https://bugs.llvm.org/show_bug.cgi?id=37456
Bug ID: 37456
Summary: -time-compilations=N for N > 1 drops data points
randomly
Product: tools
Version: trunk
Hardware: PC
OS: MacOS X
Status: NEW
Severity: normal
Priority: P
Component: llc
Assignee: unassignedb...@nondot.org
Reporter: rteres...@apple.com
CC: llvm-bugs@lists.llvm.org
-time-compilations=N for N > 1 drops data points randomly
# X86 DAG->DAG Instruction Selection, runs for about 1 ms
> for _ in (seq 20); ./bin/llc -mtriple x86_64-- -O0
> ../../test/CodeGen/X86/fast-isel-x86-64.ll -o /dev/null -time-passes
> -time-compilations=1000 2>&1 | grep -c 'X86 DAG->DAG Instruction Selection';
> end
862
885
842
864
865
846
861
874
858
840
865
847
874
853
875
873
859
869
860
876
>
# Fast Register Allocator, runs for about 0.2 ms
> for _ in (seq 20); ./bin/llc -mtriple x86_64-- -O0
> ../../test/CodeGen/X86/fast-isel-x86-64.ll -o /dev/null -time-passes
> -time-compilations=1000 2>&1 | grep -c 'Fast Register Allocator'; end
258
255
233
251
264
254
280
245
262
260
276
262
254
271
272
263
260
260
257
279
>
# Rewrite Symbols, runs for unmeasurably small amount of time
> for _ in (seq 20); ./bin/llc -mtriple x86_64-- -O0
> ../../test/CodeGen/X86/fast-isel-x86-64.ll -o /dev/null -time-passes
> -time-compilations=1000 2>&1 | grep -c 'Rewrite Symbols'; end
900
893
884
906
887
906
885
899
897
883
909
870
911
900
898
912
892
894
896
908
>
It behaves this way for any input LLVM IR I've tried, big (like sqlite3
amalgamation) and small (like shown above), for any target I've tried (x86-64
and AArch64), and any pass.
Tried on trunk llc as of time of writing (r332192) under macOS on x86-64 iMac.
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