http://llvm.org/bugs/show_bug.cgi?id=18069
Bug ID: 18069
Summary: Arrays on stack are misaligned.
Product: tools
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P
Component: llc
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Classification: Unclassified
Created attachment 11615
--> http://llvm.org/bugs/attachment.cgi?id=11615&action=edit
main returns 0 if aligned correctly, 1 if not.
I am seeing an issue with an alloca on the stack that is requesting an
alignment, but the alignment is not being guaranteed when I compile with
-mtriple=i686-pc-linux and x86_64-pc-linux. If anything, it could be
misaligned:
main: # @main
# BB#0:
subl $44, %esp
movl $16, %eax
leal 16(%esp), %ecx
I tried i686-pc-windows and do not see an issue because the stack pointer is
realigned before calculating the array's address:
main: # @main
# BB#0:
pushl %ebp
movl %esp, %ebp
andl $-16, %esp
subl $48, %esp
movl $16, %eax
leal 16(%esp), %ecx
I am compiling the .ll file attached with llc -O0, however, the code I found
this problem in was compiled with -O2. I had two arrays on the stack and the
calculations for element positions relied on the alignment, thus there was data
corruption.
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