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Instrumentation of memory accesses to use ThreadSanitizer (TSan) for data race detection. This module contains an instrumentation pass on Cmm, where most of the instrumentation happens.
TSan requires to instrument all memory accesses (to mutable data), thread spawning and joining, mutex operations, and all such events that are relevant for parallelism. Thread and mutex operations are instrumented by the C compiler via the runtime. Instrumentation calls are FFI (C) calls.
TSan also requires to instrument the entry and exit of each function. TSan records function entries and exits along with other events in a history in to be able to print backtraces of an event (memory access, mutex creation...) when needed.
In addition to this static instrumentation, we must let TSan know when a function is exited due to an exception or when performing effect, or re-entered when resuming a continuation. This dynamic instrumentation is performed by dedicated runtime functions in runtime/tsan.c. These functions are called from the assembly chunks of the runtime.
Instrumentation of a Cmm.expression: instrument memory accesses, and surround the expression by external calls to __tsan_func_entry and __tsan_func_exit. If the expression tail is a function call, then __tsan_func_exit is inserted before that call.
Surround an expression by external calls to __tsan_func_entry and __tsan_func_exit. If the expression tail is a function call, then __tsan_func_exit is inserted before that call.
Call to __tsan_init, which should be called at least once in the compiled program, before other __tsan_* API functions. __tsan_init is idempotent, i.e. can be called more than once without consequences.