Improve Aliasing of operations to static alloca

Recommiting after adding check to avoid miscomputing alias information
on addresses of the same base but different subindices.

Memory accesses offset from frame indices may alias, e.g., we
may merge write from function arguments passed on the stack when they
are contiguous. As a result, when checking aliasing, we consider the
underlying frame index's offset from the stack pointer.

Static allocs are realized as stack objects in SelectionDAG, but its
offset is not set until post-DAG causing DAGCombiner's alias check to
consider access to static allocas to frequently alias. Modify isAlias
to consider access between static allocas and access from other frame
objects to be considered aliasing.

Many test changes are included here. Most are fixes for tests which
indirectly relied on our aliasing ability and needed to be modified to
preserve their original intent.

The remaining tests have minor improvements due to relaxed
ordering. The exception is CodeGen/X86/2011-10-19-widen_vselect.ll
which has a minor degradation dispite though the pre-legalized DAG is
improved.

Reviewers: rnk, mkuper, jonpa, hfinkel, uweigand

Reviewed By: rnk

Subscribers: sdardis, nemanjai, javed.absar, llvm-commits

Differential Revision: https://reviews.llvm.org/D33345

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@308025 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 2 insertions, 2 deletions

diff --git a/test/CodeGen/MSP430/vararg.ll b/test/CodeGen/MSP430/vararg.ll
index 4baf499848f..3501861f575 100644
--- a/test/CodeGen/MSP430/vararg.ll
+++ b/test/CodeGen/MSP430/vararg.ll
@@ -39,11 +39,11 @@ entry:
 ; CHECK-LABEL: va_copy:
   %vl.addr = alloca i8*, align 2
   %vl2 = alloca i8*, align 2
-; CHECK: mov.w r12, 2(r1)
+; CHECK-DAG: mov.w r12, 2(r1)
   store i8* %vl, i8** %vl.addr, align 2
   %0 = bitcast i8** %vl2 to i8*
   %1 = bitcast i8** %vl.addr to i8*
-; CHECK-NEXT: mov.w r12, 0(r1)
+; CHECK-DAG: mov.w r12, 0(r1)
   call void @llvm.va_copy(i8* %0, i8* %1)
   ret void
 }