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[GlobalsAA] Partially back out r248576
See PR25822 for a more full summary, but we were conflating the concepts of "capture" and "escape". We were proving nocapture and using that proof to infer noescape, which is not true. Escaped-ness is a function-local property - as soon as a value is used in a call argument it escapes. Capturedness is a related but distinct property. It implies a *temporally limited* escape. Consider: static int a; int b; int g(int * nocapture arg); int f() { a = 2; // Even though a escapes to g, it is not captured so can be treated as non-escaping here. g(&a); // But here it must be treated as escaping. g(&b); // Now that g(&a) has returned we know it was not captured so we can treat it as non-escaping again. } The original commit did not sufficiently understand this nuance and so caused PR25822 and PR26046. r248576 included both a performance improvement (which has been backed out) and a related conformance fix (which has been kept along with its testcase). git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@257058 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -358,21 +358,6 @@ bool GlobalsAAResult::AnalyzeUsesOfPointer(Value *V,
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if (CS.isArgOperand(&U) && isFreeCall(I, &TLI)) {
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if (CS.isArgOperand(&U) && isFreeCall(I, &TLI)) {
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if (Writers)
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if (Writers)
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Writers->insert(CS->getParent()->getParent());
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Writers->insert(CS->getParent()->getParent());
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} else if (CS.doesNotCapture(CS.getDataOperandNo(&U))) {
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Function *ParentF = CS->getParent()->getParent();
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// A nocapture argument may be read from or written to, but does not
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// escape unless the call can somehow recurse.
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//
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// nocapture "indicates that the callee does not make any copies of
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// the pointer that outlive itself". Therefore if we directly or
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// indirectly recurse, we must treat the pointer as escaping.
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if (FunctionToSCCMap[ParentF] ==
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FunctionToSCCMap[CS.getCalledFunction()])
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return true;
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if (Readers)
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Readers->insert(ParentF);
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if (Writers)
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Writers->insert(ParentF);
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} else {
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} else {
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return true; // Argument of an unknown call.
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return true; // Argument of an unknown call.
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}
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}
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@ -1,57 +0,0 @@
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; RUN: opt < %s -globals-aa -aa-eval -print-all-alias-modref-info -disable-output 2>&1 | FileCheck %s
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target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
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target triple = "x86_64-apple-macosx10.10.0"
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@a = internal global i32 0, align 4
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@b = internal global i32 0, align 4
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define void @g(i32* %p, void (i32*)* nocapture %ptr) {
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entry:
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tail call void %ptr(i32* %p) #1
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ret void
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}
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; CHECK-LABEL: Function: f
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; CHECK: MayAlias: i32* %p, i32* @a
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; CHECK: MayAlias: i32* %q, i32* @a
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define i32 @f(i32 %n, i32* nocapture readonly %p, i32* nocapture %q, void (i32*)* nocapture %ptr) {
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entry:
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tail call void @g(i32* nonnull @a, void (i32*)* %ptr)
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%arrayidx = getelementptr inbounds i32, i32* %p, i64 0
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%z1 = load i32, i32* %arrayidx, align 4
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%z2 = load i32, i32* %q, align 4
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%add = add nsw i32 %z2, %z1
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store i32 %add, i32* %q, align 4
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ret i32 4
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}
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define void @g2(i32* nocapture %p, void (i32*)* nocapture %ptr) {
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entry:
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tail call void %ptr(i32* %p) #1
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ret void
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}
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; CHECK-LABEL: Function: f2
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; CHECK: NoAlias: i32* %p, i32* @b
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; CHECK: NoAlias: i32* %q, i32* @b
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define i32 @f2(i32 %n, i32* nocapture readonly %p, i32* nocapture %q, void (i32*)* nocapture %ptr) {
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entry:
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tail call void @g2(i32* nonnull @b, void (i32*)* %ptr)
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%arrayidx = getelementptr inbounds i32, i32* %p, i64 0
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%z1 = load i32, i32* %arrayidx, align 4
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%z2 = load i32, i32* %q, align 4
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%add = add nsw i32 %z2, %z1
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store i32 %add, i32* %q, align 4
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ret i32 4
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}
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declare void @g3()
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; CHECK-LABEL: Function: f3
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; CHECK: NoAlias: i32* %p, i32* @b
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define void @f3(i32* nocapture readonly %p) {
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entry:
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tail call void @g3() [ "deopt"(i32* @b, i32 *%p) ]
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unreachable
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}
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