remove doConstantPropagation and dceInstruction, they are just
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
diff --git a/lib/Transforms/Utils/Local.cpp b/lib/Transforms/Utils/Local.cpp
index efb9022..e3a0917 100644
--- a/lib/Transforms/Utils/Local.cpp
+++ b/lib/Transforms/Utils/Local.cpp
@@ -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 @@
// 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 @@
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...
//