http://llvm.org/bugs/show_bug.cgi?id=17882
Bug ID: 17882
Summary: missed dead code elimination, linker error
Product: clang
Version: 3.3
Hardware: PC
OS: FreeBSD
Status: NEW
Severity: normal
Priority: P
Component: -New Bugs
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Classification: Unclassified
The below test case fails to link with clang. gcc48 does work.
-----
extern void dead(void);
void test(int x)
{
if (x || 1)
return;
dead();
}
int main()
{
test(0);
return 0;
}
-----
When I change the if (x||1) to if(1||x) the compile/link succeeds.
Here the output of the failing test:
[tcx58:~] andreast% clang -o dead dead.c
/tmp/dead-hllbPY.o: In function `test':
dead.c:(.text+0x2d): undefined reference to `dead'
clang: error: linker command failed with exit code 1 (use -v to see invocation)
The original code was discovered in qemu-trunk, the workaround is to change the
if condition.
The credit for the test case and the workaround goes to Paolo Bonzini.
I have tested this on FreeBSD -CURRENT:
[tcx58:~] andreast% clang -v
FreeBSD clang version 3.3 (tags/RELEASE_33/final 183502) 20130610
Target: x86_64-unknown-freebsd11.0
Thread model: posix
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