[llvm] Add option to dump IR to files intstead of stderr (PR #66412)

[Matt Arsenault via llvm-commits]

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@@ -55,6 +55,10 @@ bool forcePrintModuleIR();
 bool isPassInPrintList(StringRef PassName);
 bool isFilterPassesEmpty();
 
+// Returns a non-empty string if printing before/after passes is to be
+// dumped into files in the returned directory instead of written to stderr.
+std::string irDumpDirectory();
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arsenm wrote:

This can just return StringRef

https://github.com/llvm/llvm-project/pull/66412