Author: evancheng
Date: Wed Dec 5 17:58:20 2007
New Revision: 44643
URL: http://llvm.org/viewvc/llvm-project?rev=44643&view=rev
Log:
If both result of the {s|z}xt and its source are live out, rewrite all uses of
the source with result of extension.
Modified:
llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp
Modified: llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp
URL:
http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp?rev=44643&r1=44642&r2=44643&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/CodeGenPrepare.cpp Wed Dec 5 17:58:20 2007
@@ -28,11 +28,17 @@
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallSet.h"
-#include "llvm/Support/Debug.h"
+#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Compiler.h"
+#include "llvm/Support/Debug.h"
#include "llvm/Support/GetElementPtrTypeIterator.h"
using namespace llvm;
+namespace {
+ cl::opt<bool> OptExtUses("optimize-ext-uses",
+ cl::init(false), cl::Hidden);
+}
+
namespace {
class VISIBILITY_HIDDEN CodeGenPrepare : public FunctionPass {
/// TLI - Keep a pointer of a TargetLowering to consult for determining
@@ -52,6 +58,7 @@
bool OptimizeLoadStoreInst(Instruction *I, Value *Addr,
const Type *AccessTy,
DenseMap<Value*,Value*> &SunkAddrs);
+ bool OptimizeExtUses(Instruction *I);
};
}
@@ -913,6 +920,61 @@
return true;
}
+bool CodeGenPrepare::OptimizeExtUses(Instruction *I) {
+ BasicBlock *DefBB = I->getParent();
+
+ // If both result of the {s|z}xt and its source are live out, rewrite all
+ // other uses of the source with result of extension.
+ Value *Src = I->getOperand(0);
+ if (Src->hasOneUse())
+ return false;
+
+ bool DefIsLiveOut = false;
+ for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
+ UI != E; ++UI) {
+ Instruction *User = cast<Instruction>(*UI);
+
+ // Figure out which BB this ext is used in.
+ BasicBlock *UserBB = User->getParent();
+ if (UserBB == DefBB) continue;
+ DefIsLiveOut = true;
+ break;
+ }
+ if (!DefIsLiveOut)
+ return false;
+
+ // InsertedTruncs - Only insert one trunc in each block once.
+ DenseMap<BasicBlock*, Instruction*> InsertedTruncs;
+
+ bool MadeChange = false;
+ for (Value::use_iterator UI = Src->use_begin(), E = Src->use_end();
+ UI != E; ++UI) {
+ Use &TheUse = UI.getUse();
+ Instruction *User = cast<Instruction>(*UI);
+
+ // Figure out which BB this ext is used in.
+ BasicBlock *UserBB = User->getParent();
+ if (UserBB == DefBB) continue;
+
+ // Both src and def are live in this block. Rewrite the use.
+ Instruction *&InsertedTrunc = InsertedTruncs[UserBB];
+
+ if (!InsertedTrunc) {
+ BasicBlock::iterator InsertPt = UserBB->begin();
+ while (isa<PHINode>(InsertPt)) ++InsertPt;
+
+ InsertedTrunc = new TruncInst(I, Src->getType(), "", InsertPt);
+ }
+
+ // Replace a use of the {s|z}ext source with a use of the result.
+ TheUse = InsertedTrunc;
+
+ MadeChange = true;
+ }
+
+ return MadeChange;
+}
+
// In this pass we look for GEP and cast instructions that are used
// across basic blocks and rewrite them to improve basic-block-at-a-time
// selection.
@@ -948,8 +1010,14 @@
if (isa<Constant>(CI->getOperand(0)))
continue;
- if (TLI)
- MadeChange |= OptimizeNoopCopyExpression(CI, *TLI);
+ bool Change = false;
+ if (TLI) {
+ Change = OptimizeNoopCopyExpression(CI, *TLI);
+ MadeChange |= Change;
+ }
+
+ if (OptExtUses && !Change && (isa<ZExtInst>(I) || isa<SExtInst>(I)))
+ MadeChange |= OptimizeExtUses(I);
} else if (CmpInst *CI = dyn_cast<CmpInst>(I)) {
MadeChange |= OptimizeCmpExpression(CI);
} else if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
_______________________________________________
llvm-commits mailing list
llvm-commits@cs.uiuc.edu
http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
