Arnold Schwaighofer 1bdb320dae BasicAA: Fix value equality and phi cycles
When there are cycles in the value graph we have to be careful interpreting
"Value*" identity as "value" equivalence. We interpret the value of a phi node
as the value of its operands.
When we check for value equivalence now we make sure that the "Value*" dominates
all cycles (phis).

%0 = phi [%noaliasval, %addr2]
%l = load %ptr
%addr1 = gep @a, 0, %l
%addr2 = gep @a, 0, (%l + 1)
store %ptr ...

Before this patch we would return NoAlias for (%0, %addr1) which is wrong
because the value of the load is from different iterations of the loop.

Tested on x86_64 -mavx at O3 and O3 -flto with no performance or compile time
regressions.

PR18068
radar://15653794

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198290 91177308-0d34-0410-b5e6-96231b3b80d8
2014-01-02 03:31:36 +00:00

15 lines
364 B
LLVM

; RUN: opt < %s -domtree -basicaa -globalsmodref-aa -gvn -S | FileCheck %s
@X = internal global i32 4 ; <i32*> [#uses=1]
define i32 @test(i32* %P) {
; CHECK: @test
; CHECK-NEXT: store i32 7, i32* %P
; CHECK-NEXT: store i32 12, i32* @X
; CHECK-NEXT: ret i32 7
store i32 7, i32* %P
store i32 12, i32* @X
%V = load i32* %P ; <i32> [#uses=1]
ret i32 %V
}