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<base href="https://llvm.org/bugs/" />
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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 --- - ScalarEvolution::getConstantEvolutionLoopExitValue doesn't evualate loops corectly."
href="https://llvm.org/bugs/show_bug.cgi?id=27409">27409</a>
</td>
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<tr>
<th>Summary</th>
<td>ScalarEvolution::getConstantEvolutionLoopExitValue doesn't evualate loops corectly.
</td>
</tr>
<tr>
<th>Product</th>
<td>new-bugs
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Linux
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>new bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>williams@coherentlogix.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=16230" name="attach_16230" title="Test Case but write up and output files.">attachment 16230</a> <a href="attachment.cgi?id=16230&action=edit" title="Test Case but write up and output files.">[details]</a></span>
Test Case but write up and output files.
When we run the following test case.
#include <stdio.h>
int main() {
int Test[10] = { 10, 9, 8, 7, 6, 5, 4, 3, 2, 1 };
int i;
int Sum = 0;
for(i = 0 ; i < 1 ; i++) {
Sum += Test[i] ;
}
printf("Sum = %d\n", Sum);
Sum = 0;
for(i = 0 ; i < 2 ; i++) {
Sum += Test[i] ;
}
printf("Sum = %d\n", Sum);
Sum = 0;
for(i = 0 ; i < 3 ; i++) {
Sum += Test[i] ;
}
printf("Sum = %d\n", Sum);
Sum = 0;
for(i = 3 ; i < 7 ; i++) {
Sum += Test[i] ;
}
printf("Sum = %d\n", Sum);
Sum = 0;
for(i = 7 ; i < 10 ; i++) {
Sum += Test[i] ;
}
printf("Sum = %d\n", Sum);
Sum = 0;
for(i = 8 ; i < 10 ; i++) {
Sum += Test[i] ;
}
printf("Sum = %d\n", Sum);
Sum = 0;
for(i = 9 ; i < 10 ; i++) {
Sum += Test[i] ;
}
printf("Sum = %d\n", Sum);
Sum = 0;
for(i = 0 ; i < 10 ; i++) {
Sum += Test[i] ;
}
printf("Sum = %d\n", Sum);
return 0;
}
We expect the following output:
Sum = 10
Sum = 19
Sum = 27
Sum = 22
Sum = 6
Sum = 3
Sum = 1
Sum = 55
However when we ran this program with clang using -O3 we got the following
output:
Sum = 10
Sum = 10
Sum = 19
Sum = 18
Sum = 6
Sum = 3
Sum = 1
Sum = 55
We have tracked the problem down to the following function:
onstant *
ScalarEvolution::getConstantEvolutionLoopExitValue(PHINode *PN,
const APInt &BEs,
const Loop *L)</pre>
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