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<base href="https://llvm.org/bugs/" />
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<body><table border="1" cellspacing="0" cellpadding="8">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - [ppc] Convert char/short to double through memory"
href="https://llvm.org/bugs/show_bug.cgi?id=31144">31144</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>[ppc] Convert char/short to double through memory
</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>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>Backend: PowerPC
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>carrot@google.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Compile following code with options -m64 -O2
extern void bar(double);
void foo(char* p)
{
bar(*p);
}
void foo1(unsigned short* p)
{
bar(*p);
}
LLVM generates:
.Lfunc_lep0:
.localentry foo, .Lfunc_lep0-.Lfunc_gep0
# BB#0: # %entry
mflr 0
std 31, -8(1)
std 0, 16(1)
stdu 1, -112(1)
lbz 3, 0(3) // load original value
mr 31, 1
addi 4, 31, 100
stw 3, 100(31) // store
ori 2, 2, 0
lxsiwzx 0, 0, 4 // load
xscvuxddp 1, 0
bl bar
nop
addi 1, 1, 112
ld 0, 16(1)
ld 31, -8(1)
mtlr 0
blr
Note that lxsiwzx is immediately following stw, they access the same memory, it
is very slow. Instruction mtvsrwz can be used to move a value from integer
register to VSX register directly.</pre>
</div>
</p>
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