diff --git a/llvm/include/llvm/Analysis/AliasAnalysis.h b/llvm/include/llvm/Analysis/AliasAnalysis.h --- a/llvm/include/llvm/Analysis/AliasAnalysis.h +++ b/llvm/include/llvm/Analysis/AliasAnalysis.h @@ -651,6 +651,11 @@ DominatorTree *DT) { return AA.callCapturesBefore(I, MemLoc, DT, AAQI); } + + /// Assume that values may come from different cycle iterations. + void enableCrossIterationMode() { + AAQI.MayBeCrossIteration = true; + } }; /// Temporary typedef for legacy code that uses a generic \c AliasAnalysis diff --git a/llvm/lib/Analysis/LoopAccessAnalysis.cpp b/llvm/lib/Analysis/LoopAccessAnalysis.cpp --- a/llvm/lib/Analysis/LoopAccessAnalysis.cpp +++ b/llvm/lib/Analysis/LoopAccessAnalysis.cpp @@ -622,7 +622,10 @@ AccessAnalysis(Loop *TheLoop, AAResults *AA, LoopInfo *LI, MemoryDepChecker::DepCandidates &DA, PredicatedScalarEvolution &PSE) - : TheLoop(TheLoop), BAA(*AA), AST(BAA), LI(LI), DepCands(DA), PSE(PSE) {} + : TheLoop(TheLoop), BAA(*AA), AST(BAA), LI(LI), DepCands(DA), PSE(PSE) { + // We're analyzing dependences across loop iterations. + BAA.enableCrossIterationMode(); + } /// Register a load and whether it is only read from. void addLoad(MemoryLocation &Loc, Type *AccessTy, bool IsReadOnly) { diff --git a/llvm/test/Analysis/LoopAccessAnalysis/select-dependence.ll b/llvm/test/Analysis/LoopAccessAnalysis/select-dependence.ll new file mode 100644 --- /dev/null +++ b/llvm/test/Analysis/LoopAccessAnalysis/select-dependence.ll @@ -0,0 +1,30 @@ +; RUN: opt -passes='print' -disable-output 2>&1 < %s | FileCheck %s + +; CHECK: Dependences: +; CHECK-NEXT: Unknown: +; CHECK-NEXT: %t63 = load double, ptr %t62, align 8 -> +; CHECK-NEXT: store double %t63, ptr %t64, align 8 + +define i32 @test() { + %a1 = alloca [128 x double], align 8 + %a2 = alloca [128 x double], align 8 + %a3 = alloca [128 x double], align 8 + %t30 = getelementptr double, ptr %a2, i64 -32 + br label %loop + +loop: + %t58 = phi i64 [ %t65, %loop ], [ 0, %0 ] + %t59 = icmp ule i64 %t58, 32 + %t60 = select i1 %t59, ptr %a1, ptr %t30 + %t62 = getelementptr inbounds double, ptr %t60, i64 %t58 + %t63 = load double, ptr %t62, align 8 + %t61 = select i1 %t59, ptr %a2, ptr %a3 + %t64 = getelementptr inbounds double, ptr %t61, i64 %t58 + store double %t63, ptr %t64, align 8 + %t65 = add nuw nsw i64 %t58, 1 + %t66 = icmp eq i64 %t65, 94 + br i1 %t66, label %exit, label %loop + +exit: + ret i32 0 +}