175400a801
In general, it's difficult to poke the ConstantExpr code in CFLAA, since LLVM is so great at eagerly reducing ConstantExprs. :) Sadly, this only shows a functional difference from before the patch because CFLAA has some special logic around taking loads of non-pointers into account. Namely, with the broken select behavior, CFLAA will completely fail to take note of @g3. Since CFLAA doesn't have any record about @g3 when we do an alias query for @g3 and %a, it conservatively answers MayAlias. When we properly take @g3 into account with the new select logic, we get NoAlias for this query. I suspect that the aforementioned "special logic" isn't completely correct, but this test-case should prevent future wonky aliasing results from appearing for these flavors of ConstantExprs, so I think it's still worth having. llvm-svn: 332017
31 lines
1.2 KiB
LLVM
31 lines
1.2 KiB
LLVM
; RUN: opt %s -S -disable-basicaa -cfl-steens-aa -aa-eval -print-all-alias-modref-info 2>&1 | FileCheck %s
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;
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; Regression: we weren't properly checking constexpr selects.
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@g = extern_weak dso_local global i32, align 4
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@g2 = extern_weak dso_local global i32, align 4
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@g3 = extern_weak dso_local global i32, align 4
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; CHECK-LABEL: Function: foo
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; CHECK: NoAlias: i32* select (i1 icmp ne (i32* @g, i32* null), i32* @g2, i32* @g3), i32** %a
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; CHECK: NoAlias: i32* %b, i32** %a
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; CHECK: MayAlias: i32* %b, i32* select (i1 icmp ne (i32* @g, i32* null), i32* @g2, i32* @g3)
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; CHECK: NoAlias: i32* @g2, i32** %a
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; CHECK: MayAlias: i32* @g2, i32* select (i1 icmp ne (i32* @g, i32* null), i32* @g2, i32* @g3)
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; CHECK: MayAlias: i32* %b, i32* @g2
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; CHECK: NoAlias: i32* @g3, i32** %a
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; CHECK: MayAlias: i32* @g3, i32* select (i1 icmp ne (i32* @g, i32* null), i32* @g2, i32* @g3)
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; CHECK: MayAlias: i32* %b, i32* @g3
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; CHECK: MayAlias: i32* @g2, i32* @g3
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define void @foo() {
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entry:
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%a = alloca i32*, align 8
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store i32* select (i1 icmp ne (i32* @g, i32* null), i32* @g2, i32* @g3), i32** %a
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%b = load i32*, i32** %a
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%c = load i32, i32* %b
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%d = load i32, i32* @g2
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%e = load i32, i32* @g3
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ret void
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}
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