Add a custom safepoint method, in order for language implementers to decide which machine instruction gets to be a safepoint.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@144399 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/CodeGen/GCStrategy.h

@@ -37,6 +37,7 @@
 #define LLVM_CODEGEN_GCSTRATEGY_H
 
 #include "llvm/CodeGen/GCMetadata.h"
+#include "llvm/CodeGen/MachineFunction.h"
 #include "llvm/Support/Registry.h"
 #include <string>
 
@@ -68,6 +69,8 @@ namespace llvm {
     bool CustomReadBarriers;   //< Default is to insert loads.
     bool CustomWriteBarriers;  //< Default is to insert stores.
     bool CustomRoots;          //< Default is to pass through to backend.
+    bool CustomSafePoints;     //< Default is to use NeededSafePoints
+                               //  to find safe points.
     bool InitRoots;            //< If set, roots are nulled during lowering.
     bool UsesMetadata;         //< If set, backend must emit metadata tables.
     
@@ -87,7 +90,9 @@ namespace llvm {
 
     /// needsSafePoitns - True if safe points of any kind are required. By
     //                    default, none are recorded.
-    bool needsSafePoints() const { return NeededSafePoints != 0; }
+    bool needsSafePoints() const {
+      return CustomSafePoints || NeededSafePoints != 0;
+    }
     
     /// needsSafePoint(Kind) - True if the given kind of safe point is
     //                          required. By default, none are recorded.
@@ -110,6 +115,11 @@ namespace llvm {
     //                performCustomLowering must delete them.
     bool customRoots() const { return CustomRoots; }
 
+    /// customSafePoints - By default, the GC analysis will find safe
+    ///                    points according to NeededSafePoints. If true,
+    ///                    then findCustomSafePoints must create them.
+    bool customSafePoints() const { return CustomSafePoints; }
+    
     /// initializeRoots - If set, gcroot intrinsics should initialize their
     //                    allocas to null before the first use. This is
     //                    necessary for most GCs and is enabled by default.
@@ -135,6 +145,7 @@ namespace llvm {
     /// which the LLVM IR can be modified.
     virtual bool initializeCustomLowering(Module &F);
     virtual bool performCustomLowering(Function &F);
+    virtual bool findCustomSafePoints(GCFunctionInfo& FI, MachineFunction& MF);
   };
   
 }

lib/CodeGen/GCStrategy.cpp

@@ -97,6 +97,7 @@ GCStrategy::GCStrategy() :
   CustomReadBarriers(false),
   CustomWriteBarriers(false),
   CustomRoots(false),
+  CustomSafePoints(false),
   InitRoots(true),
   UsesMetadata(false)
 {}
@@ -116,6 +117,14 @@ bool GCStrategy::performCustomLowering(Function &F) {
   return 0;
 }
 
+
+bool GCStrategy::findCustomSafePoints(GCFunctionInfo& FI, MachineFunction &F) {
+  dbgs() << "gc " << getName() << " must override findCustomSafePoints.\n";
+  llvm_unreachable(0);
+  return 0;
+}
+
+
 GCFunctionInfo *GCStrategy::insertFunctionInfo(const Function &F) {
   GCFunctionInfo *FI = new GCFunctionInfo(F, *this);
   Functions.push_back(FI);
@@ -407,7 +416,11 @@ bool MachineCodeAnalysis::runOnMachineFunction(MachineFunction &MF) {
   FI->setFrameSize(MF.getFrameInfo()->getStackSize());
 
   // Find all safe points.
+  if (FI->getStrategy().customSafePoints()) {
+    FI->getStrategy().findCustomSafePoints(*FI, MF);
+  } else {
     FindSafePoints(MF);
+  }
   
   // Find the stack offsets for all roots.
   FindStackOffsets(MF);