49cad7d70b
Prior to this patch, the MemorySSA caching visitor would cache all
calls that it visited. When paired with phi optimization, this can be
problematic. Consider:
define void @foo() {
; 1 = MemoryDef(liveOnEntry)
call void @clobberFunction()
br i1 undef, label %if.end, label %if.then
if.then:
; MemoryUse(??)
call void @readOnlyFunction()
; 2 = MemoryDef(1)
call void @clobberFunction()
br label %if.end
if.end:
; 3 = MemoryPhi(...)
; MemoryUse(?)
call void @readOnlyFunction()
ret void
}
When optimizing MemoryUse(?), we visit defs 1 and 2, so we note to
cache them later. We ultimately end up not being able to optimize
passed the Phi, so we set MemoryUse(?) to point to the Phi. We then
cache the clobbering call for def 1 to be the Phi.
This commit changes this behavior so that we wipe out any calls
added to VisistedCalls while visiting the defs of a phi we couldn't
optimize.
Aside: With this patch, we now can bootstrap clang/LLVM without a
single MemorySSA verifier failure. Woohoo. :)
llvm-svn: 264820
54 lines
1.3 KiB
LLVM
54 lines
1.3 KiB
LLVM
; RUN: opt -basicaa -print-memoryssa -verify-memoryssa -analyze < %s 2>&1 | FileCheck %s
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;
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; Ensuring that external functions without attributes are MemoryDefs
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@g = external global i32
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declare void @modifyG()
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define i32 @foo() {
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; CHECK: MemoryUse(liveOnEntry)
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; CHECK-NEXT: %1 = load i32
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%1 = load i32, i32* @g
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; CHECK: 1 = MemoryDef(liveOnEntry)
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; CHECK-NEXT: store i32 4
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store i32 4, i32* @g, align 4
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; CHECK: 2 = MemoryDef(1)
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; CHECK-NEXT: call void @modifyG()
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call void @modifyG()
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; CHECK: MemoryUse(2)
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; CHECK-NEXT: %2 = load i32
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%2 = load i32, i32* @g
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%3 = add i32 %2, %1
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ret i32 %3
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}
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declare void @readEverything() readonly
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declare void @clobberEverything()
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; CHECK-LABEL: define void @bar
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define void @bar() {
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; CHECK: 1 = MemoryDef(liveOnEntry)
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; CHECK-NEXT: call void @clobberEverything()
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call void @clobberEverything()
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br i1 undef, label %if.end, label %if.then
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if.then:
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; CHECK: MemoryUse(1)
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; CHECK-NEXT: call void @readEverything()
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call void @readEverything()
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; CHECK: 2 = MemoryDef(1)
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; CHECK-NEXT: call void @clobberEverything()
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call void @clobberEverything()
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br label %if.end
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if.end:
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; CHECK: 3 = MemoryPhi({%0,1},{if.then,2})
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; CHECK: MemoryUse(3)
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; CHECK-NEXT: call void @readEverything()
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call void @readEverything()
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ret void
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}
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