https://llvm.org/bugs/show_bug.cgi?id=26627
Bug ID: 26627
Summary: constant folding with ctype functions
Product: clang
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P
Component: LLVM Codegen
Assignee: unassignedclangb...@nondot.org
Reporter: helloqi...@gmail.com
CC: llvm-bugs@lists.llvm.org
Classification: Unclassified
It appears that clang does not support constant folding with ctype functions at
-O3.
$ clang-trunk -v
clang version 3.9.0 (trunk 260880) (llvm/trunk 260879)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/local/bin
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/4.9
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/4.9.3
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/5.3.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4.7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8.5
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.9.3
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.3.0
Found candidate GCC installation:
/usr/local/bin/../lib/gcc/x86_64-unknown-linux-gnu/5.3.0
Selected GCC installation:
/usr/local/bin/../lib/gcc/x86_64-unknown-linux-gnu/5.3.0
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Selected multilib: .;@m64
$ clang-trunk -O3 abc.c
abc.c:3:7: warning: implicit declaration of function 'toupper' is invalid in
C99 [-Wimplicit-function-declaration]
if (toupper(i) != toupper(i)) link_failure_();
^
abc.c:3:33: warning: implicit declaration of function 'link_failure_' is
invalid in C99 [-Wimplicit-function-declaration]
if (toupper(i) != toupper(i)) link_failure_();
^
2 warnings generated.
/tmp/abc-a497fe.o: In function `fn1':
abc.c:(.text+0x25): undefined reference to `link_failure_'
clang-3.9: error: linker command failed with exit code 1 (use -v to see
invocation)
$ cat abc.c
void fn1() {
int i=1;
if (toupper(i) != toupper(i)) link_failure_();
}
int main() {}
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