llvm/test/Transforms/Util/MemorySSA/constant-memory.ll
George Burgess IV 94c82b281d [MSSA] Add logic for special handling of atomics/volatiles.
This patch makes MemorySSA recognize atomic/volatile loads, and makes
MSSA treat said loads specially. This allows us to be a bit more
aggressive in some cases.

Administrative note: Revision was LGTM'ed by reames in person.
Additionally, this doesn't include the `invariant.load` recognition in
the differential revision, because I feel it's better to commit that
separately. Will commit soon.

Differential Revision: https://reviews.llvm.org/D16875


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@277637 91177308-0d34-0410-b5e6-96231b3b80d8
2016-08-03 19:39:54 +00:00

42 lines
1.2 KiB
LLVM

; RUN: opt -basicaa -print-memoryssa -verify-memoryssa -analyze < %s 2>&1 | FileCheck %s
;
; Things that BasicAA can prove points to constant memory should be
; liveOnEntry, as well.
declare void @clobberAllTheThings()
@str = private unnamed_addr constant [2 x i8] c"hi"
define i8 @foo() {
; CHECK: 1 = MemoryDef(liveOnEntry)
; CHECK-NEXT: call void @clobberAllTheThings()
call void @clobberAllTheThings()
%1 = getelementptr [2 x i8], [2 x i8]* @str, i64 0, i64 0
; CHECK: MemoryUse(liveOnEntry)
; CHECK-NEXT: %2 = load i8
%2 = load i8, i8* %1, align 1
%3 = getelementptr [2 x i8], [2 x i8]* @str, i64 0, i64 1
; CHECK: MemoryUse(liveOnEntry)
; CHECK-NEXT: %4 = load i8
%4 = load i8, i8* %3, align 1
%5 = add i8 %2, %4
ret i8 %5
}
define i8 @select(i1 %b) {
%1 = alloca i8, align 1
; CHECK: 1 = MemoryDef(liveOnEntry)
; CHECK-NEXT: store i8 0
store i8 0, i8* %1, align 1
; CHECK: 2 = MemoryDef(1)
; CHECK-NEXT: call void @clobberAllTheThings()
call void @clobberAllTheThings()
%2 = getelementptr [2 x i8], [2 x i8]* @str, i64 0, i64 0
%3 = select i1 %b, i8* %2, i8* %1
; CHECK: MemoryUse(2)
; CHECK-NEXT: %4 = load i8
%4 = load i8, i8* %3, align 1
ret i8 %4
}