diff options
| -rw-r--r-- | lib/Analysis/BasicAliasAnalysis.cpp | 35 | ||||
| -rw-r--r-- | test/Analysis/BasicAA/phi-speculation.ll | 33 |
2 files changed, 68 insertions, 0 deletions
diff --git a/lib/Analysis/BasicAliasAnalysis.cpp b/lib/Analysis/BasicAliasAnalysis.cpp index d537d63317..a3bc06a80f 100644 --- a/lib/Analysis/BasicAliasAnalysis.cpp +++ b/lib/Analysis/BasicAliasAnalysis.cpp @@ -1060,12 +1060,42 @@ BasicAliasAnalysis::aliasPHI(const PHINode *PN, uint64_t PNSize, // on corresponding edges. if (const PHINode *PN2 = dyn_cast<PHINode>(V2)) if (PN2->getParent() == PN->getParent()) { + LocPair Locs(Location(PN, PNSize, PNTBAAInfo), + Location(V2, V2Size, V2TBAAInfo)); + if (PN > V2) + std::swap(Locs.first, Locs.second); + AliasResult Alias = aliasCheck(PN->getIncomingValue(0), PNSize, PNTBAAInfo, PN2->getIncomingValueForBlock(PN->getIncomingBlock(0)), V2Size, V2TBAAInfo); if (Alias == MayAlias) return MayAlias; + + // If the first source of the PHI nodes NoAlias and the other inputs are + // the PHI node itself through some amount of recursion this does not add + // any new information so just return NoAlias. + // bb: + // ptr = ptr2 + 1 + // loop: + // ptr_phi = phi [bb, ptr], [loop, ptr_plus_one] + // ptr2_phi = phi [bb, ptr2], [loop, ptr2_plus_one] + // ... + // ptr_plus_one = gep ptr_phi, 1 + // ptr2_plus_one = gep ptr2_phi, 1 + // We assume for the recursion that the the phis (ptr_phi, ptr2_phi) do + // not alias each other. + bool ArePhisAssumedNoAlias = false; + AliasResult OrigAliasResult; + if (Alias == NoAlias) { + // Pretend the phis do not alias. + assert(AliasCache.count(Locs) && + "There must exist an entry for the phi node"); + OrigAliasResult = AliasCache[Locs]; + AliasCache[Locs] = NoAlias; + ArePhisAssumedNoAlias = true; + } + for (unsigned i = 1, e = PN->getNumIncomingValues(); i != e; ++i) { AliasResult ThisAlias = aliasCheck(PN->getIncomingValue(i), PNSize, PNTBAAInfo, @@ -1075,6 +1105,11 @@ BasicAliasAnalysis::aliasPHI(const PHINode *PN, uint64_t PNSize, if (Alias == MayAlias) break; } + + // Reset if speculation failed. + if (ArePhisAssumedNoAlias && Alias != NoAlias) + AliasCache[Locs] = OrigAliasResult; + return Alias; } diff --git a/test/Analysis/BasicAA/phi-speculation.ll b/test/Analysis/BasicAA/phi-speculation.ll new file mode 100644 index 0000000000..21c6592986 --- /dev/null +++ b/test/Analysis/BasicAA/phi-speculation.ll @@ -0,0 +1,33 @@ +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-S128" + +; RUN: opt < %s -basicaa -aa-eval -print-all-alias-modref-info -disable-output 2>&1 | FileCheck %s + +; ptr_phi and ptr2_phi do not alias. +; CHECK: NoAlias: i32* %ptr2_phi, i32* %ptr_phi + +define i32 @test_noalias(i32* %ptr2, i32 %count, i32* %coeff) { +entry: + %ptr = getelementptr inbounds i32* %ptr2, i64 1 + br label %while.body + +while.body: + %num = phi i32 [ %count, %entry ], [ %dec, %while.body ] + %ptr_phi = phi i32* [ %ptr, %entry ], [ %ptr_inc, %while.body ] + %ptr2_phi = phi i32* [ %ptr2, %entry ], [ %ptr2_inc, %while.body ] + %result.09 = phi i32 [ 0 , %entry ], [ %add, %while.body ] + %dec = add nsw i32 %num, -1 + %0 = load i32* %ptr_phi, align 4 + store i32 %0, i32* %ptr2_phi, align 4 + %1 = load i32* %coeff, align 4 + %2 = load i32* %ptr_phi, align 4 + %mul = mul nsw i32 %1, %2 + %add = add nsw i32 %mul, %result.09 + %tobool = icmp eq i32 %dec, 0 + %ptr_inc = getelementptr inbounds i32* %ptr_phi, i64 1 + %ptr2_inc = getelementptr inbounds i32* %ptr2_phi, i64 1 + br i1 %tobool, label %the_exit, label %while.body + +the_exit: + ret i32 %add +} |