[sancov] Add SPARC support for getPreviousInstructionPc.

[XiaodongLoong]

Summary

The SPARC and MIPS branching operations have a branch delay slot, 4 more bytes occupied.

Depends on D120381

[ro]

The patch looks sensible, but isn't actually exercised: I ran a sparcv9-sun-solaris2.11 build with it included, which made no difference. However, on closer inspection, the sanitizer_coverage_trace_pc_guard*.cpp tests didn't run: they aren't supported together with ubsan, while asan isn't supported on SPARC due to a clang bug/limitation.

That said, the patch is plausible, so LGTM.

llvm/tools/sancov/sancov.cpp

 
 // Ported from
 // compiler-rt/lib/sanitizer_common/sanitizer_stacktrace.h:GetPreviousInstructionPc
 // GetPreviousInstructionPc.
 static uint64_t getPreviousInstructionPc(uint64_t PC,
                                          Triple TheTriple) {
   if (TheTriple.isARM())
     return (PC - 3) & (~1);
-  if (TheTriple.isMIPS())
+  if (TheTriple.isMIPS() || TheTriple.isSPARC())
     return PC - 8;
   if (TheTriple.isRISCV())
     return PC - 2;
   if (TheTriple.isX86() || TheTriple.isSystemZ())
     return PC - 1;
   return PC - 4;
 }