[llvm-commits] CVS: llvm/lib/Transforms/Utils/Local.cpp
Chris Lattner
lattner at cs.uiuc.edu
Thu Dec 18 23:58:02 PST 2003
Changes in directory llvm/lib/Transforms/Utils:
Local.cpp updated: 1.12 -> 1.13
---
Log message:
Add new function
---
Diffs of the changes: (+41 -10)
Index: llvm/lib/Transforms/Utils/Local.cpp
diff -u llvm/lib/Transforms/Utils/Local.cpp:1.12 llvm/lib/Transforms/Utils/Local.cpp:1.13
--- llvm/lib/Transforms/Utils/Local.cpp:1.12 Tue Nov 11 16:41:34 2003
+++ llvm/lib/Transforms/Utils/Local.cpp Thu Dec 18 23:56:28 2003
@@ -15,18 +15,18 @@
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/iTerminators.h"
#include "llvm/iOperators.h"
+#include "llvm/iPHINode.h"
#include "llvm/ConstantHandling.h"
-
-namespace llvm {
+using namespace llvm;
//===----------------------------------------------------------------------===//
// Local constant propagation...
//
-// ConstantFoldInstruction - If an instruction references constants, try to fold
-// them together...
-//
-bool doConstantPropagation(BasicBlock::iterator &II) {
+/// doConstantPropagation - If an instruction references constants, try to fold
+/// them together...
+///
+bool llvm::doConstantPropagation(BasicBlock::iterator &II) {
if (Constant *C = ConstantFoldInstruction(II)) {
// Replaces all of the uses of a variable with uses of the constant.
II->replaceAllUsesWith(C);
@@ -43,7 +43,7 @@
// constant value, convert it into an unconditional branch to the constant
// destination.
//
-bool ConstantFoldTerminator(BasicBlock *BB) {
+bool llvm::ConstantFoldTerminator(BasicBlock *BB) {
TerminatorInst *T = BB->getTerminator();
// Branch - See if we are conditional jumping on constant
@@ -165,7 +165,7 @@
// Local dead code elimination...
//
-bool isInstructionTriviallyDead(Instruction *I) {
+bool llvm::isInstructionTriviallyDead(Instruction *I) {
return I->use_empty() && !I->mayWriteToMemory() && !isa<TerminatorInst>(I);
}
@@ -174,7 +174,7 @@
// to point to the instruction that immediately succeeded the original
// instruction.
//
-bool dceInstruction(BasicBlock::iterator &BBI) {
+bool llvm::dceInstruction(BasicBlock::iterator &BBI) {
// Look for un"used" definitions...
if (isInstructionTriviallyDead(BBI)) {
BBI = BBI->getParent()->getInstList().erase(BBI); // Bye bye
@@ -183,4 +183,35 @@
return false;
}
-} // End llvm namespace
+//===----------------------------------------------------------------------===//
+// PHI Instruction Simplification
+//
+
+/// hasConstantValue - If the specified PHI node always merges together the same
+/// value, return the value, otherwise return null.
+///
+Value *llvm::hasConstantValue(PHINode *PN) {
+ // If the PHI node only has one incoming value, eliminate the PHI node...
+ if (PN->getNumIncomingValues() == 1)
+ return PN->getIncomingValue(0);
+
+ // Otherwise if all of the incoming values are the same for the PHI, replace
+ // the PHI node with the incoming value.
+ //
+ Value *InVal = 0;
+ for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
+ if (PN->getIncomingValue(i) != PN) // Not the PHI node itself...
+ if (InVal && PN->getIncomingValue(i) != InVal)
+ return 0; // Not the same, bail out.
+ else
+ InVal = PN->getIncomingValue(i);
+
+ // The only case that could cause InVal to be null is if we have a PHI node
+ // that only has entries for itself. In this case, there is no entry into the
+ // loop, so kill the PHI.
+ //
+ if (InVal == 0) InVal = Constant::getNullValue(PN->getType());
+
+ // All of the incoming values are the same, return the value now.
+ return InVal;
+}
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