mirror of
https://github.com/RPCS3/llvm-mirror.git
synced 2024-10-19 11:02:59 +02:00
implement enough of the memset inference algorithm to recognize and insert
memsets. This is still missing one important validity check, but this is enough
to compile stuff like this:
void test0(std::vector<char> &X) {
for (std::vector<char>::iterator I = X.begin(), E = X.end(); I != E; ++I)
*I = 0;
}
void test1(std::vector<int> &X) {
for (long i = 0, e = X.size(); i != e; ++i)
X[i] = 0x01010101;
}
With:
$ clang t.cpp -S -o - -O2 -emit-llvm | opt -loop-idiom | opt -O3 | llc
to:
__Z5test0RSt6vectorIcSaIcEE: ## @_Z5test0RSt6vectorIcSaIcEE
## BB#0: ## %entry
subq $8, %rsp
movq (%rdi), %rax
movq 8(%rdi), %rsi
cmpq %rsi, %rax
je LBB0_2
## BB#1: ## %bb.nph
subq %rax, %rsi
movq %rax, %rdi
callq ___bzero
LBB0_2: ## %for.end
addq $8, %rsp
ret
...
__Z5test1RSt6vectorIiSaIiEE: ## @_Z5test1RSt6vectorIiSaIiEE
## BB#0: ## %entry
subq $8, %rsp
movq (%rdi), %rax
movq 8(%rdi), %rdx
subq %rax, %rdx
cmpq $4, %rdx
jb LBB1_2
## BB#1: ## %for.body.preheader
andq $-4, %rdx
movl $1, %esi
movq %rax, %rdi
callq _memset
LBB1_2: ## %for.end
addq $8, %rsp
ret
llvm-svn: 122573
This commit is contained in:
Chris Lattner
parent
9007b56712
commit
d4daf9f002
@ -539,8 +539,7 @@ namespace llvm {
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/// getMinusSCEV - Return LHS-RHS.
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///
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const SCEV *getMinusSCEV(const SCEV *LHS,
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const SCEV *RHS);
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const SCEV *getMinusSCEV(const SCEV *LHS, const SCEV *RHS);
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/// getTruncateOrZeroExtend - Return a SCEV corresponding to a conversion
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/// of the input value to the specified type. If the type must be
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@ -17,9 +17,11 @@
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#include "llvm/Transforms/Scalar.h"
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#include "llvm/Analysis/LoopPass.h"
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#include "llvm/Analysis/ScalarEvolutionExpressions.h"
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#include "llvm/Analysis/ScalarEvolutionExpander.h"
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#include "llvm/Analysis/ValueTracking.h"
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#include "llvm/Target/TargetData.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/IRBuilder.h"
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#include "llvm/Support/raw_ostream.h"
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using namespace llvm;
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@ -41,6 +43,11 @@ namespace {
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bool processLoopStore(StoreInst *SI, const SCEV *BECount);
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bool processLoopStoreOfSplatValue(StoreInst *SI, unsigned StoreSize,
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Value *SplatValue,
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const SCEVAddRecExpr *Ev,
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const SCEV *BECount);
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/// This transformation requires natural loop information & requires that
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/// loop preheaders be inserted into the CFG.
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///
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@ -96,8 +103,11 @@ bool LoopIdiomRecognize::runOnLoop(Loop *L, LPPassManager &LPM) {
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bool MadeChange = false;
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for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ) {
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// Look for store instructions, which may be memsets.
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if (StoreInst *SI = dyn_cast<StoreInst>(I++))
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MadeChange |= processLoopStore(SI, BECount);
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StoreInst *SI = dyn_cast<StoreInst>(I++);
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if (SI == 0 || SI->isVolatile()) continue;
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MadeChange |= processLoopStore(SI, BECount);
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}
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return MadeChange;
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@ -106,6 +116,7 @@ bool LoopIdiomRecognize::runOnLoop(Loop *L, LPPassManager &LPM) {
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/// scanBlock - Look over a block to see if we can promote anything out of it.
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bool LoopIdiomRecognize::processLoopStore(StoreInst *SI, const SCEV *BECount) {
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Value *StoredVal = SI->getValueOperand();
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Value *StorePtr = SI->getPointerOperand();
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// Check to see if the store updates all bits in memory. We don't want to
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// process things like a store of i3. We also require that the store be a
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@ -118,8 +129,7 @@ bool LoopIdiomRecognize::processLoopStore(StoreInst *SI, const SCEV *BECount) {
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// See if the pointer expression is an AddRec like {base,+,1} on the current
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// loop, which indicates a strided store. If we have something else, it's a
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// random store we can't handle.
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const SCEVAddRecExpr *Ev =
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dyn_cast<SCEVAddRecExpr>(SE->getSCEV(SI->getPointerOperand()));
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const SCEVAddRecExpr *Ev = dyn_cast<SCEVAddRecExpr>(SE->getSCEV(StorePtr));
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if (Ev == 0 || Ev->getLoop() != CurLoop || !Ev->isAffine())
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return false;
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@ -130,18 +140,75 @@ bool LoopIdiomRecognize::processLoopStore(StoreInst *SI, const SCEV *BECount) {
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if (Stride == 0 || StoreSize != Stride->getValue()->getValue())
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return false;
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errs() << "Found strided store: " << *Ev << "\n";
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// Check for memcpy here.
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// If the stored value is a byte-wise value (like i32 -1), then it may be
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// turned into a memset of i8 -1, assuming that all the consequtive bytes
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// are stored. A store of i32 0x01020304 can never be turned into a memset.
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Value *SplatValue = isBytewiseValue(StoredVal);
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if (SplatValue == 0) return false;
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if (Value *SplatValue = isBytewiseValue(StoredVal))
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return processLoopStoreOfSplatValue(SI, StoreSize, SplatValue, Ev, BECount);
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// Handle the memcpy case here.
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errs() << "Found strided store: " << *Ev << "\n";
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return false;
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}
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/// processLoopStoreOfSplatValue - We see a strided store of a memsetable value.
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/// If we can transform this into a memset in the loop preheader, do so.
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bool LoopIdiomRecognize::
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processLoopStoreOfSplatValue(StoreInst *SI, unsigned StoreSize,
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Value *SplatValue,
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const SCEVAddRecExpr *Ev, const SCEV *BECount) {
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// Okay, we have a strided store "p[i]" of a splattable value. We can turn
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// this into a memset in the loop preheader now if we want. However, this
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// would be unsafe to do if there is anything else in the loop that may read
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// or write to the aliased location. Check for an alias.
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// FIXME: TODO safety check.
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// Okay, everything looks good, insert the memset.
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BasicBlock *Preheader = CurLoop->getLoopPreheader();
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IRBuilder<> Builder(Preheader->getTerminator());
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// The trip count of the loop and the base pointer of the addrec SCEV is
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// guaranteed to be loop invariant, which means that it should dominate the
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// header. Just insert code for it in the preheader.
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SCEVExpander Expander(*SE);
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unsigned AddrSpace = SI->getPointerAddressSpace();
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Value *BasePtr =
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Expander.expandCodeFor(Ev->getStart(), Builder.getInt8PtrTy(AddrSpace),
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Preheader->getTerminator());
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// The # stored bytes is (BECount+1)*Size. Expand the trip count out to
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// pointer size if it isn't already.
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const Type *IntPtr = TD->getIntPtrType(SI->getContext());
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unsigned BESize = SE->getTypeSizeInBits(BECount->getType());
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if (BESize < TD->getPointerSizeInBits())
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BECount = SE->getZeroExtendExpr(BECount, IntPtr);
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else if (BESize > TD->getPointerSizeInBits())
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BECount = SE->getTruncateExpr(BECount, IntPtr);
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const SCEV *NumBytesS = SE->getAddExpr(BECount, SE->getConstant(IntPtr, 1),
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true, true /*nooverflow*/);
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if (StoreSize != 1)
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NumBytesS = SE->getMulExpr(NumBytesS, SE->getConstant(IntPtr, StoreSize),
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true, true /*nooverflow*/);
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Value *NumBytes =
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Expander.expandCodeFor(NumBytesS, IntPtr, Preheader->getTerminator());
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Value *NewCall =
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Builder.CreateMemSet(BasePtr, SplatValue, NumBytes, SI->getAlignment());
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DEBUG(dbgs() << " Formed memset: " << *NewCall << "\n"
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<< " from store to: " << *Ev << " at: " << *SI << "\n");
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// Okay, the memset has been formed. Zap the original store.
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// FIXME: We want to recursively delete dead instructions, but we have to
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// update SCEV.
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SI->eraseFromParent();
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return true;
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}
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44
test/Transforms/LoopIdiom/basic.ll
Normal file
44
test/Transforms/LoopIdiom/basic.ll
Normal file
@ -0,0 +1,44 @@
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; RUN: opt -loop-idiom < %s -S | FileCheck %s
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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"
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target triple = "x86_64-apple-darwin10.0.0"
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define void @test1(i8* %Base, i64 %Size) nounwind ssp {
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bb.nph: ; preds = %entry
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br label %for.body
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for.body: ; preds = %bb.nph, %for.body
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%indvar = phi i64 [ 0, %bb.nph ], [ %indvar.next, %for.body ]
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%I.0.014 = getelementptr i8* %Base, i64 %indvar
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store i8 0, i8* %I.0.014, align 1
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%indvar.next = add i64 %indvar, 1
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%exitcond = icmp eq i64 %indvar.next, %Size
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br i1 %exitcond, label %for.end, label %for.body
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for.end: ; preds = %for.body, %entry
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ret void
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; CHECK: @test1
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; CHECK: call void @llvm.memset.p0i8.i64(i8* %Base, i8 0, i64 %Size, i32 1, i1 false)
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; CHECK-NOT: store
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}
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define void @test2(i32* %Base, i64 %Size) nounwind ssp {
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entry:
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%cmp10 = icmp eq i64 %Size, 0
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br i1 %cmp10, label %for.end, label %for.body
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for.body: ; preds = %entry, %for.body
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%i.011 = phi i64 [ %inc, %for.body ], [ 0, %entry ]
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%add.ptr.i = getelementptr i32* %Base, i64 %i.011
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store i32 16843009, i32* %add.ptr.i, align 4
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%inc = add nsw i64 %i.011, 1
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%exitcond = icmp eq i64 %inc, %Size
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br i1 %exitcond, label %for.end, label %for.body
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for.end: ; preds = %for.body, %entry
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ret void
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; CHECK: @test2
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; CHECK: br i1 %cmp10,
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; CHECK: %tmp = mul i64 %Size, 4
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; CHECK: call void @llvm.memset.p0i8.i64(i8* %Base1, i8 1, i64 %tmp, i32 4, i1 false)
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; CHECK-NOT: store
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}
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3
test/Transforms/LoopIdiom/dg.exp
Normal file
3
test/Transforms/LoopIdiom/dg.exp
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@ -0,0 +1,3 @@
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load_lib llvm.exp
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RunLLVMTests [lsort [glob -nocomplain $srcdir/$subdir/*.{ll,c,cpp}]]
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