[llvm-commits] [llvm] r85144 - in /llvm/trunk: include/llvm/LinkAllPasses.h include/llvm/Transforms/Scalar.h lib/Transforms/Scalar/GEPSplitter.cpp
Dan Gohman
gohman at apple.com
Mon Oct 26 12:12:14 PDT 2009
Author: djg
Date: Mon Oct 26 14:12:14 2009
New Revision: 85144
URL: http://llvm.org/viewvc/llvm-project?rev=85144&view=rev
Log:
Check in the experimental GEP splitter pass. This pass splits complex
GEPs (more than one non-zero index) into simple GEPs (at most one
non-zero index). In some simple experiments using this it's not
uncommon to see 3% overall code size wins, because it exposes
redundancies that can be eliminated, however it's tricky to use
because instcombine aggressively undoes the work that this pass does.
Added:
llvm/trunk/lib/Transforms/Scalar/GEPSplitter.cpp
Modified:
llvm/trunk/include/llvm/LinkAllPasses.h
llvm/trunk/include/llvm/Transforms/Scalar.h
Modified: llvm/trunk/include/llvm/LinkAllPasses.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/LinkAllPasses.h?rev=85144&r1=85143&r2=85144&view=diff
==============================================================================
--- llvm/trunk/include/llvm/LinkAllPasses.h (original)
+++ llvm/trunk/include/llvm/LinkAllPasses.h Mon Oct 26 14:12:14 2009
@@ -141,6 +141,7 @@
(void) llvm::createPartialInliningPass();
(void) llvm::createSSIPass();
(void) llvm::createSSIEverythingPass();
+ (void) llvm::createGEPSplitterPass();
(void)new llvm::IntervalPartition();
(void)new llvm::FindUsedTypes();
Modified: llvm/trunk/include/llvm/Transforms/Scalar.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Transforms/Scalar.h?rev=85144&r1=85143&r2=85144&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Transforms/Scalar.h (original)
+++ llvm/trunk/include/llvm/Transforms/Scalar.h Mon Oct 26 14:12:14 2009
@@ -341,6 +341,12 @@
//
FunctionPass *createSSIEverythingPass();
+//===----------------------------------------------------------------------===//
+//
+// GEPSplitter - Split complex GEPs into simple ones
+//
+FunctionPass *createGEPSplitterPass();
+
} // End llvm namespace
#endif
Added: llvm/trunk/lib/Transforms/Scalar/GEPSplitter.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/GEPSplitter.cpp?rev=85144&view=auto
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/GEPSplitter.cpp (added)
+++ llvm/trunk/lib/Transforms/Scalar/GEPSplitter.cpp Mon Oct 26 14:12:14 2009
@@ -0,0 +1,81 @@
+//===- GEPSplitter.cpp - Split complex GEPs into simple ones --------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This function breaks GEPs with more than 2 non-zero operands into smaller
+// GEPs each with no more than 2 non-zero operands. This exposes redundancy
+// between GEPs with common initial operand sequences.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "split-geps"
+#include "llvm/Transforms/Scalar.h"
+#include "llvm/Constants.h"
+#include "llvm/Function.h"
+#include "llvm/Instructions.h"
+#include "llvm/Pass.h"
+using namespace llvm;
+
+namespace {
+ class GEPSplitter : public FunctionPass {
+ virtual bool runOnFunction(Function &F);
+ virtual void getAnalysisUsage(AnalysisUsage &AU) const;
+ public:
+ static char ID; // Pass identification, replacement for typeid
+ explicit GEPSplitter() : FunctionPass(&ID) {}
+ };
+}
+
+char GEPSplitter::ID = 0;
+static RegisterPass<GEPSplitter> X("split-geps",
+ "split complex GEPs into simple GEPs");
+
+FunctionPass *llvm::createGEPSplitterPass() {
+ return new GEPSplitter();
+}
+
+bool GEPSplitter::runOnFunction(Function &F) {
+ bool Changed = false;
+
+ // Visit each GEP instruction.
+ for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
+ for (BasicBlock::iterator II = I->begin(), IE = I->end(); II != IE; )
+ if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(II++)) {
+ unsigned NumOps = GEP->getNumOperands();
+ // Ignore GEPs which are already simple.
+ if (NumOps <= 2)
+ continue;
+ bool FirstIndexIsZero = isa<ConstantInt>(GEP->getOperand(1)) &&
+ cast<ConstantInt>(GEP->getOperand(1))->isZero();
+ if (NumOps == 3 && FirstIndexIsZero)
+ continue;
+ // The first index is special and gets expanded with a 2-operand GEP
+ // (unless it's zero, in which case we can skip this).
+ Value *NewGEP = FirstIndexIsZero ?
+ GEP->getOperand(0) :
+ GetElementPtrInst::Create(GEP->getOperand(0), GEP->getOperand(1),
+ "tmp", GEP);
+ // All remaining indices get expanded with a 3-operand GEP with zero
+ // as the second operand.
+ Value *Idxs[2];
+ Idxs[0] = ConstantInt::get(Type::getInt64Ty(F.getContext()), 0);
+ for (unsigned i = 2; i != NumOps; ++i) {
+ Idxs[1] = GEP->getOperand(i);
+ NewGEP = GetElementPtrInst::Create(NewGEP, Idxs, Idxs+2, "tmp", GEP);
+ }
+ GEP->replaceAllUsesWith(NewGEP);
+ GEP->eraseFromParent();
+ Changed = true;
+ }
+
+ return Changed;
+}
+
+void GEPSplitter::getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.setPreservesCFG();
+}
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