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improve validity check to handle constant-trip-count loops more
aggressively. In practice, this doesn't help anything though, see the todo. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122660 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -193,8 +193,7 @@ bool LoopIdiomRecognize::processLoopStore(StoreInst *SI, const SCEV *BECount) {
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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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// errs() << "Found strided store: " << *Ev << "\n";
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return false;
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}
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@ -202,13 +201,23 @@ bool LoopIdiomRecognize::processLoopStore(StoreInst *SI, const SCEV *BECount) {
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/// mayLoopModRefLocation - Return true if the specified loop might do a load or
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/// store to the same location that the specified store could store to, which is
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/// a loop-strided access.
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static bool mayLoopModRefLocation(StoreInst *SI, Loop *L, AliasAnalysis &AA) {
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static bool mayLoopModRefLocation(StoreInst *SI, Loop *L, const SCEV *BECount,
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unsigned StoreSize, AliasAnalysis &AA) {
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// Get the location that may be stored across the loop. Since the access is
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// strided positively through memory, we say that the modified location starts
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// at the pointer and has infinite size.
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// TODO: Could improve this for constant trip-count loops.
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AliasAnalysis::Location StoreLoc =
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AliasAnalysis::Location(SI->getPointerOperand());
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uint64_t AccessSize = AliasAnalysis::UnknownSize;
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// If the loop iterates a fixed number of times, we can refine the access size
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// to be exactly the size of the memset, which is (BECount+1)*StoreSize
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if (const SCEVConstant *BECst = dyn_cast<SCEVConstant>(BECount))
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AccessSize = (BECst->getValue()->getZExtValue()+1)*StoreSize;
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// TODO: For this to be really effective, we have to dive into the pointer
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// operand in the store. Store to &A[i] of 100 will always return may alias
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// with store of &A[100], we need to StoreLoc to be "A" with size of 100,
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// which will then no-alias a store to &A[100].
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AliasAnalysis::Location StoreLoc(SI->getPointerOperand(), AccessSize);
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for (Loop::block_iterator BI = L->block_begin(), E = L->block_end(); BI != E;
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++BI)
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@ -234,7 +243,8 @@ processLoopStoreOfSplatValue(StoreInst *SI, unsigned StoreSize,
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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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bool Unsafe=mayLoopModRefLocation(SI, CurLoop, getAnalysis<AliasAnalysis>());
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bool Unsafe = mayLoopModRefLocation(SI, CurLoop, BECount, StoreSize,
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getAnalysis<AliasAnalysis>());
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SI->insertBefore(InstAfterStore);
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@ -1,4 +1,4 @@
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; RUN: opt -loop-idiom < %s -S | FileCheck %s
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; RUN: opt -basicaa -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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@ -65,3 +65,29 @@ for.end: ; preds = %entry
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; CHECK-NOT: memset
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; CHECK: ret void
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}
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;; TODO: We should be able to promote this memset. Not yet though.
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define void @test4(i8* %Base) nounwind ssp {
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bb.nph: ; preds = %entry
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%Base100 = getelementptr i8* %Base, i64 1000
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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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;; Store beyond the range memset, should be safe to promote.
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store i8 42, i8* %Base100
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%indvar.next = add i64 %indvar, 1
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%exitcond = icmp eq i64 %indvar.next, 100
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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-TODO: @test4
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; CHECK-TODO: call void @llvm.memset.p0i8.i64(i8* %Base, i8 0, i64 100, i32 1, i1 false)
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; CHECK-TODO-NOT: store
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}
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