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<base href="https://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - 4.0 Regression in llvm.powi.f64 lowering on ARM"
href="https://llvm.org/bugs/show_bug.cgi?id=30543">30543</a>
</td>
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<tr>
<th>Summary</th>
<td>4.0 Regression in llvm.powi.f64 lowering on ARM
</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>
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<th>OS</th>
<td>Linux
</td>
</tr>
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<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>Backend: ARM
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>yyc1992@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Compiling the following IR on arm
```
target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"
target triple = "armv7l-unknown-linux-gnueabihf"
@.str = private unnamed_addr constant [4 x i8] c"%f\0A\00", align 1
; Function Attrs: noinline norecurse nounwind readnone
define double @f(double, i32) #0 {
top:
%2 = tail call double @llvm.powi.f64(double %0, i32 %1)
ret double %2
}
; Function Attrs: nounwind readnone
declare double @llvm.powi.f64(double, i32)
; Function Attrs: nounwind
define i32 @main() {
%1 = tail call double @f(double 2.000000e+00, i32 62)
%2 = tail call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([4 x i8],
[4 x i8]* @.str, i32 0, i32 0), double %1)
ret i32 0
}
; Function Attrs: nounwind
declare i32 @printf(i8* nocapture readonly, ...)
attributes #0 = { noinline }
```
prints 2.0 instead of what 2^62 should be.
This is a regression in llvm 4.0 and is causing a lot of test failures in
julia.
Difference in the assembly
```
- .save {r11, lr}
- push {r11, lr}
- mov r2, r0
- vmov r0, r1, d0
- bl __powidf2
- vmov d0, r0, r1
- pop {r11, pc}
+ b __powidf2
```
GDB confirmed that the input value to `__powidf2` is wrong.
Currently bisecting.</pre>
</div>
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