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<base href="http://llvm.org/bugs/" />
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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 --- - use imul instead of lea to implement multiplication when the argument is call-by-reference"
href="http://llvm.org/bugs/show_bug.cgi?id=19047">19047</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>use imul instead of lea to implement multiplication when the argument is call-by-reference
</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>MacOS X
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>Backend: X86
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>cfy1990@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>$ clang++ --version
Apple LLVM version 5.0 (clang-500.2.79) (based on LLVM 3.3svn)
Target: x86_64-apple-darwin13.1.0
Thread model: posix
$ cat test.cc
void foo(int &a,int &b){
b = a * 5;//imull $5, (%rdi), %eax
}
int foo(int a){
return a *5; //leal (%rdi,%rdi,4), %eax
}
$ clang++ -Ofast test.cc -c -S -o -
.section __TEXT,__text,regular,pure_instructions
.globl __Z3fooRiS_
.align 4, 0x90
__Z3fooRiS_: ## @_Z3fooRiS_
.cfi_startproc
## BB#0:
pushq %rbp
Ltmp2:
.cfi_def_cfa_offset 16
Ltmp3:
.cfi_offset %rbp, -16
movq %rsp, %rbp
Ltmp4:
.cfi_def_cfa_register %rbp
imull $5, (%rdi), %eax
movl %eax, (%rsi)
popq %rbp
ret
.cfi_endproc
.globl __Z3fooi
.align 4, 0x90
__Z3fooi: ## @_Z3fooi
.cfi_startproc
## BB#0:
pushq %rbp
Ltmp7:
.cfi_def_cfa_offset 16
Ltmp8:
.cfi_offset %rbp, -16
movq %rsp, %rbp
Ltmp9:
.cfi_def_cfa_register %rbp
leal (%rdi,%rdi,4), %eax
popq %rbp
ret
.cfi_endproc
.subsections_via_symbols</pre>
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