpp
View File

@ -12,23 +12,19 @@
#include "llvm/Transforms/IPO.h"
#include "llvm/Module.h"
#include "llvm/Constants.h"
#include "llvm/Pass.h"
#include "Support/Statistic.h"
namespace {
Statistic<> NumMerged("constmerge", "Number of global constants merged");
struct ConstantMerge : public Pass {
// run - For this pass, process all of the globals in the module,
// eliminating duplicate constants.
//
bool run(Module &M);
private:
void replaceUsesOfWith(GlobalVariable *Old, GlobalVariable *New);
void replaceConstantWith(Constant *Old, Constant *New);
};
Statistic<> NumMerged("constmerge", "Number of global constants merged");
RegisterOpt<ConstantMerge> X("constmerge","Merge Duplicate Global Constants");
}
@ -51,7 +47,7 @@ bool ConstantMerge::run(Module &M) {
CMap.insert(I, std::make_pair(Init, GV));
} else { // Yup, this is a duplicate!
// Make all uses of the duplicate constant use the cannonical version...
replaceUsesOfWith(GV, I->second);
GV->replaceAllUsesWith(I->second);
// Delete the global value from the module... and back up iterator to
// not skip the next global...
@ -64,98 +60,3 @@ bool ConstantMerge::run(Module &M) {
return MadeChanges;
}
/// replaceUsesOfWith - Replace all uses of Old with New. For instructions,
/// this is a really simple matter of replacing the reference to Old with a
/// reference to New. For constants references, however, we must carefully
/// build replacement constants to substitute in.
///
void ConstantMerge::replaceUsesOfWith(GlobalVariable *Old, GlobalVariable *New){
while (!Old->use_empty()) {
User *U = Old->use_back();
if (ConstantPointerRef *CPR = dyn_cast<ConstantPointerRef>(U))
replaceConstantWith(CPR, ConstantPointerRef::get(New));
else
U->replaceUsesOfWith(Old, New);
}
}
/// replaceWith - Ok, so we have a constant 'Old' and we want to replace it with
/// 'New'. To do this, we have to recursively go through the uses of Old,
/// replacing them with new things. The problem is that if a constant uses Old,
/// then we need to replace the uses of the constant with uses of the equivalent
/// constant that uses New instead.
///
void ConstantMerge::replaceConstantWith(Constant *Old, Constant *New) {
while (!Old->use_empty()) {
User *U = Old->use_back();
if (Constant *C = dyn_cast<Constant>(U)) {
Constant *Replacement = 0;
// Depending on the type of constant, build a suitable replacement...
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) {
if (CE->getOpcode() == Instruction::GetElementPtr) {
std::vector<Constant*> Indices;
Constant *Pointer = cast<Constant>(CE->getOperand(0));
Indices.reserve(CE->getNumOperands()-1);
if (Pointer == Old) Pointer = New;
for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i) {
Constant *Val = cast<Constant>(CE->getOperand(i));
if (Val == Old) Val = New;
Indices.push_back(Val);
}
Replacement = ConstantExpr::getGetElementPtr(Pointer, Indices);
} else if (CE->getOpcode() == Instruction::Cast) {
assert(CE->getOperand(0) == Old && "Cast only has one use!");
Replacement = ConstantExpr::getCast(New, CE->getType());
} else if (CE->getNumOperands() == 2) {
Constant *C1 = cast<Constant>(CE->getOperand(0));
Constant *C2 = cast<Constant>(CE->getOperand(1));
if (C1 == Old) C1 = New;
if (C2 == Old) C2 = New;
Replacement = ConstantExpr::get(CE->getOpcode(), C1, C2);
} else {
assert(0 && "Unknown ConstantExpr type!");
}
} else if (ConstantArray *CA = dyn_cast<ConstantArray>(C)) {
std::vector<Constant*> Values;
Values.reserve(CA->getValues().size());
for (unsigned i = 0, e = CA->getValues().size(); i != e; ++i) {
Constant *Val = cast<Constant>(CA->getValues()[i]);
if (Val == Old) Val = New;
Values.push_back(Val);
}
Replacement = ConstantArray::get(CA->getType(), Values);
} else if (ConstantStruct *CS = dyn_cast<ConstantStruct>(C)) {
std::vector<Constant*> Values;
Values.reserve(CS->getValues().size());
for (unsigned i = 0, e = CS->getValues().size(); i != e; ++i) {
Constant *Val = cast<Constant>(CS->getValues()[i]);
if (Val == Old) Val = New;
Values.push_back(Val);
}
Replacement = ConstantStruct::get(CS->getType(), Values);
} else {
assert(0 && "Unexpected/unknown constant type!");
}
// Now that we have a suitable replacement, recursively eliminate C.
replaceConstantWith(C, Replacement);
} else {
// If it is not a constant, we can simply replace uses of Old with New.
U->replaceUsesOfWith(Old, New);
}
}
// No-one refers to this old dead constant now, destroy it!
Old->destroyConstant();
}