http://llvm.org/bugs/show_bug.cgi?id=16058
Bug ID: 16058
Summary: incorrect loop optimization at -O3
Product: clang
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P
Component: LLVM Codegen
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Classification: Unclassified
The following testcase is miscompiled by clang trunk at -O3 optimization level
on x86_64-linux-gnu, producing an executable that hangs. This occurs in both
32-bit and 64-bit mode.
$ clang-trunk -v
clang version 3.4 (trunk 182084)
Target: x86_64-pc-linux-gnu
Thread model: posix
$ clang-trunk -O2 hang.c
$ ./a.out
$ clang-trunk -O3 hang.c
$ ./a.out
<hangs>
--------------------------------
int a, b, c, *p = &a;
static void
foo(int *l)
{
for (b = -28; b < 4; b++)
{
*l = 1;
for (c = 0; c; --c)
*l = 0;
}
label:
for (b = 0; b >= 0; --b)
{
if (*p)
continue;
goto label;
}
return;
}
int
main()
{
int *q = &a;
foo(q);
return 0;
}
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