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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 - Wrong answer after loop vectorization"
href="https://bugs.llvm.org/show_bug.cgi?id=48583">48583</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Wrong answer after loop vectorization
</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>
<tr>
<th>OS</th>
<td>Windows NT
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>Backend: AArch64
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>guopeilin1@huawei.com
</td>
</tr>
<tr>
<th>CC</th>
<td>arnaud.degrandmaison@arm.com, llvm-bugs@lists.llvm.org, smithp352@googlemail.com, Ties.Stuij@arm.com
</td>
</tr></table>
<p>
<div>
<pre>This test case get the wrong answer after loop vectorization
====== commands =======
opt -loop-vectorize before-loop-vec.ll -o after-loop-vec.ll -S
llc after-loop-vec.ll -filetype=obj -o tmp.o
clang tmp.o -o tmp.out
========================
actually the test case's main job is doing a "361804 >> 18"
However the result shows that we finally get result 0 rather than 1, which is
a totally wrong answer
===== result =========
tmp.out: test-case.cpp:16: int main(): Assertion `a!=0 && "a should be 1"'
failed.
Aborted (core dumped)
===== before-loop-vec.ll ==========
target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
target triple = "aarch64-unknown-linux-gnu"
@a = dso_local local_unnamed_addr global i8 0, align 4
@b = dso_local local_unnamed_addr global [384 x i64] zeroinitializer, align 8
@c = dso_local local_unnamed_addr global i32 0, align 4
@.str.1 = private unnamed_addr constant [24 x i8] c"a!=0 && \22a should be
1\22\00", align 1
@.str.2 = private unnamed_addr constant [14 x i8] c"test-case.cpp\00", align 1
@__PRETTY_FUNCTION__.main = private unnamed_addr constant [11 x i8] c"int
main()\00", align 1
; Function Attrs: nofree norecurse nounwind
define dso_local void @_Z1dii(i32 %e, i32 %f) local_unnamed_addr {
entry:
br label %for.cond
for.cond: ; preds = %for.cond.cleanup5,
%entry
%g.0 = phi i32 [ 0, %entry ], [ %add11, %for.cond.cleanup5 ]
%cmp = icmp ult i32 %g.0, 11
br i1 %cmp, label %for.cond1.preheader, label %for.cond.cleanup
for.cond1.preheader: ; preds = %for.cond
%conv3 = and i32 %e, 255
%cmp417 = icmp ugt i32 %conv3, 0
br i1 %cmp417, label %for.body6.lr.ph, label %for.cond.cleanup5
for.body6.lr.ph: ; preds =
%for.cond1.preheader
br label %for.body6
for.cond.cleanup: ; preds = %for.cond
ret void
for.cond1.for.cond.cleanup5_crit_edge: ; preds = %for.inc
br label %for.cond.cleanup5
for.cond.cleanup5: ; preds =
%for.cond1.for.cond.cleanup5_crit_edge, %for.cond1.preheader
%add11 = add nuw nsw i32 %g.0, 2
br label %for.cond
for.body6: ; preds = %for.body6.lr.ph,
%for.inc
%h.018 = phi i8 [ 0, %for.body6.lr.ph ], [ %add, %for.inc ]
%0 = load i32, i32* @c, align 4
%tobool = icmp eq i32 %0, -1
br i1 %tobool, label %for.inc, label %if.then
if.then: ; preds = %for.body6
%1 = lshr i32 %f, 18
%conv7 = trunc i32 %1 to i8
store i8 %conv7, i8* @a, align 4
%idxprom = zext i8 %h.018 to i64
%arrayidx = getelementptr inbounds [384 x i64], [384 x i64]* @b, i64 0, i64
%idxprom
store i64 0, i64* %arrayidx, align 8
br label %for.inc
for.inc: ; preds = %for.body6,
%if.then
%add = add i8 %h.018, 3
%conv = zext i8 %add to i32
%cmp4 = icmp ugt i32 %conv3, %conv
br i1 %cmp4, label %for.body6, label %for.cond1.for.cond.cleanup5_crit_edge,
!llvm.loop !9
}
; Function Attrs: norecurse nounwind
define dso_local i32 @main() local_unnamed_addr {
entry:
call void @_Z1dii(i32 78, i32 361804)
%0 = load i8, i8* @a, align 4
%cmp = icmp eq i8 %0, 0
br i1 %cmp, label %cond.false, label %cond.end
cond.false: ; preds = %entry
call void @__assert_fail(i8* getelementptr inbounds ([24 x i8], [24 x i8]*
@.str.1, i64 0, i64 0), i8* getelementptr inbounds ([14 x i8], [14 x i8]*
@.str.2, i64 0, i64 0), i32 16, i8* getelementptr inbounds ([11 x i8], [11 x
i8]* @__PRETTY_FUNCTION__.main, i64 0, i64 0))
unreachable
cond.end: ; preds = %entry
ret i32 0
}
; Function Attrs: noreturn nounwind
declare dso_local void @__assert_fail(i8*, i8*, i32, i8*) local_unnamed_addr
!9 = distinct !{!9, !10, !11}
!10 = !{!"llvm.loop.vectorize.predicate.enable", i1 true}
!11 = !{!"llvm.loop.vectorize.enable", i1 true}</pre>
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