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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 - [Indvars] Incorrect hoisting of udiv/urem"
href="https://bugs.llvm.org/show_bug.cgi?id=35406">35406</a>
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<th>Summary</th>
<td>[Indvars] Incorrect hoisting of udiv/urem
</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>Windows NT
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>Scalar Optimizations
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>serguei.katkov@azul.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>Indvars does an incorrect transformation for the following reproducer:
=====================================================
; ModuleID = 'repro.ll'
;target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128-ni:1"
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128:1"
target triple = "x86_64-unknown-linux-gnu"
define i32 @test(i8* %p, i64* %p1) {
entry:
br label %loop1
loop1:
%local_0_ = phi i32 [ 8, %entry ], [ %9, %loop2.exit ]
%local_2_ = phi i32 [ 63864, %entry ], [ %local_2_43, %loop2.exit ]
%local_3_ = phi i32 [ 51, %entry ], [ %local_3_44, %loop2.exit ]
%0 = udiv i32 14, %local_0_
%1 = icmp ugt i32 %local_0_, 14
br i1 %1, label %exit, label %general_case24
general_case24:
; %2 = urem i32 60392, %0
%2 = udiv i32 60392, %0
br i1 false, label %loop2, label %loop2.exit
loop2:
%local_1_56 = phi i32 [ %2, %general_case24 ], [ %3, %loop2 ]
%local_2_57 = phi i32 [ 1, %general_case24 ], [ %7, %loop2 ]
%3 = add i32 %local_1_56, -1
%4 = load i64* %p1, align 8
; %4 = load atomic i64, i64* %p1 unordered, align 8
%5 = sext i32 %3 to i64
%6 = sub i64 %4, %5
; store atomic i64 %6, i64* %p1 unordered, align 8
store i64 %6, i64* %p1, align 8
%7 = add nuw nsw i32 %local_2_57, 1
%8 = icmp ugt i32 %local_2_57, 7
br i1 %8, label %loop2.exit, label %loop2
loop2.exit:
%local_2_43 = phi i32 [ %local_2_, %general_case24 ], [ 9, %loop2 ]
%local_3_44 = phi i32 [ %local_3_, %general_case24 ], [ %local_1_56, %loop2 ]
%9 = add nuw nsw i32 %local_0_, 1
%10 = icmp ugt i32 %local_0_, 129
br i1 %10, label %exit, label %loop1
exit:
ret i32 0
}
================================================
opt --indvars -S repro.ll
results in
================================================
...
loop1: ; preds = %loop2.exit, %entry
%indvars.iv = phi i32 [ %indvars.iv.next, %loop2.exit ], [ 8, %entry ]
%0 = udiv i32 14, %indvars.iv
%1 = udiv i32 60392, %0
%2 = zext i32 %1 to i64
%3 = udiv i32 14, %indvars.iv
%4 = icmp ugt i32 %indvars.iv, 14
br i1 %4, label %exit, label %general_case24
...
================================================
%1 = udiv i32 60392, %0
instruction causes a division by zero in case %indvars.iv == 15.</pre>
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