Refactor the machine code emitter interface to pull the pointers for the current

code emission location into the base class, instead of being in the derived classes.

This change means that low-level methods like emitByte/emitWord now are no longer
virtual (yaay for speed), and we now have a framework to support growable code
segments.  This implements feature request #1 of PR469.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@28059 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 31 insertions, 52 deletions

diff --git a/lib/ExecutionEngine/JIT/JITEmitter.cpp b/lib/ExecutionEngine/JIT/JITEmitter.cpp
index cbe8f7af55..108b6b8583 100644
--- a/lib/ExecutionEngine/JIT/JITEmitter.cpp
+++ b/lib/ExecutionEngine/JIT/JITEmitter.cpp
@@ -413,13 +413,9 @@ namespace {
   class JITEmitter : public MachineCodeEmitter {
     JITMemoryManager MemMgr;
 
-    // CurBlock - The start of the current block of memory.  CurByte - The
-    // current byte being emitted to.
-    unsigned char *CurBlock, *CurByte;
-
     // When outputting a function stub in the context of some other function, we
-    // save CurBlock and CurByte here.
-    unsigned char *SavedCurBlock, *SavedCurByte;
+    // save BufferBegin/BufferEnd/CurBufferPtr here.
+    unsigned char *SavedBufferBegin, *SavedBufferEnd, *SavedCurBufferPtr;
 
     /// Relocations - These are the relocations that the function needs, as
     /// emitted.
@@ -449,22 +445,18 @@ public:
     }
 
     virtual void startFunction(MachineFunction &F);
-    virtual void finishFunction(MachineFunction &F);
+    virtual bool finishFunction(MachineFunction &F);
     virtual void emitConstantPool(MachineConstantPool *MCP);
     virtual void initJumpTableInfo(MachineJumpTableInfo *MJTI);
     virtual void emitJumpTableInfo(MachineJumpTableInfo *MJTI,
                                    std::map<MachineBasicBlock*,uint64_t> &MBBM);
     virtual void startFunctionStub(unsigned StubSize);
     virtual void* finishFunctionStub(const Function *F);
-    virtual void emitByte(unsigned char B);
-    virtual void emitWord(unsigned W);
 
     virtual void addRelocation(const MachineRelocation &MR) {
       Relocations.push_back(MR);
     }
 
-    virtual uint64_t getCurrentPCValue();
-    virtual uint64_t getCurrentPCOffset();
     virtual uint64_t getConstantPoolEntryAddress(unsigned Entry);
     virtual uint64_t getJumpTableEntryAddress(unsigned Entry);
     virtual unsigned char* allocateGlobal(unsigned size, unsigned alignment);
@@ -511,13 +503,16 @@ void *JITEmitter::getPointerToGlobal(GlobalValue *V, void *Reference,
 }
 
 void JITEmitter::startFunction(MachineFunction &F) {
-  CurByte = CurBlock = MemMgr.startFunctionBody();
-  TheJIT->addGlobalMapping(F.getFunction(), CurBlock);
+  BufferBegin = CurBufferPtr = MemMgr.startFunctionBody();
+  TheJIT->updateGlobalMapping(F.getFunction(), BufferBegin);
+  
+  /// FIXME: implement out of space handling correctly!
+  BufferEnd = (unsigned char*)(intptr_t)~0ULL;
 }
 
-void JITEmitter::finishFunction(MachineFunction &F) {
-  MemMgr.endFunctionBody(CurByte);
-  NumBytes += CurByte-CurBlock;
+bool JITEmitter::finishFunction(MachineFunction &F) {
+  MemMgr.endFunctionBody(CurBufferPtr);
+  NumBytes += getCurrentPCOffset();
 
   if (!Relocations.empty()) {
     NumRelos += Relocations.size();
@@ -534,7 +529,7 @@ void JITEmitter::finishFunction(MachineFunction &F) {
           ResultPtr = getJITResolver(this).getExternalFunctionStub(ResultPtr);
       } else if (MR.isGlobalValue())
         ResultPtr = getPointerToGlobal(MR.getGlobalValue(),
-                                       CurBlock+MR.getMachineCodeOffset(),
+                                       BufferBegin+MR.getMachineCodeOffset(),
                                        MR.doesntNeedFunctionStub());
       else //ConstantPoolIndex
         ResultPtr =
@@ -557,25 +552,26 @@ void JITEmitter::finishFunction(MachineFunction &F) {
       }
     }
 
-    TheJIT->getJITInfo().relocate(CurBlock, &Relocations[0],
+    TheJIT->getJITInfo().relocate(BufferBegin, &Relocations[0],
                                   Relocations.size(), MemMgr.getGOTBase());
   }
 
   //Update the GOT entry for F to point to the new code.
   if(MemMgr.isManagingGOT()) {
-    unsigned idx = getJITResolver(this).getGOTIndexForAddr((void*)CurBlock);
-    if (((void**)MemMgr.getGOTBase())[idx] != (void*)CurBlock) {
-      DEBUG(std::cerr << "GOT was out of date for " << (void*)CurBlock
+    unsigned idx = getJITResolver(this).getGOTIndexForAddr((void*)BufferBegin);
+    if (((void**)MemMgr.getGOTBase())[idx] != (void*)BufferBegin) {
+      DEBUG(std::cerr << "GOT was out of date for " << (void*)BufferBegin
             << " pointing at " << ((void**)MemMgr.getGOTBase())[idx] << "\n");
-      ((void**)MemMgr.getGOTBase())[idx] = (void*)CurBlock;
+      ((void**)MemMgr.getGOTBase())[idx] = (void*)BufferBegin;
     }
   }
 
-  DEBUG(std::cerr << "JIT: Finished CodeGen of [" << (void*)CurBlock
+  DEBUG(std::cerr << "JIT: Finished CodeGen of [" << (void*)BufferBegin
                   << "] Function: " << F.getFunction()->getName()
-                  << ": " << CurByte-CurBlock << " bytes of text, "
+                  << ": " << getCurrentPCOffset() << " bytes of text, "
                   << Relocations.size() << " relocations\n");
   Relocations.clear();
+  return false;
 }
 
 void JITEmitter::emitConstantPool(MachineConstantPool *MCP) {
@@ -648,26 +644,20 @@ void JITEmitter::emitJumpTableInfo(MachineJumpTableInfo *MJTI,
 }
 
 void JITEmitter::startFunctionStub(unsigned StubSize) {
-  SavedCurBlock = CurBlock;  SavedCurByte = CurByte;
-  CurByte = CurBlock = MemMgr.allocateStub(StubSize);
+  SavedBufferBegin = BufferBegin;
+  SavedBufferEnd = BufferEnd;
+  SavedCurBufferPtr = CurBufferPtr;
+  
+  BufferBegin = CurBufferPtr = MemMgr.allocateStub(StubSize);
+  BufferEnd = BufferBegin+StubSize+1;
 }
 
 void *JITEmitter::finishFunctionStub(const Function *F) {
-  NumBytes += CurByte-CurBlock;
-  std::swap(CurBlock, SavedCurBlock);
-  CurByte = SavedCurByte;
-  return SavedCurBlock;
-}
-
-void JITEmitter::emitByte(unsigned char B) {
-  *CurByte++ = B;   // Write the byte to memory
-}
-
-void JITEmitter::emitWord(unsigned W) {
-  // This won't work if the endianness of the host and target don't agree!  (For
-  // a JIT this can't happen though.  :)
-  *(unsigned*)CurByte = W;
-  CurByte += sizeof(unsigned);
+  NumBytes += getCurrentPCOffset();
+  std::swap(SavedBufferBegin, BufferBegin);
+  BufferEnd = SavedBufferEnd;
+  CurBufferPtr = SavedCurBufferPtr;
+  return SavedBufferBegin;
 }
 
 // getConstantPoolEntryAddress - Return the address of the 'ConstantNum' entry
@@ -702,17 +692,6 @@ unsigned char* JITEmitter::allocateGlobal(unsigned size, unsigned alignment)
   return MemMgr.allocateGlobal(size, alignment);
 }
 
-// getCurrentPCValue - This returns the address that the next emitted byte
-// will be output to.
-//
-uint64_t JITEmitter::getCurrentPCValue() {
-  return (intptr_t)CurByte;
-}
-
-uint64_t JITEmitter::getCurrentPCOffset() {
-  return (intptr_t)CurByte-(intptr_t)CurBlock;
-}
-
 // getPointerToNamedFunction - This function is used as a global wrapper to
 // JIT::getPointerToNamedFunction for the purpose of resolving symbols when
 // bugpoint is debugging the JIT. In that scenario, we are loading an .so and