Add the yk-optnone-after-ir-passes command line option.

This is required to block backend optimisations when building an
intepreter with `-Xclang -disable-O0-optnone`.

Author: vext01

llvm/include/llvm/Support/Yk.h

@@ -5,4 +5,8 @@ namespace llvm {
 void initYkOptions(void);
 } // namespace llvm
 
+// YKFIXME: all of our command-line arguments should be collected here instead
+// of us randomly introducing `extern bool`s all over the place.
+extern bool YkOptNoneAfterIRPasses;
+
 #endif

llvm/lib/LTO/LTOBackend.cpp

@@ -39,6 +39,7 @@
 #include "llvm/Support/ThreadPool.h"
 #include "llvm/Support/ToolOutputFile.h"
 #include "llvm/Support/raw_ostream.h"
+#include "llvm/Support/Yk.h"
 #include "llvm/Target/TargetMachine.h"
 #include "llvm/Transforms/IPO/WholeProgramDevirt.h"
 #include "llvm/Transforms/Scalar/LoopPassManager.h"
@@ -509,6 +510,16 @@ Error lto::backend(const Config &C, AddStreamFn AddStream,
       return Error::success();
   }
 
+  // Yk can't tolerate backend optimisations, so we mark every function with
+  // `optnone` from here onwards.
+  if (YkOptNoneAfterIRPasses) {
+    for (Function &F: Mod) {
+      if (!F.isDeclaration()) {
+        F.addFnAttr(Attribute::OptimizeNone);
+      }
+    }
+  }
+
   if (ParallelCodeGenParallelismLevel == 1) {
     codegen(C, TM.get(), AddStream, 0, Mod, CombinedIndex);
   } else {

llvm/lib/Support/Yk.cpp

@@ -96,11 +96,27 @@ static ManagedStatic<cl::opt<bool, true>,
                      CreateYkStackmapsSpillReloadsFixParser>
     YkStackmapsSpillFixParser;
 
+bool YkOptNoneAfterIRPasses;
+namespace {
+struct CreateYkOptNoneAfterIRPassesParser {
+  static void *call() {
+    return new cl::opt<bool, true>(
+        "yk-optnone-after-ir-passes",
+        cl::desc(
+            "Apply `optnone` to all functions prior to instruction selection."),
+        cl::NotHidden, cl::location(YkOptNoneAfterIRPasses));
+  }
+};
+} // namespace
+static ManagedStatic<cl::opt<bool, true>,
+  CreateYkOptNoneAfterIRPassesParser> YkOptNoneAfterIRPassesParser;
+
 void llvm::initYkOptions() {
   *YkAllocLLVMBCSectionParser;
   *YkAllocLLVMBBAddrMapSectionParser;
   *YkExtendedLLVMBBAddrMapSectionParser;
   *YkStackMapOffsetFixParser;
   *YkStackMapAdditionalLocsParser;
   *YkStackmapsSpillFixParser;
+  *YkOptNoneAfterIRPassesParser;
 }