diff options
| -rw-r--r-- | llvm/lib/Transforms/Utils/SimplifyIndVar.cpp | 50 | ||||
| -rw-r--r-- | llvm/test/Transforms/IndVarSimplify/loop-invariant-conditions.ll | 22 |
2 files changed, 28 insertions, 44 deletions
diff --git a/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp b/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp index c39e7861c50..bceb02a3c21 100644 --- a/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp +++ b/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp @@ -182,7 +182,8 @@ bool SimplifyIndvar::makeIVComparisonInvariant(ICmpInst *ICmp, ICmpInst::Predicate InvariantPredicate; const SCEV *InvariantLHS, *InvariantRHS; - if (!isa<PHINode>(IVOperand)) + auto *PN = dyn_cast<PHINode>(IVOperand); + if (!PN) return false; if (!SE->isLoopInvariantPredicate(Pred, S, X, L, InvariantPredicate, InvariantLHS, InvariantRHS)) @@ -202,49 +203,10 @@ bool SimplifyIndvar::makeIVComparisonInvariant(ICmpInst *ICmp, NewRHS = ICmp->getOperand(S == InvariantRHS ? IVOperIdx : (1 - IVOperIdx)); - auto *PN = cast<PHINode>(IVOperand); - for (unsigned i = 0, e = PN->getNumIncomingValues(); - i != e && (!NewLHS || !NewRHS); - ++i) { - - // If this is a value incoming from the backedge, then it cannot be a loop - // invariant value (since we know that IVOperand is an induction variable). - if (L->contains(PN->getIncomingBlock(i))) - continue; - - // NB! This following assert does not fundamentally have to be true, but - // it is true today given how SCEV analyzes induction variables. - // Specifically, today SCEV will *not* recognize %iv as an induction - // variable in the following case: - // - // define void @f(i32 %k) { - // entry: - // br i1 undef, label %r, label %l - // - // l: - // %k.inc.l = add i32 %k, 1 - // br label %loop - // - // r: - // %k.inc.r = add i32 %k, 1 - // br label %loop - // - // loop: - // %iv = phi i32 [ %k.inc.l, %l ], [ %k.inc.r, %r ], [ %iv.inc, %loop ] - // %iv.inc = add i32 %iv, 1 - // br label %loop - // } - // - // but if it starts to, at some point, then the assertion below will have - // to be changed to a runtime check. - - Value *Incoming = PN->getIncomingValue(i); - -#ifndef NDEBUG - if (auto *I = dyn_cast<Instruction>(Incoming)) - assert(DT->dominates(I, ICmp) && "Should be a unique loop dominating value!"); -#endif - + // TODO: Support multiple entry loops? (We currently bail out of these in + // the IndVarSimplify pass) + if (auto *BB = L->getLoopPredecessor()) { + Value *Incoming = PN->getIncomingValue(PN->getBasicBlockIndex(BB)); const SCEV *IncomingS = SE->getSCEV(Incoming); if (!NewLHS && IncomingS == InvariantLHS) diff --git a/llvm/test/Transforms/IndVarSimplify/loop-invariant-conditions.ll b/llvm/test/Transforms/IndVarSimplify/loop-invariant-conditions.ll index eee321da239..1c8eb93869a 100644 --- a/llvm/test/Transforms/IndVarSimplify/loop-invariant-conditions.ll +++ b/llvm/test/Transforms/IndVarSimplify/loop-invariant-conditions.ll @@ -273,6 +273,28 @@ for.end: ; preds = %if.end, %entry ret void } +; check to handle loops without preheaders, but invariant operands +; (we handle this today by inserting a preheader) +define void @test9(i1 %cnd, i64 %start) { +; CHECK-LABEL: @test9 +; CHECK-LABEL: loop.preheader: +entry: + br i1 %cnd, label %entry1, label %entry2 +entry1: + br label %loop +entry2: + br label %loop +loop: + %indvars.iv = phi i64 [ %start, %entry1 ],[ %start, %entry2 ], [ %indvars.iv.next, %loop ] + %indvars.iv.next = add nsw i64 %indvars.iv, 1 +; CHECK: %cmp1 = icmp slt i64 %start, -1 + %cmp1 = icmp slt i64 %indvars.iv, -1 + br i1 %cmp1, label %for.end, label %loop + +for.end: ; preds = %if.end, %entry + ret void +} + !1 = !{i64 -1, i64 100} |
