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When folding a load from a global constant, if the load started in the middle 

of an array element (rather than at the beginning of the element) and extended
into the next element, then the load from the second element was being handled
wrong due to incorrect updating of the notion of which byte to load next.  This
fixes PR13442.  Thanks to Chris Smowton for reporting the problem, analyzing it
and providing a fix.

llvm-svn: 160711
This commit is contained in:
Duncan Sands 2012-07-25 09:14:54 +00:00
parent ff7ff3f30b
commit 0b875a0c29
2 changed files with 20 additions and 5 deletions
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13
llvm/lib/Analysis/ConstantFolding.cpp
View File

@ -358,17 +358,20 @@ static bool ReadDataFromGlobal(Constant *C, uint64_t ByteOffset,
NumElts = AT->getNumElements();
else
NumElts = cast<VectorType>(C->getType())->getNumElements();
for (; Index != NumElts; ++Index) {
if (!ReadDataFromGlobal(C->getAggregateElement(Index), Offset, CurPtr,
BytesLeft, TD))
return false;
if (EltSize >= BytesLeft)
uint64_t BytesWritten = EltSize - Offset;
assert(BytesWritten <= EltSize && "Not indexing into this element?");
if (BytesWritten >= BytesLeft)
return true;
Offset = 0;
BytesLeft -= EltSize;
CurPtr += EltSize;
BytesLeft -= BytesWritten;
CurPtr += BytesWritten;
}
return true;
}

12
llvm/test/Transforms/InstCombine/2012-07-25-LoadPart.ll Normal file
View File

@ -0,0 +1,12 @@
; RUN: opt < %s -instcombine -S | FileCheck %s
; PR13442
target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:32:32-n8:16:32-S128"
@test = constant [4 x i32] [i32 1, i32 2, i32 3, i32 4]
define i64 @foo() {
%ret = load i64* bitcast (i8* getelementptr (i8* bitcast ([4 x i32]* @test to i8*), i64 2) to i64*)
ret i64 %ret
; CHECK: ret i64 844424930263040
}