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<body><span class="vcard"><a class="email" href="mailto:markmi@dsl-only.net" title="Mark Millard <markmi@dsl-only.net>"> <span class="fn">Mark Millard</span></a>
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<a class="bz_bug_link
bz_status_REOPENED "
title="REOPENED - Clang 4.0.0's "Target: powerpc-unknown-freebsd11.0" code generation is violating the SVR4 ABI (SEGV can result)"
href="https://bugs.llvm.org/show_bug.cgi?id=26519">bug 26519</a>
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<table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>What</th>
<th>Removed</th>
<th>Added</th>
</tr>
<tr>
<td style="text-align:right;">Status</td>
<td>RESOLVED
</td>
<td>REOPENED
</td>
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<td style="text-align:right;">Resolution</td>
<td>FIXED
</td>
<td>---
</td>
</tr></table>
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<b><a class="bz_bug_link
bz_status_REOPENED "
title="REOPENED - Clang 4.0.0's "Target: powerpc-unknown-freebsd11.0" code generation is violating the SVR4 ABI (SEGV can result)"
href="https://bugs.llvm.org/show_bug.cgi?id=26519#c24">Comment # 24</a>
on <a class="bz_bug_link
bz_status_REOPENED "
title="REOPENED - Clang 4.0.0's "Target: powerpc-unknown-freebsd11.0" code generation is violating the SVR4 ABI (SEGV can result)"
href="https://bugs.llvm.org/show_bug.cgi?id=26519">bug 26519</a>
from <span class="vcard"><a class="email" href="mailto:markmi@dsl-only.net" title="Mark Millard <markmi@dsl-only.net>"> <span class="fn">Mark Millard</span></a>
</span></b>
<pre>(In reply to Krzysztof Parzyszek from <a href="show_bug.cgi?id=26519#c19">comment #19</a>)
<span class="quote">> Committed a fix in r302183.</span >
Bad news: Another code generation error, this
time demonstrated in compiling part of perl5. . .
(I tried to build a port that indirectly
tried build perl5 but perl5's miniperl crashes.)
/usr/obj/portswork/usr/ports/lang/perl5.24/work/perl-5.24.1/numeric.c
has Perl_cast_iv(NV f) for which clang double stores
two different things to one address [24(r1)]. Below
the => lines are the double store, the second
destroying the r30 value that was saved in the first:
Dump of assembler code for function Perl_cast_iv:
0x0196a114 <+0>: mflr r0
0x0196a118 <+4>: stw r0,4(r1)
0x0196a11c <+8>: stwu r1,-32(r1)
0x0196a120 <+12>: stw r31,28(r1)
=> 0x0196a124 <+16>: stw r30,24(r1)
0x0196a128 <+20>: mr r31,r1
0x0196a12c <+24>: mfcr r12
=> 0x0196a130 <+28>: stw r12,24(r31)
Note: r31 == r1 for that second "=>" line.
The return code sequence has a similar
problem: two loads from the same address.
Note: r31 == r1 here too.
=> 0x0196a1bc <+168>: lwz r12,24(r31)
0x0196a1c0 <+172>: lwz r0,36(r1)
0x0196a1c4 <+176>: lwz r31,28(r1)
=> 0x0196a1c8 <+180>: lwz r30,24(r1)
0x0196a1cc <+184>: mtcrf 32,r12
0x0196a1d0 <+188>: addi r1,r1,32
0x0196a1d4 <+192>: mtlr r0
0x0196a1d8 <+196>: blr
The Perl_cast_iv source code looks like:
IV
Perl_cast_iv(NV f)
{
if (f < IV_MAX_P1)
return f < IV_MIN ? IV_MIN : (IV) f;
if (f < UV_MAX_P1) {
#if CASTFLAGS & 2
/* For future flexibility allowing for sizeof(UV) >= sizeof(IV) */
if (f < UV_MAX_P1_HALF)
return (IV)(UV) f;
f -= UV_MAX_P1_HALF;
return (IV)(((UV) f) | (1 + (UV_MAX >> 1)));
#else
return (IV)(UV) f;
#endif
}
return f > 0 ? (IV)UV_MAX : 0 /* NaN */;
}</pre>
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