RPCS3/llvm-mirror
1
0
Fork 0
mirror of https://github.com/RPCS3/llvm-mirror.git synced 2024-12-15 07:39:31 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

Don't assume that external global variables are aligned at their preferred

Browse Source 
alignment. Only the minimum alignment guaranteed by the ABI may be assumed.

llvm-svn: 78668
This commit is contained in:
Dan Gohman 2009-08-11 15:50:03 +00:00
parent cea903237c
commit 08e747855c
2 changed files with 32 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
lib/Analysis/ValueTracking.cpp
View File

@ -81,8 +81,16 @@ void llvm::ComputeMaskedBits(Value *V, const APInt &Mask,
// The address of an aligned GlobalValue has trailing zeros.
if (GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
unsigned Align = GV->getAlignment();
if (Align == 0 && TD && GV->getType()->getElementType()->isSized())
Align = TD->getPrefTypeAlignment(GV->getType()->getElementType());
if (Align == 0 && TD && GV->getType()->getElementType()->isSized()) {
const Type *ObjectType = GV->getType()->getElementType();
// If the object is defined in the current Module, we'll be giving
// it the preferred alignment. Otherwise, we have to assume that it
// may only have the minimum ABI alignment.
if (!GV->isDeclaration() && !GV->mayBeOverridden())
Align = TD->getPrefTypeAlignment(ObjectType);
else
Align = TD->getABITypeAlignment(ObjectType);
}
if (Align > 0)
KnownZero = Mask & APInt::getLowBitsSet(BitWidth,
CountTrailingZeros_32(Align));

22
test/Transforms/InstCombine/align-external.ll Normal file
View File

@ -0,0 +1,22 @@
; RUN: llvm-as < %s | opt -instcombine | llvm-dis | FileCheck %s
; Don't assume that external global variables have their preferred
; alignment. They may only have the ABI minimum alignment.
; CHECK: %s = shl i64 %a, 3
; CHECK: %r = or i64 %s, ptrtoint (i32* @A to i64)
; CHECK: %q = add i64 %r, 1
; CHECK: ret i64 %q
target datalayout = "-i32:8:32"
@A = external global i32
@B = external global i32
define i64 @foo(i64 %a) {
%t = ptrtoint i32* @A to i64
%s = shl i64 %a, 3
%r = or i64 %t, %s
%q = add i64 %r, 1
ret i64 %q
}