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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [arm] After 186155b89c2d, fatal error: error in backend: Cannot select: t28: i32 = ARMISD::QADD8b t33, t35"
href="https://bugs.llvm.org/show_bug.cgi?id=45677">45677</a>
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<th>Summary</th>
<td>[arm] After 186155b89c2d, fatal error: error in backend: Cannot select: t28: i32 = ARMISD::QADD8b t33, t35
</td>
</tr>
<tr>
<th>Product</th>
<td>new-bugs
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>All
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>enhancement
</td>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>new bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>dimitry@andric.com
</td>
</tr>
<tr>
<th>CC</th>
<td>htmldeveloper@gmail.com, llvm-bugs@lists.llvm.org
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<pre>Recently I got the following fatal backend error when building
<a href="https://github.com/freebsd/freebsd/blob/master/sys/dev/sound/pcm/feeder_mixer.c">https://github.com/freebsd/freebsd/blob/master/sys/dev/sound/pcm/feeder_mixer.c</a>
for armv5 (on FreeBSD this apparently defaults to -target-cpu arm1022e):
fatal error: error in backend: Cannot select: t37: i32 = ARMISD::QADD8b t43,
t44
t43: i32,ch = load<(load 1 from %ir.8, !tbaa !65), sext from i8> t0, t5,
undef:i32
t5: i32 = add t2, t4
t2: i32,ch = CopyFromReg t0, Register:i32 %1
t1: i32 = Register %1
t4: i32,ch = CopyFromReg t0, Register:i32 %2
t3: i32 = Register %2
t14: i32 = undef
t44: i32,ch = load<(load 1 from %ir.11, !tbaa !65), sext from i8> t0, t8,
undef:i32
t8: i32 = add t7, t4
t7: i32,ch = CopyFromReg t0, Register:i32 %0
t6: i32 = Register %0
t4: i32,ch = CopyFromReg t0, Register:i32 %2
t3: i32 = Register %2
t14: i32 = undef
In function: feed_mixer_S8NE
The full test case reduces to:
// clang -cc1 -triple armv5e--- -S -target-cpu arm1022e -O1 feeder_mixer-min.c
char *a;
char b;
int c;
void d() {
int e, f = *(signed char *)a;
c = *(signed char *)1;
e = f + c;
f = e > 127 ? 127 : e < -0x80 ? 128 : e;
b = f;
}
Interestingly, this regressed with the *very* last Subversion commit to trunk,
<a href="https://reviews.llvm.org/rL375505">https://reviews.llvm.org/rL375505</a> ("[InstCombine] Signed saturation patterns"),
a.k.a. <a href="https://reviews.llvm.org/rG186155b89c2d">https://reviews.llvm.org/rG186155b89c2d</a>, and
<a href="https://reviews.llvm.org/D68651">https://reviews.llvm.org/D68651</a>.
It still reproduces with recent llvm master.</pre>
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