Add profiling support, through the rustc -Z profile flag.

When -Z profile is passed, the GCDAProfiling LLVM pass is added
to the pipeline, which uses debug information to instrument the IR.
After compiling with -Z profile, the $(OUT_DIR)/$(CRATE_NAME).gcno
file is created, containing initial profiling information.
After running the program built, the $(OUT_DIR)/$(CRATE_NAME).gcda
file is created, containing branch counters.

The created *.gcno and *.gcda files can be processed using
the "llvm-cov gcov" and "lcov" tools. The profiling data LLVM
generates does not faithfully follow the GCC's format for *.gcno
and *.gcda files, and so it will probably not work with other tools
(such as gcov itself) that consume these files.

1 files changed, 1 insertions, 0 deletions

diff --git a/configure b/configure
index c5ecc223689..ced7377a236 100755
--- a/configure
+++ b/configure
@@ -452,6 +452,7 @@ opt vendor 0 "enable usage of vendored Rust crates"
 opt sanitizers 0 "build the sanitizer runtimes (asan, lsan, msan, tsan)"
 opt dist-src 1 "when building tarballs enables building a source tarball"
 opt cargo-openssl-static 0 "static openssl in cargo"
+opt profiler 0 "build the profiler runtime"
 
 # Optimization and debugging options. These may be overridden by the release channel, etc.
 opt_nosave optimize 1 "build optimized rust code"