Add support for function stubs, which allow calling functions which need to
have an address available, but have not yet been code generated.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@6059 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/ExecutionEngine/JIT/JITEmitter.cpp b/lib/ExecutionEngine/JIT/JITEmitter.cpp
index 69e2453..f6f6b30 100644
--- a/lib/ExecutionEngine/JIT/JITEmitter.cpp
+++ b/lib/ExecutionEngine/JIT/JITEmitter.cpp
@@ -19,8 +19,11 @@
class Emitter : public MachineCodeEmitter {
VM &TheVM;
- unsigned char *CurBlock;
- unsigned char *CurByte;
+ 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;
std::vector<std::pair<BasicBlock*, unsigned *> > BBRefs;
std::map<BasicBlock*, unsigned> BBLocations;
@@ -32,6 +35,8 @@
virtual void finishFunction(MachineFunction &F);
virtual void emitConstantPool(MachineConstantPool *MCP);
virtual void startBasicBlock(MachineBasicBlock &BB);
+ virtual void startFunctionStub(const Function &F, unsigned StubSize);
+ virtual void* finishFunctionStub(const Function &F);
virtual void emitByte(unsigned char B);
virtual void emitPCRelativeDisp(Value *V);
virtual void emitGlobalAddress(GlobalValue *V, bool isPCRelative);
@@ -52,14 +57,16 @@
#include <unistd.h>
#include <sys/mman.h>
-static void *getMemory() {
- return mmap(0, 4096*8, PROT_READ|PROT_WRITE|PROT_EXEC,
+// FIXME: This should be rewritten to support a real memory manager for
+// executable memory pages!
+static void *getMemory(unsigned NumPages) {
+ return mmap(0, 4096*NumPages, PROT_READ|PROT_WRITE|PROT_EXEC,
MAP_PRIVATE|MAP_ANONYMOUS, 0, 0);
}
void Emitter::startFunction(MachineFunction &F) {
- CurBlock = (unsigned char *)getMemory();
+ CurBlock = (unsigned char *)getMemory(8);
CurByte = CurBlock; // Start writing at the beginning of the fn.
TheVM.addGlobalMapping(F.getFunction(), CurBlock);
}
@@ -100,6 +107,24 @@
}
+void Emitter::startFunctionStub(const Function &F, unsigned StubSize) {
+ SavedCurBlock = CurBlock; SavedCurByte = CurByte;
+ // FIXME: this is a huge waste of memory.
+ CurBlock = (unsigned char *)getMemory((StubSize+4095)/4096);
+ CurByte = CurBlock; // Start writing at the beginning of the fn.
+}
+
+void *Emitter::finishFunctionStub(const Function &F) {
+ NumBytes += CurByte-CurBlock;
+ DEBUG(std::cerr << "Finished CodeGen of [0x" << std::hex
+ << (unsigned)(intptr_t)CurBlock
+ << std::dec << "] Function stub for: " << F.getName()
+ << ": " << CurByte-CurBlock << " bytes of text\n");
+ std::swap(CurBlock, SavedCurBlock);
+ CurByte = SavedCurByte;
+ return SavedCurBlock;
+}
+
void Emitter::emitByte(unsigned char B) {
*CurByte++ = B; // Write the byte to memory
}