[clang] [llvm] Add support for Windows hot-patching (PR #138972)

[Alexandre Ganea via cfe-commits]

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@@ -453,6 +453,37 @@ CodeGenModule::CodeGenModule(ASTContext &C,
   if (Context.getTargetInfo().getTriple().getArch() == llvm::Triple::x86)
     getModule().addModuleFlag(llvm::Module::Error, "NumRegisterParameters",
                               CodeGenOpts.NumRegisterParameters);
+
+  // If there are any functions that are marked for Windows hot-patching,
+  // then build the list of functions now.
+  if (!CGO.MSHotPatchFunctionsFile.empty() ||
+      !CGO.MSHotPatchFunctionsList.empty()) {
+    if (!CGO.MSHotPatchFunctionsFile.empty()) {
+      auto BufOrErr = llvm::MemoryBuffer::getFile(CGO.MSHotPatchFunctionsFile);
+      if (BufOrErr) {
+        const llvm::MemoryBuffer &FileBuffer = **BufOrErr;
+        for (llvm::line_iterator I(FileBuffer.getMemBufferRef(), true), E;
+             I != E; ++I) {
+          this->MSHotPatchFunctions.push_back(std::string{*I});
+        }
+      } else {
+        auto &DE = Context.getDiagnostics();
+        unsigned DiagID =
+            DE.getCustomDiagID(DiagnosticsEngine::Error,
+                               "failed to open hotpatch functions file "
+                               "(-fms-hotpatch-functions-file): %0 : %1");
+        DE.Report(DiagID) << CGO.MSHotPatchFunctionsFile
+                          << BufOrErr.getError().message();
+      }
+    }
+
+    for (const auto &FuncName : CGO.MSHotPatchFunctionsList) {
----------------
aganea wrote:

LLVM coding standards [instructs](https://llvm.org/docs/CodingStandards.html#don-t-use-braces-on-simple-single-statement-bodies-of-if-else-loop-statements) to omit braces for one liners, but TBH I prefer the Rust rule where the brace should always be mandatory. What do other reviewers think?

https://github.com/llvm/llvm-project/pull/138972