Debug Info in LLVM keeps improving!
Everyone wants an ideal debugging user experience, that includes seeing no optimized_out variables during the debugging of an optimized binary. It is not an easy task for compiler developers to achieve 100% coverage for all the variables, but LLVM community is doing a great job! I’ve been following the improvements with the respect to the location coverage over the LLVM releases [0] (not only following, I also worked on improving the Debug Info :) ) and the recent numbers look amazing. In the link I mentioned [0], we can see that LLVM 6.0 generated the binary with only 45% of PC coverage, but now LLVM 16.0.4 generates binary with 71% of PC coverage. Nice!
First of all, let me mention that I used the binutils-gdb as testbed, compiled with -g -O2. By using the [1], the results look as:
LLVM 15.0.7
$ llvm-locstats gdb-built-with-clang-15-0-7
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Debug Location Statistics
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cov% samples percentage(~)
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0% 9352 1%
(0%,10%) 10743 1%
[10%,20%) 17696 3%
[20%,30%) 11934 2%
[30%,40%) 9973 1%
[40%,50%) 8946 1%
[50%,60%) 10828 1%
[60%,70%) 10696 1%
[70%,80%) 13399 2%
[80%,90%) 15424 2%
[90%,100%) 14290 2%
100% 412840 75%
=================================================
-the number of debug variables processed: 546121
-PC ranges covered: 70%
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-total availability: 62%
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LLVM 16.0.4
$ llvm-locstats gdb-built-with-clang-16-0-4
=================================================
Debug Location Statistics
=================================================
cov% samples percentage(~)
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0% 8816 1%
(0%,10%) 10153 1%
[10%,20%) 13014 2%
[20%,30%) 15861 2%
[30%,40%) 10036 1%
[40%,50%) 9203 1%
[50%,60%) 10651 1%
[60%,70%) 11061 2%
[70%,80%) 13719 2%
[80%,90%) 14158 2%
[90%,100%) 13783 2%
100% 416758 76%
=================================================
-the number of debug variables processed: 547213
-PC ranges covered: 71%
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-total availability: 65%
=================================================
Compare llvm 16.0.4 vs llvm 15.0.7
[1] llvm-locstats