diff options
| -rw-r--r-- | include/llvm/Analysis/ScalarEvolution.h | 3 | ||||
| -rw-r--r-- | lib/Transforms/Scalar/LoopIdiomRecognize.cpp | 89 | ||||
| -rw-r--r-- | test/Transforms/LoopIdiom/basic.ll | 44 | ||||
| -rw-r--r-- | test/Transforms/LoopIdiom/dg.exp | 3 |
4 files changed, 126 insertions, 13 deletions
diff --git a/include/llvm/Analysis/ScalarEvolution.h b/include/llvm/Analysis/ScalarEvolution.h index 38c50d1fbe..d910406771 100644 --- a/include/llvm/Analysis/ScalarEvolution.h +++ b/include/llvm/Analysis/ScalarEvolution.h @@ -539,8 +539,7 @@ namespace llvm { /// getMinusSCEV - Return LHS-RHS. /// - const SCEV *getMinusSCEV(const SCEV *LHS, - const SCEV *RHS); + const SCEV *getMinusSCEV(const SCEV *LHS, const SCEV *RHS); /// getTruncateOrZeroExtend - Return a SCEV corresponding to a conversion /// of the input value to the specified type. If the type must be diff --git a/lib/Transforms/Scalar/LoopIdiomRecognize.cpp b/lib/Transforms/Scalar/LoopIdiomRecognize.cpp index eb7d4930ed..a5e2b2dba1 100644 --- a/lib/Transforms/Scalar/LoopIdiomRecognize.cpp +++ b/lib/Transforms/Scalar/LoopIdiomRecognize.cpp @@ -17,9 +17,11 @@ #include "llvm/Transforms/Scalar.h" #include "llvm/Analysis/LoopPass.h" #include "llvm/Analysis/ScalarEvolutionExpressions.h" +#include "llvm/Analysis/ScalarEvolutionExpander.h" #include "llvm/Analysis/ValueTracking.h" #include "llvm/Target/TargetData.h" #include "llvm/Support/Debug.h" +#include "llvm/Support/IRBuilder.h" #include "llvm/Support/raw_ostream.h" using namespace llvm; @@ -41,6 +43,11 @@ namespace { bool processLoopStore(StoreInst *SI, const SCEV *BECount); + bool processLoopStoreOfSplatValue(StoreInst *SI, unsigned StoreSize, + Value *SplatValue, + const SCEVAddRecExpr *Ev, + const SCEV *BECount); + /// This transformation requires natural loop information & requires that /// loop preheaders be inserted into the CFG. /// @@ -96,8 +103,11 @@ bool LoopIdiomRecognize::runOnLoop(Loop *L, LPPassManager &LPM) { bool MadeChange = false; for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ) { // Look for store instructions, which may be memsets. - if (StoreInst *SI = dyn_cast<StoreInst>(I++)) - MadeChange |= processLoopStore(SI, BECount); + StoreInst *SI = dyn_cast<StoreInst>(I++); + if (SI == 0 || SI->isVolatile()) continue; + + + MadeChange |= processLoopStore(SI, BECount); } return MadeChange; @@ -106,6 +116,7 @@ bool LoopIdiomRecognize::runOnLoop(Loop *L, LPPassManager &LPM) { /// scanBlock - Look over a block to see if we can promote anything out of it. bool LoopIdiomRecognize::processLoopStore(StoreInst *SI, const SCEV *BECount) { Value *StoredVal = SI->getValueOperand(); + Value *StorePtr = SI->getPointerOperand(); // Check to see if the store updates all bits in memory. We don't want to // process things like a store of i3. We also require that the store be a @@ -118,8 +129,7 @@ bool LoopIdiomRecognize::processLoopStore(StoreInst *SI, const SCEV *BECount) { // See if the pointer expression is an AddRec like {base,+,1} on the current // loop, which indicates a strided store. If we have something else, it's a // random store we can't handle. - const SCEVAddRecExpr *Ev = - dyn_cast<SCEVAddRecExpr>(SE->getSCEV(SI->getPointerOperand())); + const SCEVAddRecExpr *Ev = dyn_cast<SCEVAddRecExpr>(SE->getSCEV(StorePtr)); if (Ev == 0 || Ev->getLoop() != CurLoop || !Ev->isAffine()) return false; @@ -130,18 +140,75 @@ bool LoopIdiomRecognize::processLoopStore(StoreInst *SI, const SCEV *BECount) { if (Stride == 0 || StoreSize != Stride->getValue()->getValue()) return false; - errs() << "Found strided store: " << *Ev << "\n"; - - // Check for memcpy here. - - // If the stored value is a byte-wise value (like i32 -1), then it may be // turned into a memset of i8 -1, assuming that all the consequtive bytes // are stored. A store of i32 0x01020304 can never be turned into a memset. - Value *SplatValue = isBytewiseValue(StoredVal); - if (SplatValue == 0) return false; + if (Value *SplatValue = isBytewiseValue(StoredVal)) + return processLoopStoreOfSplatValue(SI, StoreSize, SplatValue, Ev, BECount); + + // Handle the memcpy case here. + errs() << "Found strided store: " << *Ev << "\n"; return false; } +/// processLoopStoreOfSplatValue - We see a strided store of a memsetable value. +/// If we can transform this into a memset in the loop preheader, do so. +bool LoopIdiomRecognize:: +processLoopStoreOfSplatValue(StoreInst *SI, unsigned StoreSize, + Value *SplatValue, + const SCEVAddRecExpr *Ev, const SCEV *BECount) { + // Okay, we have a strided store "p[i]" of a splattable value. We can turn + // this into a memset in the loop preheader now if we want. However, this + // would be unsafe to do if there is anything else in the loop that may read + // or write to the aliased location. Check for an alias. + + // FIXME: TODO safety check. + + // Okay, everything looks good, insert the memset. + BasicBlock *Preheader = CurLoop->getLoopPreheader(); + + IRBuilder<> Builder(Preheader->getTerminator()); + + // The trip count of the loop and the base pointer of the addrec SCEV is + // guaranteed to be loop invariant, which means that it should dominate the + // header. Just insert code for it in the preheader. + SCEVExpander Expander(*SE); + + unsigned AddrSpace = SI->getPointerAddressSpace(); + Value *BasePtr = + Expander.expandCodeFor(Ev->getStart(), Builder.getInt8PtrTy(AddrSpace), + Preheader->getTerminator()); + + // The # stored bytes is (BECount+1)*Size. Expand the trip count out to + // pointer size if it isn't already. + const Type *IntPtr = TD->getIntPtrType(SI->getContext()); + unsigned BESize = SE->getTypeSizeInBits(BECount->getType()); + if (BESize < TD->getPointerSizeInBits()) + BECount = SE->getZeroExtendExpr(BECount, IntPtr); + else if (BESize > TD->getPointerSizeInBits()) + BECount = SE->getTruncateExpr(BECount, IntPtr); + + const SCEV *NumBytesS = SE->getAddExpr(BECount, SE->getConstant(IntPtr, 1), + true, true /*nooverflow*/); + if (StoreSize != 1) + NumBytesS = SE->getMulExpr(NumBytesS, SE->getConstant(IntPtr, StoreSize), + true, true /*nooverflow*/); + + Value *NumBytes = + Expander.expandCodeFor(NumBytesS, IntPtr, Preheader->getTerminator()); + + Value *NewCall = + Builder.CreateMemSet(BasePtr, SplatValue, NumBytes, SI->getAlignment()); + + DEBUG(dbgs() << " Formed memset: " << *NewCall << "\n" + << " from store to: " << *Ev << " at: " << *SI << "\n"); + + // Okay, the memset has been formed. Zap the original store. + // FIXME: We want to recursively delete dead instructions, but we have to + // update SCEV. + SI->eraseFromParent(); + return true; +} + diff --git a/test/Transforms/LoopIdiom/basic.ll b/test/Transforms/LoopIdiom/basic.ll new file mode 100644 index 0000000000..f694474a6c --- /dev/null +++ b/test/Transforms/LoopIdiom/basic.ll @@ -0,0 +1,44 @@ +; RUN: opt -loop-idiom < %s -S | FileCheck %s +target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64" +target triple = "x86_64-apple-darwin10.0.0" + +define void @test1(i8* %Base, i64 %Size) nounwind ssp { +bb.nph: ; preds = %entry + br label %for.body + +for.body: ; preds = %bb.nph, %for.body + %indvar = phi i64 [ 0, %bb.nph ], [ %indvar.next, %for.body ] + %I.0.014 = getelementptr i8* %Base, i64 %indvar + store i8 0, i8* %I.0.014, align 1 + %indvar.next = add i64 %indvar, 1 + %exitcond = icmp eq i64 %indvar.next, %Size + br i1 %exitcond, label %for.end, label %for.body + +for.end: ; preds = %for.body, %entry + ret void +; CHECK: @test1 +; CHECK: call void @llvm.memset.p0i8.i64(i8* %Base, i8 0, i64 %Size, i32 1, i1 false) +; CHECK-NOT: store +} + +define void @test2(i32* %Base, i64 %Size) nounwind ssp { +entry: + %cmp10 = icmp eq i64 %Size, 0 + br i1 %cmp10, label %for.end, label %for.body + +for.body: ; preds = %entry, %for.body + %i.011 = phi i64 [ %inc, %for.body ], [ 0, %entry ] + %add.ptr.i = getelementptr i32* %Base, i64 %i.011 + store i32 16843009, i32* %add.ptr.i, align 4 + %inc = add nsw i64 %i.011, 1 + %exitcond = icmp eq i64 %inc, %Size + br i1 %exitcond, label %for.end, label %for.body + +for.end: ; preds = %for.body, %entry + ret void +; CHECK: @test2 +; CHECK: br i1 %cmp10, +; CHECK: %tmp = mul i64 %Size, 4 +; CHECK: call void @llvm.memset.p0i8.i64(i8* %Base1, i8 1, i64 %tmp, i32 4, i1 false) +; CHECK-NOT: store +} diff --git a/test/Transforms/LoopIdiom/dg.exp b/test/Transforms/LoopIdiom/dg.exp new file mode 100644 index 0000000000..f2005891a5 --- /dev/null +++ b/test/Transforms/LoopIdiom/dg.exp @@ -0,0 +1,3 @@ +load_lib llvm.exp + +RunLLVMTests [lsort [glob -nocomplain $srcdir/$subdir/*.{ll,c,cpp}]] |