6502/llvm-6502
1
0
Fork 0
mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2024-07-08 18:30:04 +00:00
Code Issues Projects Releases Wiki Activity

BasicAA: We need to check both access sizes when comparing a gep and an

Browse Source 
underlying object of unknown size.

Fixes PR18460.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@199351 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Arnold Schwaighofer 2014-01-16 04:53:18 +00:00
parent 59c2fe1af1
commit 8963071a14
2 changed files with 42 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
lib/Analysis/BasicAliasAnalysis.cpp
View File

@ -1009,7 +1009,15 @@ BasicAliasAnalysis::aliasGEP(const GEPOperator *GEP1, uint64_t V1Size,
return NoAlias;
}
} else {
if (V1Size != UnknownSize) {
// We have the situation where:
// + +
// | BaseOffset |
// ---------------->|
// |-->V1Size |-------> V2Size
// GEP1 V2
// We need to know that V2Size is not unknown, otherwise we might have
// stripped a gep with negative index ('gep <ptr>, -1, ...).
if (V1Size != UnknownSize && V2Size != UnknownSize) {
if (-(uint64_t)GEP1BaseOffset < V1Size)
return PartialAlias;
return NoAlias;

33
test/Analysis/BasicAA/noalias-bugs.ll Normal file
View File

@ -0,0 +1,33 @@
; RUN: opt -S -basicaa -dse < %s | FileCheck %s
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"
; We incorrectly returned noalias in the example below for "ptr.64" and
; "either_ptr.64".
; PR18460
%nested = type { %nested.i64 }
%nested.i64 = type { i64 }
define i64 @testcase(%nested * noalias %p1, %nested * noalias %p2,
i32 %a, i32 %b) {
%ptr = getelementptr inbounds %nested* %p1, i64 -1, i32 0
%ptr.64 = getelementptr inbounds %nested.i64* %ptr, i64 0, i32 0
%ptr2= getelementptr inbounds %nested* %p2, i64 0, i32 0
%cmp = icmp ult i32 %a, %b
%either_ptr = select i1 %cmp, %nested.i64* %ptr2, %nested.i64* %ptr
%either_ptr.64 = getelementptr inbounds %nested.i64* %either_ptr, i64 0, i32 0
; Because either_ptr.64 and ptr.64 can alias (we used to return noalias)
; elimination of the first store is not valid.
; CHECK: store i64 2
; CHECK: load
; CHECK; store i64 1
store i64 2, i64* %ptr.64, align 8
%r = load i64* %either_ptr.64, align 8
store i64 1, i64* %ptr.64, align 8
ret i64 %r
}