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Properly model precise lifetime when given an incomplete dataflow sequence.

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The normal dataflow sequence in the ARC optimizer consists of the following
states:

    Retain -> CanRelease -> Use -> Release

The optimizer before this patch stored the uses that determine the lifetime of
the retainable object pointer when it bottom up hits a retain or when top down
it hits a release. This is correct for an imprecise lifetime scenario since what
we are trying to do is remove retains/releases while making sure that no
``CanRelease'' (which is usually a call) deallocates the given pointer before we
get to the ``Use'' (since that would cause a segfault).

If we are considering the precise lifetime scenario though, this is not
correct. In such a situation, we *DO* care about the previous sequence, but
additionally, we wish to track the uses resulting from the following incomplete
sequences:

  Retain -> CanRelease -> Release   (TopDown)
  Retain <- Use <- Release          (BottomUp)

*NOTE* This patch looks large but the most of it consists of updating
test cases. Additionally this fix exposed an additional bug. I removed
the test case that expressed said bug and will recommit it with the fix
in a little bit.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@178921 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Michael Gottesman
2013-04-05 22:54:28 +00:00
parent 2e80991a77
commit e7ce2b3f75
4 changed files with 962 additions and 101 deletions
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51
test/Transforms/ObjCARC/intrinsic-use.ll
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@@ -34,7 +34,9 @@ declare void @test0_helper(i8*, i8**)
; CHECK-NEXT: @objc_release(i8* [[VAL1]])
; CHECK-NEXT: @objc_autorelease(i8* %x)
; CHECK-NEXT: store i8* %x, i8** %out
; CHECK-NEXT: @objc_retain(i8* %x)
; CHECK-NEXT: @objc_release(i8* [[VAL2]])
; CHECK-NEXT: @objc_release(i8* %x)
; CHECK-NEXT: ret void
define void @test0(i8** %out, i8* %x, i8* %y) {
entry:
@@ -61,3 +63,52 @@ entry:
call void @objc_release(i8* %x) nounwind
ret void
}
; CHECK: define void @test0a(
; CHECK: @objc_retain(i8* %x)
; CHECK-NEXT: store i8* %y, i8** %temp0
; CHECK-NEXT: @objc_retain(i8* %y)
; CHECK-NEXT: call void @test0_helper
; CHECK-NEXT: [[VAL1:%.*]] = load i8** %temp0
; CHECK-NEXT: call void (...)* @clang.arc.use(i8* %y)
; CHECK-NEXT: @objc_retain(i8* [[VAL1]])
; CHECK-NEXT: @objc_release(i8* %y)
; CHECK-NEXT: store i8* [[VAL1]], i8** %temp1
; CHECK-NEXT: call void @test0_helper
; CHECK-NEXT: [[VAL2:%.*]] = load i8** %temp1
; CHECK-NEXT: call void (...)* @clang.arc.use(i8* [[VAL1]])
; CHECK-NEXT: @objc_retain(i8* [[VAL2]])
; CHECK-NEXT: @objc_release(i8* [[VAL1]])
; CHECK-NEXT: @objc_autorelease(i8* %x)
; CHECK-NEXT: @objc_release(i8* [[VAL2]])
; CHECK-NEXT: store i8* %x, i8** %out
; CHECK-NEXT: ret void
define void @test0a(i8** %out, i8* %x, i8* %y) {
entry:
%temp0 = alloca i8*, align 8
%temp1 = alloca i8*, align 8
%0 = call i8* @objc_retain(i8* %x) nounwind
%1 = call i8* @objc_retain(i8* %y) nounwind
store i8* %y, i8** %temp0
call void @test0_helper(i8* %x, i8** %temp0)
%val1 = load i8** %temp0
%2 = call i8* @objc_retain(i8* %val1) nounwind
call void (...)* @clang.arc.use(i8* %y) nounwind
call void @objc_release(i8* %y) nounwind, !clang.imprecise_release !0
store i8* %val1, i8** %temp1
call void @test0_helper(i8* %x, i8** %temp1)
%val2 = load i8** %temp1
%3 = call i8* @objc_retain(i8* %val2) nounwind
call void (...)* @clang.arc.use(i8* %val1) nounwind
call void @objc_release(i8* %val1) nounwind, !clang.imprecise_release !0
%4 = call i8* @objc_retain(i8* %x) nounwind
%5 = call i8* @objc_autorelease(i8* %x) nounwind
store i8* %x, i8** %out
call void @objc_release(i8* %val2) nounwind, !clang.imprecise_release !0
call void @objc_release(i8* %x) nounwind, !clang.imprecise_release !0
ret void
}
!0 = metadata !{}