[compiler-rt] [llvm] [msan] Add experimental '-mllvm -msan-embed-faulting-instruction' and MSAN_OPTIONS=print_faulting_instruction (PR #136539)

[Thurston Dang via llvm-commits]

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@@ -25,6 +25,11 @@ MSAN_FLAG(bool, poison_stack_with_zeroes, false, "")
 MSAN_FLAG(bool, poison_in_malloc, true, "")
 MSAN_FLAG(bool, poison_in_free, true, "")
 MSAN_FLAG(bool, poison_in_dtor, true, "")
+MSAN_FLAG(bool, print_faulting_instruction, false,
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thurstond wrote:

We envision an Msan Compiler-rt Universe of runtime options:
- this patch: `print_faulting_instruction`
- future work?: `ignore_faulting_instruction` (for example, skip over all Vector Convert Half-word Unsigned to Long Unsigned [VCVTHULU] instructions)
- etc.

A user will be able to pick and choose any of these options at runtime, assuming the binary is already compiled with the embedded instruction.

https://github.com/llvm/llvm-project/pull/136539