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<base href="https://llvm.org/bugs/" />
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<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Possible miscompile with arm64"
href="https://llvm.org/bugs/show_bug.cgi?id=23437">23437</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Possible miscompile with arm64
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>All
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>Backend: AArch64
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>nicolasweber@gmx.de
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>This assert fails when building with trunk clang when targeting arm64:
$ cat test.cc
#include <assert.h>
int main(int argc, char **argv) {
const struct {
const char* to_escape;
const char* escaped;
} cases[] = {
{"\xe5\xc4\x4f\x05\xb6\xfd\0", "\\u00E5\\u00C4O\\u0005\\u00B6\\u00FD"},
};
assert((unsigned char)cases[0].to_escape[0] == 0xe5);
return 0;
}
$ Release+Asserts/bin/clang++ -isysroot
/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS8.2.sdk
-O0 -gdwarf-2 -fvisibility=hidden -miphoneos-version-min=7.0 -arch arm64
-std=c++11 -stdlib=libc++ -fno-rtti -fno-exceptions -fvisibility-inlines-hidden
-fno-threadsafe-statics -fcolor-diagnostics -fstack-protector-all -c test.cc
-o test.o
$ Release+Asserts/bin/clang++ -Wl,-search_paths_first -Wl,-ObjC
-miphoneos-version-min=7.0 -isysroot
/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS8.2.sdk
-arch arm64 -L. -stdlib=libc++ -o foo test.o
Here's the disassembly of the relevant bits of main:
0000000100007e60 stp x29, x30, [sp, #0xfffffff0]!
; XREF=0x1000000d0
0000000100007e64 mov x29, sp
0000000100007e68 sub sp, sp, #0x20
0000000100007e6c adrp x8, #0x100008000
; imp___got____stack_chk_guard
0000000100007e70 add x8, x8, #0x28
; __ZZ4mainE5cases
0000000100007e74 adrp x10, #0x100008000
; imp___got____stack_chk_guard
0000000100007e78 ldr x10, [x10]
0000000100007e7c ldr x10, [x10]
0000000100007e80 mov x2, x10
0000000100007e84 stur x10, [x29, #0xfffffff8]
0000000100007e88 stur wzr, [x29, #0xfffffff4]
0000000100007e8c str w0, [sp, #0x10]
0000000100007e90 str x1, [sp, #0x8]
0000000100007e94 ldr x8, [x8]
0000000100007e98 ldrb w0, [x8]
0000000100007e9c cmp w0, #0xe5
0000000100007ea0 cset w0, eq
0000000100007ea4 eor w0, w0, #0x1
0000000100007ea8 cmp w0, #0x0
0000000100007eac str x2, [sp]
0000000100007eb0 b.eq 0x100007ed4
0000000100007eb4 adrp x8, #0x100007000
; 0x100007000 (__mh_execute_header + 0x7000)
0000000100007eb8 add x0, x8, #0xf78
; "main"
0000000100007ebc adrp x8, #0x100007000
; 0x100007000 (__mh_execute_header + 0x7000)
0000000100007ec0 add x1, x8, #0xf7d
; "test.cc"
0000000100007ec4 orr w2, wzr, #0x10
0000000100007ec8 adrp x8, #0x100007000
; 0x100007000 (__mh_execute_header + 0x7000), argument #1 for method
imp___stubs____assert_rtn
0000000100007ecc add x3, x8, #0xf85
; "(unsigned char)cases[0].to_escape[0] == 0xe5"
0000000100007ed0 bl imp___stubs____assert_rtn
I can't read arm64 well enough to say if that makes sense.
The assert doesn't fire with xcode's clang, so maybe it's a somewhat recent
regression?</pre>
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