<html>
<head>
<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 - Improve store merging"
href="https://bugs.llvm.org/show_bug.cgi?id=47023">47023</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Improve store merging
</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>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>Common Code Generator Code
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>david.bolvansky@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>struct data_t {
char data[16];
};
void process(data_t);
void process3(data_t, data_t, data_t);
void bad1() { process({1, 2, 3, 4, 5}); }
void bad2() { process({1, 2, 3, 4, 5, 1, 2, 3, 4, 5, 1, 2, 3, 4, 5}); }
void bad3() {
process3({1, 2, 3, 4, 5, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
{11, 12, 13, 14, 15, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10},
{21, 22, 23, 24, 25, 20, 20, 20, 10, 20, 20, 20, 20, 20, 20});
}
void bad4() {
process3({1, 2, 3, 4, 5, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
{11, 12, 13, 14, 15, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10},
{21, 22, 23, 24, 25, 20, 20, 20, 10, 20, 20, 20, 20, 20, 20, 11});
}
Clang:
bad1(): # @bad1()
sub rsp, 24
mov dword ptr [rsp + 8], 67305985
mov byte ptr [rsp + 12], 5
mov qword ptr [rsp + 13], 0
mov dword ptr [rsp + 20], 0
mov rdi, qword ptr [rsp + 8]
xor esi, esi
call process(data_t)
add rsp, 24
ret
.LCPI1_0:
.byte 1 # 0x1
.byte 2 # 0x2
.byte 3 # 0x3
.byte 4 # 0x4
.byte 5 # 0x5
.byte 1 # 0x1
.byte 2 # 0x2
.byte 3 # 0x3
.byte 4 # 0x4
.byte 5 # 0x5
.byte 1 # 0x1
.byte 2 # 0x2
.byte 3 # 0x3
.byte 4 # 0x4
.byte 5 # 0x5
.byte 0 # 0x0
bad2(): # @bad2()
sub rsp, 24
movaps xmm0, xmmword ptr [rip + .LCPI1_0] # xmm0 =
[1,2,3,4,5,1,2,3,4,5,1,2,3,4,5,0]
movaps xmmword ptr [rsp], xmm0
mov rdi, qword ptr [rsp]
mov rsi, qword ptr [rsp + 8]
call process(data_t)
add rsp, 24
ret
bad3(): # @bad3()
sub rsp, 24
movabs r8, 1446803478303675925
mov qword ptr [rsp + 8], r8
mov byte ptr [rsp + 16], 10
mov dword ptr [rsp + 17], 336860180
mov word ptr [rsp + 21], 5140
mov byte ptr [rsp + 23], 0
mov r9, qword ptr [rsp + 16]
movabs rdi, 21542142465
movabs rdx, 723401749922909195
movabs rcx, 723401728380766730
mov esi, 0
call process3(data_t, data_t, data_t)
add rsp, 24
ret
bad4(): # @bad4()
movabs rdi, 21542142465
movabs rdx, 723401749922909195
movabs rcx, 723401728380766730
movabs r8, 1446803478303675925
movabs r9, 798285110420182026
mov esi, 0
jmp process3(data_t, data_t, data_t)
GCC:
bad1():
movabs rdi, 21542142465
xor esi, esi
jmp process(data_t)
bad2():
mov rdi, QWORD PTR .LC0[rip]
movabs rsi, 1411785848587524
jmp process(data_t)
bad3():
mov r8, QWORD PTR .LC1[rip]
xor esi, esi
movabs r9, 5651576002974730
movabs rdx, 723401749922909195
movabs rcx, 723401728380766730
movabs rdi, 21542142465
jmp process3(data_t, data_t, data_t)
bad4():
movabs r8, 1446803478303675925
xor esi, esi
movabs r9, 798285110420182026
movabs rdx, 723401749922909195
movabs rcx, 723401728380766730
movabs rdi, 21542142465
jmp process3(data_t, data_t, data_t)
.LC0:
.byte 1
.byte 2
.byte 3
.byte 4
.byte 5
.byte 1
.byte 2
.byte 3
.LC1:
.byte 21
.byte 22
.byte 23
.byte 24
.byte 25
.byte 20
.byte 20
.byte 20
GCC's codegen is better here..
Godbolt: <a href="https://godbolt.org/z/xGY79q">https://godbolt.org/z/xGY79q</a></pre>
</div>
</p>
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