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remove doConstantPropagation and dceInstruction, they are just

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wrappers around the interesting code and use an obscure iterator
abstraction that dates back many many years.

Move EraseDeadInstructions to Transforms/Utils and name it
RecursivelyDeleteTriviallyDeadInstructions.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60191 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner
2008-11-27 22:57:53 +00:00
parent 15678533f3
commit 3481f24c06
3 changed files with 34 additions and 66 deletions
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55
lib/Transforms/Utils/Local.cpp
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@@ -22,30 +22,13 @@
#include "llvm/Target/TargetData.h"
#include "llvm/Support/GetElementPtrTypeIterator.h"
#include "llvm/Support/MathExtras.h"
#include <cerrno>
#include "llvm/ADT/SmallPtrSet.h"
using namespace llvm;
//===----------------------------------------------------------------------===//
// Local constant propagation...
// Local constant propagation.
//
/// doConstantPropagation - If an instruction references constants, try to fold
/// them together...
///
bool llvm::doConstantPropagation(BasicBlock::iterator &II,
const TargetData *TD) {
if (Constant *C = ConstantFoldInstruction(II, TD)) {
// Replaces all of the uses of a variable with uses of the constant.
II->replaceAllUsesWith(C);
// Remove the instruction from the basic block...
II = II->getParent()->getInstList().erase(II);
return true;
}
return false;
}
// ConstantFoldTerminator - If a terminator instruction is predicated on a
// constant value, convert it into an unconditional branch to the constant
// destination.
@@ -171,6 +154,9 @@ bool llvm::ConstantFoldTerminator(BasicBlock *BB) {
// Local dead code elimination...
//
/// isInstructionTriviallyDead - Return true if the result produced by the
/// instruction is not used, and the instruction has no side effects.
///
bool llvm::isInstructionTriviallyDead(Instruction *I) {
if (!I->use_empty() || isa<TerminatorInst>(I)) return false;
@@ -187,20 +173,29 @@ bool llvm::isInstructionTriviallyDead(Instruction *I) {
return false;
}
// dceInstruction - Inspect the instruction at *BBI and figure out if it's
// [trivially] dead. If so, remove the instruction and update the iterator
// to point to the instruction that immediately succeeded the original
// instruction.
//
bool llvm::dceInstruction(BasicBlock::iterator &BBI) {
// Look for un"used" definitions...
if (isInstructionTriviallyDead(BBI)) {
BBI = BBI->getParent()->getInstList().erase(BBI); // Bye bye
return true;
/// RecursivelyDeleteTriviallyDeadInstructions - If the specified value is a
/// trivially dead instruction, delete it. If that makes any of its operands
/// trivially dead, delete them too, recursively.
void llvm::RecursivelyDeleteTriviallyDeadInstructions(Value *V) {
Instruction *I = dyn_cast<Instruction>(V);
if (!I || !I->use_empty()) return;
SmallPtrSet<Instruction*, 16> Insts;
Insts.insert(I);
while (!Insts.empty()) {
I = *Insts.begin();
Insts.erase(I);
if (isInstructionTriviallyDead(I)) {
for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
if (Instruction *U = dyn_cast<Instruction>(I->getOperand(i)))
Insts.insert(U);
I->eraseFromParent();
}
}
return false;
}
//===----------------------------------------------------------------------===//
// Control Flow Graph Restructuring...
//