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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Miscompile with x86 hosted release compiler targeting x64"
href="http://llvm.org/bugs/show_bug.cgi?id=19644">19644</a>
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<th>Summary</th>
<td>Miscompile with x86 hosted release compiler targeting x64
</td>
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<th>Product</th>
<td>libraries
</td>
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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>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>MC
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>douglas_yung@playstation.sony.com
</td>
</tr>
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<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
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<th>Classification</th>
<td>Unclassified
</td>
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<div>
<pre>I am running an x86 linux hosted release compiler targeting x64 linux, and I am
seeing the dumper which writes the generated machine instructions to a file
seems to be messing up somewhere in the process. Note that this only seems to
occur in the x86 release compiler when targeting x64. A debug+asserts build of
the same compiler does NOT exhibit this issue.
Test environment:
• Compiler: i386-pc-linux-gnu
• Compiler build: Release (does not repro with Debug+Asserts built compiler)
• Target: x86_64-pc-linux-gnu
• Host OS: Linux (Ubuntu 13.10)
• SVN Revision: 207280
• Compiler used to build LLVM: gcc (Ubuntu/Linaro 4.8.1-10ubuntu9) 4.8.1
The LLVM IR which reproduces the issue is the following:
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-pc-linux-gnu"
%struct.S5303X7 = type { i56, [2 x i32] }
; Function Attrs: uwtable
define internal void @_ZL12Test_S5303X7v() #0 {
%lv = alloca %struct.S5303X7*, align 8
%1 = call noalias i8* @_Znwm(i64 16) #3
%2 = bitcast i8* %1 to %struct.S5303X7*
store %struct.S5303X7* %2, %struct.S5303X7** %lv, align 8
%3 = load %struct.S5303X7** %lv, align 8
%4 = bitcast %struct.S5303X7* %3 to i64*
%5 = load i64* %4, align 4
%6 = and i64 %5, -2251799813685249
store i64 %6, i64* %4, align 4
ret void
}
; Function Attrs: nobuiltin
declare noalias i8* @_Znwm(i64) #2
To see the issue, compile this using a x86 hosted Release build of the compiler
and use the command “llc repro.ll –filetype=asm –o repro.s –O0”. If you look at
the generated assembly file, you will see that the constant “-2251799813685249”
has been changed to “-1”. If you compile with a Debug+Asserts compiler, the
constant is unaltered. If you add the options “-print-machineinstrs” and
“-show-mc-inst” you can see that after each pass the constant is still correct,
but once it gets written to the file, it is incorrectly changed to -1.</pre>
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