llvm/test/Transforms/GVN/pr17732.ll
David Majnemer 0ab2058852 IR: Do not canonicalize constant GEPs into an out-of-bounds array access
Summary:
Consider a GEP of:
i8* getelementptr ({ [2 x i8], i32, i8, [3 x i8] }* @main.c, i32 0, i32 0, i64 0)

If we proceeded to GEP the aforementioned object by 8, would form a GEP of:
i8* getelementptr ({ [2 x i8], i32, i8, [3 x i8] }* @main.c, i32 0, i32 0, i64 8)

Note that we would go through the first array member, causing an
out-of-bounds accesses.  This is problematic because we might get fooled
if we are trying to evaluate loads using this GEP, for example, based
off of an object with a constant initializer where the array is zero.

This fixes PR17732.

Reviewers: nicholas, chandlerc, void

Reviewed By: void

CC: llvm-commits, echristo, void, aemerson

Differential Revision: http://llvm-reviews.chandlerc.com/D2093

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@194220 91177308-0d34-0410-b5e6-96231b3b80d8
2013-11-07 22:15:53 +00:00

31 lines
1.8 KiB
LLVM

; RUN: opt -gvn -S -o - < %s | FileCheck %s
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"
%struct.with_array = type { [2 x i8], i32, i8 }
%struct.with_vector = type { <2 x i8>, i32, i8 }
@main.obj_with_array = private unnamed_addr constant { [2 x i8], i32, i8, [3 x i8] } { [2 x i8] zeroinitializer, i32 0, i8 1, [3 x i8] undef }, align 4
@array_with_zeroinit = common global %struct.with_array zeroinitializer, align 4
@main.obj_with_vector = private unnamed_addr constant { <2 x i8>, i32, i8, [3 x i8] } { <2 x i8> zeroinitializer, i32 0, i8 1, [3 x i8] undef }, align 4
@vector_with_zeroinit = common global %struct.with_vector zeroinitializer, align 4
define i32 @main() {
entry:
tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* getelementptr inbounds (%struct.with_array* @array_with_zeroinit, i64 0, i32 0, i64 0), i8* getelementptr inbounds ({ [2 x i8], i32, i8, [3 x i8] }* @main.obj_with_array, i64 0, i32 0, i64 0), i64 12, i32 4, i1 false)
%0 = load i8* getelementptr inbounds (%struct.with_array* @array_with_zeroinit, i64 0, i32 2), align 4
tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* getelementptr inbounds (%struct.with_vector* @vector_with_zeroinit, i64 0, i32 0, i64 0), i8* getelementptr inbounds ({ <2 x i8>, i32, i8, [3 x i8] }* @main.obj_with_vector, i64 0, i32 0, i64 0), i64 12, i32 4, i1 false)
%1 = load i8* getelementptr inbounds (%struct.with_vector* @vector_with_zeroinit, i64 0, i32 2), align 4
%conv0 = sext i8 %0 to i32
%conv1 = sext i8 %1 to i32
%and = and i32 %conv0, %conv1
ret i32 %and
; CHECK-LABEL: define i32 @main(
; CHECK: ret i32 1
}
declare void @llvm.memcpy.p0i8.p0i8.i64(i8* nocapture, i8* nocapture readonly, i64, i32, i1)