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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - msan: hoist value checks as much as possible"
href="https://bugs.llvm.org/show_bug.cgi?id=37670">37670</a>
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<th>Summary</th>
<td>msan: hoist value checks as much as possible
</td>
</tr>
<tr>
<th>Product</th>
<td>compiler-rt
</td>
</tr>
<tr>
<th>Version</th>
<td>unspecified
</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>
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<th>Component</th>
<td>compiler-rt
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>dvyukov@google.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>Currently msan places checks as late as possible, e.g. at branch on a bool
value. In some cases this makes it very hard to understand where the actual
uninit-ness come from.
Consider:
void foo(struct p *p)
{
if (p->x == p->y && // msan points here
p->w == p->z) // however it would be more useful to point
here
printf("x\n");
}
or:
int main()
{
volatile int l;
x = l;
p = malloc(1);
void *r = get();
if (r) // with -O2 msan points here
printf("x\n");
return 0;
}
volatile int x;
void* p;
void *get()
{
int y = x / 16; // but ideally it would point here, so that it's
clear that it's x the bad guy
if (!y)
return 0;
return p;
}</pre>
</div>
</p>
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