Add control point patching pass.

This change adds a LLVM pass which replaces a call to a dummy control
(`yk_control_point`) point with a call to a dynamically generated
control point (`yk_new_control_point`) containing all of the necessary
logic to start and stop tracing, and to jump to machine code etc.

The logic is *very* simplified for now, but this should be a good
starting point.

In order for LLVM to not optimise away some of the control point logic
(e.g. the IOStruct) this pass has to run very late in the pipeline.

The pass is also only enabled when `--yk-patch-control-point` is passed.

See the comment at the top of ControlPoint.cpp for more details.

Co-authored-by: Edd Barrett <vext01@gmail.com>

Author: ptersilie

.buildbot.sh

@@ -21,6 +21,11 @@ make -j `nproc` install
 make -j `nproc` check-all
 cd ..
 
+# clang-format any new files that we've introduced ourselves.
+PATH=${INST_DIR}/bin:${PATH}
+sh yk_format_new_files.sh
+git diff --exit-code
+
 # FIXME The commented code below should run the `test-suite` tests, as
 # described at https://llvm.org/docs/TestSuiteGuide.html.
 #

llvm/include/llvm/Transforms/Yk/ControlPoint.h

@@ -0,0 +1,18 @@
+#ifndef LLVM_TRANSFORMS_YK_CONTROLPOINT_H
+#define LLVM_TRANSFORMS_YK_CONTROLPOINT_H
+
+#include "llvm/IR/PassManager.h"
+
+// The name of the "dummy function" that the user puts in their interpreter
+// implementation and that we will replace with our own code.
+#define YK_DUMMY_CONTROL_POINT "yk_control_point"
+
+// The name of the new control point replacing the user's dummy control point.
+#define YK_NEW_CONTROL_POINT "yk_new_control_point"
+
+namespace llvm {
+class ModulePass;
+ModulePass *createYkControlPointPass();
+} // namespace llvm
+
+#endif

llvm/lib/CodeGen/CMakeLists.txt

@@ -216,6 +216,7 @@ add_llvm_component_library(LLVMCodeGen
   Support
   Target
   TransformUtils
+  YkControlPoint
   )
 
 add_subdirectory(SelectionDAG)

llvm/lib/Passes/CMakeLists.txt

@@ -25,4 +25,5 @@ add_llvm_component_library(LLVMPasses
   TransformUtils
   Vectorize
   Instrumentation
+  YkControlPoint
   )

llvm/lib/Transforms/CMakeLists.txt

@@ -9,3 +9,4 @@ add_subdirectory(Hello)
 add_subdirectory(ObjCARC)
 add_subdirectory(Coroutines)
 add_subdirectory(CFGuard)
+add_subdirectory(Yk)

llvm/lib/Transforms/IPO/CMakeLists.txt

@@ -71,4 +71,5 @@ add_llvm_component_library(LLVMipo
   TransformUtils
   Vectorize
   Instrumentation
+  YkControlPoint
   )

llvm/lib/Transforms/IPO/PassManagerBuilder.cpp

@@ -51,6 +51,7 @@
 #include "llvm/Transforms/Vectorize/LoopVectorize.h"
 #include "llvm/Transforms/Vectorize/SLPVectorizer.h"
 #include "llvm/Transforms/Vectorize/VectorCombine.h"
+#include "llvm/Transforms/Yk/ControlPoint.h"
 
 using namespace llvm;
 
@@ -188,6 +189,11 @@ cl::opt<AttributorRunOption> AttributorRun(
                clEnumValN(AttributorRunOption::NONE, "none",
                           "disable attributor runs")));
 
+static cl::opt<bool>
+YkPatchCtrlPoint("yk-patch-control-point",
+  cl::init(false), cl::NotHidden,
+  cl::desc("Patch yk_control_point()"));
+
 extern cl::opt<bool> EnableKnowledgeRetention;
 } // namespace llvm
 
@@ -1240,6 +1246,13 @@ void PassManagerBuilder::populateLTOPassManager(legacy::PassManagerBase &PM) {
 
   PM.add(createAnnotationRemarksLegacyPass());
 
+  // We add the yk control point pass late in the pipeline (after all
+  // optimisation and just before verification and codegen) so that no IR
+  // optimisation passes have a chance to change the interface to the control
+  // point. The JIT runtime relies on the signature not being changed.
+  if (YkPatchCtrlPoint)
+    PM.add(createYkControlPointPass());
+
   if (VerifyOutput)
     PM.add(createVerifierPass());
 }

llvm/lib/Transforms/Yk/CMakeLists.txt

@@ -0,0 +1,10 @@
+add_llvm_component_library(LLVMYkControlPoint
+  ControlPoint.cpp
+
+  DEPENDS
+  intrinsics_gen
+
+  LINK_COMPONENTS
+  Core
+  Support
+)