https://llvm.org/bugs/show_bug.cgi?id=27833
Bug ID: 27833
Summary: SIMD code with -O2
Product: clang
Version: unspecified
Hardware: PC
OS: MacOS X
Status: NEW
Severity: normal
Priority: P
Component: -New Bugs
Assignee: unassignedclangb...@nondot.org
Reporter: kazunori.ueda...@gmail.com
CC: llvm-bugs@lists.llvm.org
Classification: Unclassified
Created attachment 16396
--> https://llvm.org/bugs/attachment.cgi?id=16396&action=edit
v2d2.i and related source files
The enclosed program, compiled with clang -m32 -O2 *.i, produces a strange
output
0x7b06e5ed, 0x7b06e44f, 0x7b06e5f5, 0x7b06e42f
0x7b06e5f5, 0x7b06e42f, 0x0, 0x0
segmentation fault: 11
from two successive printf statements in v2d2.i:
printf("%p, %p, %p, %p\n",
allocp[116], allocp[117], allocp[118], allocp[119]);
x59 = ((q)((unsigned long)(&allocp[118]) + 0x1));
printf("%p, %p, %p, %p\n",
allocp[116], allocp[117], allocp[118], allocp[119]);
while clang -m32 -O1 *.i produces an expected output
0x7c2d81ed, 0x7c2d804f, 0x7c2d81f5, 0x7c2d802f
0x7c2d81ed, 0x7c2d804f, 0x7c2d81f5, 0x7c2d802f
I look into the assembly code of v2d2.c and found that -O2 uses SIMD
instructions while -O1 doesn't.
FYI, v2d2.c is a simplified version of a machine-generated program from our
compiler, and all the other .c files are just to make v2d2.c run.
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