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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 - Regression: Needless memcpy call"
href="https://bugs.llvm.org/show_bug.cgi?id=38020">38020</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Regression: Needless memcpy call
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>unspecified
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>All
</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>LLVM Codegen
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>nicolasweber@gmx.de
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>$ cat repro.ii
typedef unsigned long DWORD;
typedef void *HANDLE;
__declspec(dllimport) HANDLE GetStdHandle(DWORD);
void mainCRTStartup(void) {
const char msg[] = "012345678901234567890123456789";
HANDLE out = GetStdHandle(((DWORD)-11));
WriteFile(out, msg, sizeof(msg), (DWORD[]){0}, ((void *)0));
}
$ ~/src/chrome/src/third_party/llvm-build/Release+Asserts/bin/clang "-cc1"
"-triple" "i386-pc-windows-msvc19.11.0" "-S" "-O2" -fms-extensions "-o" - "-x"
"c" "repro.ii"
repro.ii:7:3: warning: implicit declaration of function 'WriteFile' is invalid
in C99
WriteFile(out, msg, sizeof(msg), (DWORD[]){0}, ((void *)0));
^
.text
.def @feat.00;
.scl 3;
.type 0;
.endef
.globl @feat.00
.set @feat.00, 1
.def _mainCRTStartup;
.scl 2;
.type 32;
.endef
.globl _mainCRTStartup
.p2align 4, 0x90
_mainCRTStartup:
pushl %esi
subl $36, %esp
leal 5(%esp), %esi
pushl $31
pushl $L_mainCRTStartup.msg
pushl %esi
calll _memcpy
addl $12, %esp
pushl $-11
calll *__imp__GetStdHandle
addl $4, %esp
movl $0, (%esp)
movl %esp, %ecx
pushl $0
pushl %ecx
pushl $31
pushl %esi
pushl %eax
calll _WriteFile
addl $56, %esp
popl %esi
retl
.section .rdata,"dr"
L_mainCRTStartup.msg:
.asciz "012345678901234567890123456789"
1 warning generated.
Used to not happen on 6.0, where this was generated instead:
pushl %eax
pushl $-11
calll *__imp__GetStdHandle
Ltmp0:
addl $4, %esp
.loc 1 7 45 #
/tmp/compiler-explorer-compiler11862-54-b0lq0e.pt5wl/example.c:7:45
movl $0, (%esp)
movl %esp, %ecx
.loc 1 7 3 is_stmt 0 #
/tmp/compiler-explorer-compiler11862-54-b0lq0e.pt5wl/example.c:7:3
pushl $0
pushl %ecx
pushl $31
pushl $_mainCRTStartup.msg
pushl %eax
calll _WriteFile
Ltmp1:
addl $20, %esp
.loc 1 8 1 is_stmt 1 #
/tmp/compiler-explorer-compiler11862-54-b0lq0e.pt5wl/example.c:8:1
popl %eax
retl</pre>
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