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Fix a case where SROA did not correctly detect dead PHI or selects due
to chains or cycles between PHIs and/or selects. Also add a couple of really nice test cases reduced from Kostya's reports in PR13905 and PR13906. Both are fixed by this patch. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@164596 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -522,8 +522,10 @@ private:
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void insertUse(Instruction &I, int64_t Offset, uint64_t Size,
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bool IsSplittable = false) {
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// Completely skip uses which don't overlap the allocation.
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if ((Offset >= 0 && (uint64_t)Offset >= AllocSize) ||
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// Completely skip uses which have a zero size or don't overlap the
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// allocation.
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if (Size == 0 ||
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(Offset >= 0 && (uint64_t)Offset >= AllocSize) ||
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(Offset < 0 && (uint64_t)-Offset >= Size)) {
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DEBUG(dbgs() << "WARNING: Ignoring " << Size << " byte use @" << Offset
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<< " which starts past the end of the " << AllocSize
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@ -697,6 +699,9 @@ private:
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SmallVector<std::pair<Instruction *, Instruction *>, 4> Uses;
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Visited.insert(Root);
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Uses.push_back(std::make_pair(cast<Instruction>(*U), Root));
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// If there are no loads or stores, the access is dead. We mark that as
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// a size zero access.
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Size = 0;
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do {
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Instruction *I, *UsedI;
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llvm::tie(UsedI, I) = Uses.pop_back_val();
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@ -824,9 +829,9 @@ private:
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}
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void insertUse(Instruction &User, int64_t Offset, uint64_t Size) {
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// If the use extends outside of the allocation, record it as a dead use
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// for elimination later.
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if ((uint64_t)Offset >= AllocSize ||
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// If the use has a zero size or extends outside of the allocation, record
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// it as a dead use for elimination later.
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if (Size == 0 || (uint64_t)Offset >= AllocSize ||
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(Offset < 0 && (uint64_t)-Offset >= Size))
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return markAsDead(User);
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@ -327,3 +327,48 @@ exit:
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%load = load i32* %a
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ret i32 %load
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}
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define i32 @PR13905() {
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; Check a pattern where we have a chain of dead phi nodes to ensure they are
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; deleted and promotion can proceed.
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; CHECK: @PR13905
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; CHECK-NOT: alloca i32
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; CHECK: ret i32 undef
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entry:
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%h = alloca i32
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store i32 0, i32* %h
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br i1 undef, label %loop1, label %exit
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loop1:
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%phi1 = phi i32* [ null, %entry ], [ %h, %loop1 ], [ %h, %loop2 ]
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br i1 undef, label %loop1, label %loop2
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loop2:
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br i1 undef, label %loop1, label %exit
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exit:
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%phi2 = phi i32* [ %phi1, %loop2 ], [ null, %entry ]
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ret i32 undef
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}
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define i32 @PR13906() {
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; Another pattern which can lead to crashes due to failing to clear out dead
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; PHI nodes or select nodes. This triggers subtly differently from the above
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; cases because the PHI node is (recursively) alive, but the select is dead.
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; CHECK: @PR13906
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; CHECK-NOT: alloca
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entry:
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%c = alloca i32
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store i32 0, i32* %c
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br label %for.cond
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for.cond:
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%d.0 = phi i32* [ undef, %entry ], [ %c, %if.then ], [ %d.0, %for.cond ]
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br i1 undef, label %if.then, label %for.cond
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if.then:
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%tmpcast.d.0 = select i1 undef, i32* %c, i32* %d.0
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br label %for.cond
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}
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