https://llvm.org/bugs/show_bug.cgi?id=28991
Bug ID: 28991
Summary: Incorrect sample profiles at O3
Product: new-bugs
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P
Component: new bugs
Assignee: unassignedb...@nondot.org
Reporter: dcalla...@fb.com
CC: llvm-bugs@lists.llvm.org
Classification: Unclassified
Created attachment 16963
--> https://llvm.org/bugs/attachment.cgi?id=16963&action=edit
Tar file of script and input files
bug2.sh generates the reproduction where we compile a training program either
-00 or -03.
The -O0 training yield this sample
Function: _Z8clampSumPdidd: 105434939, 1, 14 sampled lines
Samples collected in the function's body {
0: 1
1: 1
2.1: 949899
2.2: 949797
3: 949833
4: 0
5: 949926
6: 949896
7: 0
8: 949929
9: 949904
11: 949889
12: 949809
14: 4
}
while the -O3 training yields this sample
Function: _Z8clampSumPdidd: 76108151, 2, 9 sampled lines
Samples collected in the function's body {
0: 2
2.1: 1435907
3: 1436091
6: 1436048
7: 1436032
9: 2
11: 1435984
12: 1435974
14: 2
}
Note the differences in values for relative statements 7 and 9.
The corresponding branch_weights are
!74 = !{!"branch_weights", i32 1, i32 949905}
and
!74 = !{!"branch_weights", i32 1436033, i32 3}
The -O3 sample inverts the relative weights relative to the (correct) -O0
sample.
The attached tar file has bug2.sh, bug.cc and main.cc and a snapshot of bug2.sh
output.
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