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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 - More efficient remainder lowering"
href="https://bugs.llvm.org/show_bug.cgi?id=32464">32464</a>
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<tr>
<th>Summary</th>
<td>More efficient remainder lowering
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</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>
<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>Backend: AArch64
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>davide@freebsd.org
</td>
</tr>
<tr>
<th>CC</th>
<td>efriedma@codeaurora.org, llvm-bugs@lists.llvm.org, mcrosier@codeaurora.org, t.p.northover@gmail.com
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<pre>Given the following IR:
<span class="quote">> cat remainder.ll</span >
target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
target triple = "aarch64--linux-gnu"
define i32 @tinky(i32 %j) local_unnamed_addr #0 {
entry:
%rem = srem i32 %j, 255
ret i32 %rem
}
attributes #0 = { norecurse nounwind readnone
"correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false"
"less-precise-fpmad"="false" "no-frame-pointer-elim"="true"
"no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false"
"no-jump-tables"="false" "no-nans-fp-math"="false"
"no-signed-zeros-fp-math"="false" "no-trapping-math"="false"
"stack-protector-buffer-size"="8" "target-cpu"="cortex-a53"
"target-features"="+crc,-crypto,-fp-armv8,-neon" "unsafe-fp-math"="false"
"use-soft-float"="false" }
!llvm.ident = !{!0}
Fast-isel seems to generate slightly faster/shorter code than SelectionDAG:
<span class="quote">> C:\Users\fluttershy\work\llvm-msvc\Debug\bin\llc.exe -O3 -mcpu=cortex-a53 remainder.ll -o - -fast-isel</span >
.text
.file "remainder.ll"
.globl tinky
.p2align 2
.type tinky,@function
tinky: // @tinky
// BB#0: // %entry
orr w8, wzr, #0xff
sdiv w9, w0, w8
msub w0, w9, w8, w0
ret
.Lfunc_end0:
.size tinky, .Lfunc_end0-tinky
.ident "clang version 5.0.0 (trunk 298784) (llvm/trunk 298825)"
.section ".note.GNU-stack","",@progbits
<span class="quote">> C:\Users\fluttershy\work\llvm-msvc\Debug\bin\llc.exe -O3 -mcpu=cortex-a53 remainder.ll -o -</span >
.text
.file "remainder.ll"
.globl tinky
.p2align 2
.type tinky,@function
tinky: // @tinky
// BB#0: // %entry
orr w8, wzr, #0xff
sdiv w8, w0, w8
lsl w9, w8, #8
sub w8, w9, w8
sub w0, w0, w8
ret
.Lfunc_end0:
.size tinky, .Lfunc_end0-tinky
.ident "clang version 5.0.0 (trunk 298784) (llvm/trunk 298825)"
.section ".note.GNU-stack","",@progbits</pre>
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