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<base href="https://bugs.llvm.org/">
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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 - [LSR] Bad code generation from LSR"
href="https://bugs.llvm.org/show_bug.cgi?id=36854">36854</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>[LSR] Bad code generation from LSR
</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>Windows NT
</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>
<tr>
<th>Component</th>
<td>Loop Optimizer
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>junbuml@codeaurora.org
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>For the C code below, the transformation done by LSR cause bad code generation
on AArch64.
int isTrue();
void test(int M, int *P, int *P2, int *P3, int *P4) {
int t = 0;
for (int k = 1; k <= M; ++k) {
P[k] = P2[k-1] + P[k-1];
P3[k] = P2[k-1] + P3[k-1];
if (isTrue()) {
P4[k] = P[k] + P2[k];
}
}
}
# Current code generation -----------------------------------------
.LBB0_2:
ldr w8, [x19]
ldur w9, [x20, #-4]
add w8, w9, w8
str w8, [x20]
ldr w8, [x19]
ldur w9, [x21, #-4]
add w8, w9, w8
str w8, [x21]
bl isTrue
cbz w0, .LBB0_4
// %bb.3: // %if.then
ldr w8, [x20]
ldr w9, [x19, #4]
add w8, w9, w8
str w8, [x23]
.LBB0_4: // %for.inc
// in Loop: Header=BB0_2 Depth=1
subs x22, x22, #1 // =1
add x20, x20, #4 // =4
add x21, x21, #4 // =4
add x23, x23, #4 // =4
add x19, x19, #4 // =4
b.ne .LBB0_2
#Code when skipping LSR --------------------------------------------------
.LBB0_2: // %for.body
// =>This Inner Loop Header: Depth=1
lsl x25, x24, #2
sub x8, x25, #4 // =4
ldr w9, [x21, x8]
ldr w10, [x22, x8]
add w9, w10, w9
str w9, [x22, x25]
ldr w9, [x21, x8]
ldr w8, [x20, x8]
add w8, w8, w9
str w8, [x20, x25]
bl isTrue
cbz w0, .LBB0_4
// %bb.3: // %if.then
// in Loop: Header=BB0_2 Depth=1
ldr w8, [x22, x25]
ldr w9, [x21, x25]
add w8, w9, w8
str w8, [x19, x25]
.LBB0_4: // %for.inc
// in Loop: Header=BB0_2 Depth=1
add x24, x24, #1 // =1
cmp x24, x23
b.ne .LBB0_2</pre>
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