Do not make -pass-remarks additive.

[dnovillo]

Summary

When I initially introduced -pass-remarks, I thought it would be a
neat idea to make it additive. So, if one used it as:

$ llc -pass-remarks=inliner --pass-remarks=loop.*

the compiler would build the regular expression '(inliner)|(loop.*)'.

The more I think about it, the more I regret it. This is not how
other flags work. The standard semantics are right-to-left overrides.

This is how clang interprets -Rpass. And I think the two should be
compatible in this respect.

[qcolombet]

Hi Diego,

Although I liked it this way, your change makes sense.

If we decide to go back, that you be easy to resurrect the previous behavior.

LGTM with maybe a test case with two options and we check that we only emit what is related to the last one.

Thanks,

-Quentin

lib/IR/LLVMContextImpl.cpp

 namespace {
 
 /// \brief Regular expression corresponding to the value given in the
 /// command line flag -pass-remarks. Passes whose name matches this
 /// regexp will emit a diagnostic when calling
 /// LLVMContext::emitOptimizationRemark.
 static Regex *OptimizationRemarkPattern = nullptr;
 
-/// \brief String to hold all the values passed via -pass-remarks. Every
-/// instance of -pass-remarks on the command line will be concatenated
-/// to this string. Values are stored inside braces and concatenated with
-/// the '|' operator. This implements the expected semantics that multiple
-/// -pass-remarks are additive.
-static std::string OptimizationRemarkExpr;
-
 struct PassRemarksOpt {
   void operator=(const std::string &Val) const {
     // Create a regexp object to match pass names for emitOptimizationRemark.
     if (!Val.empty()) {
-      if (!OptimizationRemarkExpr.empty())
-        OptimizationRemarkExpr += "|";
-      OptimizationRemarkExpr += "(" + Val + ")";
       delete OptimizationRemarkPattern;
-      OptimizationRemarkPattern = new Regex(OptimizationRemarkExpr);
+      OptimizationRemarkPattern = new Regex(Val);
       std::string RegexError;
       if (!OptimizationRemarkPattern->isValid(RegexError))
         report_fatal_error("Invalid regular expression '" + Val +
                                "' in -pass-remarks: " + RegexError,
                            false);
     }
   };
 };