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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [Regression] Infinite loop in SoftenFloatOperand"
href="https://bugs.llvm.org/show_bug.cgi?id=34866">34866</a>
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<th>Summary</th>
<td>[Regression] Infinite loop in SoftenFloatOperand
</td>
</tr>
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<th>Product</th>
<td>libraries
</td>
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<th>Version</th>
<td>5.0
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Windows NT
</td>
</tr>
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<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>Common Code Generator Code
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>bmakam@codeaurora.org
</td>
</tr>
<tr>
<th>CC</th>
<td>chh@google.com, Florian.Hahn@arm.com, llvm-bugs@lists.llvm.org, mcrosier@codeaurora.org
</td>
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<th>Blocks</th>
<td>34492
</td>
</tr></table>
<p>
<div>
<pre>The following code no longer compiles:
$ cat test.c
typedef unsigned __int128 u128_t;
typedef __float128 f128_t;
typedef union
{
f128_t f;
u128_t i;
} union128_t;
int test(volatile f128_t *start_X_ptr, volatile f128_t *start_Y_ptr)
{
for (unsigned iter_count = 1; iter_count <= 2; iter_count++)
{
union128_t read_valX = { .f = *start_X_ptr };
union128_t read_valY = { .f = *start_Y_ptr };
u128_t expected_val = ((iter_count - 1) * read_valY.i);
if (read_valX.i != expected_val)
{
return -1;
}
union128_t write_valX = { .i = (iter_count * (read_valX.i + 1)) };
union128_t write_valY = { .i = (read_valX.i + 1) };
*start_X_ptr = write_valX.f;
*start_Y_ptr = write_valY.f;
}
return 0;
}
because of an infinite loop in SoftenFloatOperand.
$ clang -O3 -c test.c -mllvm -debug-only=legalize-types
....
Soften float operand 0: t33: v16i8 = bitcast t20
Soften float operand 0: t33: v16i8 = bitcast t20
Soften float operand 0: t33: v16i8 = bitcast t20
Soften float operand 0: t33: v16i8 = bitcast t20
Soften float operand 0: t33: v16i8 = bitcast t20
Soften float operand 0: t33: v16i8 = bitcast t20
Soften float operand 0: t33: v16i8 = bitcast t20
Soften float operand 0: t33: v16i8 = bitcast t20
Works with LLVM4.0.1: <a href="https://godbolt.org/g/W8cULV">https://godbolt.org/g/W8cULV</a>
I suspect this was introduced in r254653 and got exposed sometime between
03/14/2017 and 03/17/2017.</pre>
</div>
</p>
<div id="referenced">
<hr style="border: 1px dashed #969696">
<b>Referenced Bugs:</b>
<ul>
<li>
[<a class="bz_bug_link
bz_status_NEW "
title="NEW - [meta] 5.0.1 Release Blockers"
href="https://bugs.llvm.org/show_bug.cgi?id=34492">Bug 34492</a>] [meta] 5.0.1 Release Blockers
</li>
</ul>
</div>
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