3 Commits

Author	SHA1	Message	Date
Rich Kadel	ba18978875	LLVM IR coverage encoding aligns closer to Clang's ... I found some areas for improvement while attempting to debug the SegFault issue when running rust programs compiled using MSVC, with coverage instrumentation. I discovered that LLVM's coverage writer was generating incomplete function name variable names (that's not a typo: the name of the variable that holds a function name). The existing implementation used one-up numbers to distinguish variables, and correcting the names did not fix the MSVC coverage bug, but the fix in this PR makes the names and resulting LLVM IR easier to follow and more consistent with Clang's implementation. I also changed the way the `-Zinstrument-coverage` option is supported in symbol_export.rs. The original implementation was incorrect, and the corrected version matches the handling for `-Zprofile-generate`, as it turns out. (An argument could be made that maybe `-Zinstrument-coverage` should automatically enable `-Cprofile-generate`. In fact, if `-Cprofile-generate` is analagous to Clang's `-fprofile-generate`, as some documentation implies, Clang always requires this flag for its implementation of source-based code coverage. This would require a little more validation, and if implemented, would probably require updating some of the user-facing messages related to `-Cprofile-generate` to not be so specific to the PGO use case.) None of these changes fixed the MSVC coverage problems, but they should still be welcome improvements. Lastly, I added some additional FIXME comments in instrument_coverage.rs describing issues I found with the generated LLVM IR that would be resolved if the coverage instrumentation is injected with a `Statement` instead of as a new `BasicBlock`. I describe seven advantages of this change, but it requires some discussion before making a change like this.	2020-08-14 02:24:35 -07:00
Rich Kadel	12ddd6073a	Fixed coverage map issues; better aligned with LLVM APIs ... Found some problems with the coverage map encoding when testing with more than one counter per function. While debugging, I realized some better ways to structure the Rust implementation of the coverage mapping generator. I refactored somewhat, resulting in less code overall, expanded coverage of LLVM Coverage Map capabilities, and much closer alignment with LLVM data structures, APIs, and naming. This should be easier to follow and easier to maintain.	2020-07-25 07:39:51 -07:00
Rich Kadel	a6f8b8a211	Generating the coverage map ... rustc now generates the coverage map and can support (limited) coverage report generation, at the function level. Example: $ BUILD=$HOME/rust/build/x86_64-unknown-linux-gnu $ $BUILD/stage1/bin/rustc -Zinstrument-coverage \ $HOME/rust/src/test/run-make-fulldeps/instrument-coverage/main.rs $ LLVM_PROFILE_FILE="main.profraw" ./main called $ $BUILD/llvm/bin/llvm-profdata merge -sparse main.profraw -o main.profdata $ $BUILD/llvm/bin/llvm-cov show --instr-profile=main.profdata main 1| 1|pub fn will_be_called() { 2| 1| println!("called"); 3| 1|} 4| | 5| 0|pub fn will_not_be_called() { 6| 0| println!("should not have been called"); 7| 0|} 8| | 9| 1|fn main() { 10| 1| let less = 1; 11| 1| let more = 100; 12| 1| 13| 1| if less < more { 14| 1| will_be_called(); 15| 1| } else { 16| 1| will_not_be_called(); 17| 1| } 18| 1|}	2020-07-17 11:49:35 -07:00