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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - fast selector fails to select many blocks"
href="http://llvm.org/bugs/show_bug.cgi?id=16991">16991</a>
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<th>Summary</th>
<td>fast selector fails to select many blocks
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</td>
</tr>
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<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>Linux
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Backend: PowerPC
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>echristo@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>From the trivial C code:
void EmptyLoop() {
for (long i = 0; i < 1000000000; ++i) {
}
}
We're missing in a few places:
ghostwheel:~> ~/builds/build-llvm/Debug+Asserts/bin/llc -fast-isel-verbose
empty_loop.ll -O0
FastISel miss: store i64 0, i64* %i, align 8
FastISel miss: br i1 %cmp, label %for.body, label %for.end
FastISel missed terminator: ret void
FastISel miss: store i64 %inc, i64* %i, align 8
and the full module:
; ModuleID = 'empty_loop.cpp'
target datalayout =
"E-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-f128:128:128-v128:128:128-n32:64"
target triple = "powerpc64--linux-gnu"
; Function Attrs: nounwind
define void @_Z9EmptyLoopv() #0 {
entry:
%i = alloca i64, align 8
store i64 0, i64* %i, align 8
br label %for.cond
for.cond: ; preds = %for.inc, %entry
%0 = load i64* %i, align 8
%cmp = icmp slt i64 %0, 1000000000
br i1 %cmp, label %for.body, label %for.end
for.body: ; preds = %for.cond
br label %for.inc
for.inc: ; preds = %for.body
%1 = load i64* %i, align 8
%inc = add nsw i64 %1, 1
store i64 %inc, i64* %i, align 8
br label %for.cond
for.end: ; preds = %for.cond
ret void
}
attributes #0 = { nounwind "less-precise-fpmad"="false"
"no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf"
"no-infs-fp-math"="false" "no-nans-fp-math"="false"
"stack-protector-buffer-size"="8" "unsafe-fp-math"="false"
"use-soft-float"="false" }</pre>
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