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<base href="https://bugs.llvm.org/">
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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 - dead function call is not removed in branch comparing global variable addresses"
href="https://bugs.llvm.org/show_bug.cgi?id=49434">49434</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>dead function call is not removed in branch comparing global variable addresses
</td>
</tr>
<tr>
<th>Product</th>
<td>tools
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>Linux
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>opt
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>theodoridisgr@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>~/llvm-project/build/bin/clang -v
clang version 13.0.0 (<a href="https://github.com/llvm/llvm-project.git">https://github.com/llvm/llvm-project.git</a>
d2000b45d033c06dc7973f59909a0ad12887ff51)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/theo/llvm-project/build/bin
Found candidate GCC installation: /usr/lib/gcc/x86_64-pc-linux-gnu/10.2.0
Found candidate GCC installation: /usr/lib64/gcc/x86_64-pc-linux-gnu/10.2.0
Selected GCC installation: /usr/lib64/gcc/x86_64-pc-linux-gnu/10.2.0
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Selected multilib: .;@m64
Found CUDA installation: /opt/cuda, version 11.2
--------------------------------------------------------------------------------
cat test.c
char a, b[2];
extern void foo (void);
int main() {
char *c = &a, *d = &b[1];
if (c == d)
foo();
return 0;
}
--------------------------------------------------------------------------------
~/llvm-project/build/bin/clang -O3 -S -o /dev/stdout test.c
.text
.file "test.c"
.globl main # -- Begin function main
.p2align 4, 0x90
.type main,@function
main: # @main
.cfi_startproc
# %bb.0: # %entry
movl $b+1, %eax
cmpq $a, %rax
jne .LBB0_2
# %bb.1: # %if.then
pushq %rax
.cfi_def_cfa_offset 16
callq foo
addq $8, %rsp
.cfi_def_cfa_offset 8
.LBB0_2: # %if.end
xorl %eax, %eax
retq
.Lfunc_end0:
.size main, .Lfunc_end0-main
.cfi_endproc
# -- End function
.type a,@object # @a
.bss
.globl a
a:
.byte 0 # 0x0
.size a, 1
.type b,@object # @b
.globl b
b:
.zero 2
.size b, 2
.ident "clang version 13.0.0 (<a href="https://github.com/llvm/llvm-project.git">https://github.com/llvm/llvm-project.git</a>
d2000b45d033c06dc7973f59909a0ad12887ff51)"
.section ".note.GNU-stack","",@progbits
.addrsig
.addrsig_sym a
.addrsig_sym b
--------------------------------------------------------------------------------
if *d = &b[1]; is replaced with *d=b, the dead branch is properly DCE'd.</pre>
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