Merging r198290:

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r198290 | aschwaighofer | 2014-01-01 22:31:36 -0500 (Wed, 01 Jan 2014) | 23 lines

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

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_34@206051 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 54 insertions, 0 deletions

diff --git a/test/Analysis/BasicAA/phi-aa.ll b/test/Analysis/BasicAA/phi-aa.ll
index 6aa26c185e..ed2d23e3ad 100644
--- a/test/Analysis/BasicAA/phi-aa.ll
+++ b/test/Analysis/BasicAA/phi-aa.ll
@@ -1,12 +1,20 @@
 ; RUN: opt < %s -basicaa -aa-eval -print-all-alias-modref-info -disable-output 2>&1 | FileCheck %s
+; RUN: opt < %s -domtree -basicaa -aa-eval -print-all-alias-modref-info -disable-output 2>&1 | FileCheck %s --check-prefix=DOM
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
 ; rdar://7282591
 
 @X = common global i32 0
 @Y = common global i32 0
 @Z = common global i32 0
 
+; CHECK-LABEL: foo
 ; CHECK:  NoAlias: i32* %P, i32* @Z
 
+; DOM-LABEL: foo
+; DOM:  NoAlias: i32* %P, i32* @Z
+
 define void @foo(i32 %cond) nounwind {
 entry:
   %"alloca point" = bitcast i32 0 to i32
@@ -29,3 +37,49 @@ bb2:
 return:
   ret void
 }
+
+; Pointers can vary in between iterations of loops.
+; PR18068
+
+; CHECK-LABEL: pr18068
+; CHECK: MayAlias: i32* %0, i32* %arrayidx5
+
+; DOM-LABEL: pr18068
+; DOM: MayAlias: i32* %0, i32* %arrayidx5
+
+define i32 @pr18068(i32* %jj7, i32* %j) {
+entry:
+  %oa5 = alloca [100 x i32], align 16
+  br label %codeRepl
+
+codeRepl:
+  %0 = phi i32* [ %arrayidx13, %for.body ], [ %j, %entry ]
+  %targetBlock = call i1 @cond(i32* %jj7)
+  br i1 %targetBlock, label %for.body, label %bye
+
+for.body:
+  %1 = load i32* %jj7, align 4
+  %idxprom4 = zext i32 %1 to i64
+  %arrayidx5 = getelementptr inbounds [100 x i32]* %oa5, i64 0, i64 %idxprom4
+  %2 = load i32* %arrayidx5, align 4
+  %sub6 = sub i32 %2, 6
+  store i32 %sub6, i32* %arrayidx5, align 4
+  ; %0 and %arrayidx5 can alias! It is not safe to DSE the above store.
+  %3 = load i32* %0, align 4
+  store i32 %3, i32* %arrayidx5, align 4
+  %sub11 = add i32 %1, -1
+  %idxprom12 = zext i32 %sub11 to i64
+  %arrayidx13 = getelementptr inbounds [100 x i32]* %oa5, i64 0, i64 %idxprom12
+  call void @inc(i32* %jj7)
+  br label %codeRepl
+
+bye:
+  %.reload = load i32* %jj7, align 4
+  ret i32 %.reload
+}
+
+declare i1 @cond(i32*)
+
+declare void @inc(i32*)
+
+