[llvm-commits] CVS: llvm/tools/lli/JIT/Emitter.cpp
Chris Lattner
lattner at cs.uiuc.edu
Thu Aug 14 13:36:00 PDT 2003
Changes in directory llvm/tools/lli/JIT:
Emitter.cpp updated: 1.22 -> 1.23
---
Log message:
Implement a _REAL_ memory manager for the code generated by the JIT. This
speeds up program execution by 15% pretty consistently for large programs
---
Diffs of the changes:
Index: llvm/tools/lli/JIT/Emitter.cpp
diff -u llvm/tools/lli/JIT/Emitter.cpp:1.22 llvm/tools/lli/JIT/Emitter.cpp:1.23
--- llvm/tools/lli/JIT/Emitter.cpp:1.22 Tue Aug 5 12:00:32 2003
+++ llvm/tools/lli/JIT/Emitter.cpp Thu Aug 14 13:35:27 2003
@@ -21,7 +21,102 @@
Statistic<> NumBytes("jello", "Number of bytes of machine code compiled");
VM *TheVM = 0;
+ /// JITMemoryManager - Manage memory for the JIT code generation in a logical,
+ /// sane way. This splits a large block of MAP_NORESERVE'd memory into two
+ /// sections, one for function stubs, one for the functions themselves. We
+ /// have to do this because we may need to emit a function stub while in the
+ /// middle of emitting a function, and we don't know how large the function we
+ /// are emitting is. This never bothers to release the memory, because when
+ /// we are ready to destroy the JIT, the program exits.
+ class JITMemoryManager {
+ unsigned char *MemBase; // Base of block of memory, start of stub mem
+ unsigned char *FunctionBase; // Start of the function body area
+ unsigned char *CurStubPtr, *CurFunctionPtr;
+ public:
+ JITMemoryManager();
+
+ inline unsigned char *allocateStub(unsigned StubSize);
+ inline unsigned char *startFunctionBody();
+ inline void endFunctionBody(unsigned char *FunctionEnd);
+ };
+}
+
+#define _POSIX_MAPPED_FILES
+#include <unistd.h>
+#include <sys/mman.h>
+
+// getMemory - Return a pointer to the specified number of bytes, which is
+// mapped as executable readable and writable.
+static void *getMemory(unsigned NumBytes) {
+ if (NumBytes == 0) return 0;
+ static const long pageSize = sysconf(_SC_PAGESIZE);
+ unsigned NumPages = (NumBytes+pageSize-1)/pageSize;
+
+#if defined(i386) || defined(__i386__) || defined(__x86__)
+ /* Linux and *BSD tend to have these flags named differently. */
+#if defined(MAP_ANON) && !defined(MAP_ANONYMOUS)
+# define MAP_ANONYMOUS MAP_ANON
+#endif /* defined(MAP_ANON) && !defined(MAP_ANONYMOUS) */
+#define fd 0
+#elif defined(sparc) || defined(__sparc__) || defined(__sparcv9)
+#define fd -1
+#else
+ std::cerr << "This architecture is not supported by the JIT!\n";
+ abort();
+#endif
+
+ unsigned mmapFlags = MAP_PRIVATE|MAP_ANONYMOUS;
+#ifdef MAP_NORESERVE
+ mmapFlags |= MAP_NORESERVE;
+#endif
+
+ void *pa = mmap(0, pageSize*NumPages, PROT_READ|PROT_WRITE|PROT_EXEC,
+ MAP_PRIVATE|MAP_ANONYMOUS, fd, 0);
+ if (pa == MAP_FAILED) {
+ perror("mmap");
+ abort();
+ }
+ return pa;
+}
+
+JITMemoryManager::JITMemoryManager() {
+ // Allocate a 16M block of memory...
+ MemBase = (unsigned char*)getMemory(16 << 20);
+ FunctionBase = MemBase + 512*1024; // Use 512k for stubs
+
+ // Allocate stubs backwards from the function base, allocate functions forward
+ // from the function base.
+ CurStubPtr = CurFunctionPtr = FunctionBase;
+}
+
+unsigned char *JITMemoryManager::allocateStub(unsigned StubSize) {
+ CurStubPtr -= StubSize;
+ if (CurStubPtr < MemBase) {
+ std::cerr << "JIT ran out of memory for function stubs!\n";
+ abort();
+ }
+ return CurStubPtr;
+}
+
+unsigned char *JITMemoryManager::startFunctionBody() {
+ // Round up to an even multiple of 4 bytes, this should eventually be target
+ // specific.
+ return (unsigned char*)(((intptr_t)CurFunctionPtr + 3) & ~3);
+}
+
+void JITMemoryManager::endFunctionBody(unsigned char *FunctionEnd) {
+ assert(FunctionEnd > CurFunctionPtr);
+ CurFunctionPtr = FunctionEnd;
+}
+
+
+
+namespace {
+ /// Emitter - The JIT implementation of the MachineCodeEmiter, which is used
+ /// to output functions to memory for execution.
class Emitter : public MachineCodeEmitter {
+ JITMemoryManager MemMgr;
+
// CurBlock - The start of the current block of memory. CurByte - The
// current byte being emitted to.
unsigned char *CurBlock, *CurByte;
@@ -62,47 +157,13 @@
return new Emitter(V);
}
-
-#define _POSIX_MAPPED_FILES
-#include <unistd.h>
-#include <sys/mman.h>
-
-// FIXME: This should be rewritten to support a real memory manager for
-// executable memory pages!
-static void *getMemory(unsigned NumPages) {
- void *pa;
- if (NumPages == 0) return 0;
- static const long pageSize = sysconf(_SC_PAGESIZE);
-
-#if defined(i386) || defined(__i386__) || defined(__x86__)
- /* Linux and *BSD tend to have these flags named differently. */
-#if defined(MAP_ANON) && !defined(MAP_ANONYMOUS)
-# define MAP_ANONYMOUS MAP_ANON
-#endif /* defined(MAP_ANON) && !defined(MAP_ANONYMOUS) */
-#define fd 0
-#elif defined(sparc) || defined(__sparc__) || defined(__sparcv9)
-#define fd -1
-#else
- std::cerr << "This architecture is not supported by the JIT!\n";
- abort();
-#endif
- pa = mmap(0, pageSize*NumPages, PROT_READ|PROT_WRITE|PROT_EXEC,
- MAP_PRIVATE|MAP_ANONYMOUS, fd, 0);
- if (pa == MAP_FAILED) {
- perror("mmap");
- abort();
- }
- return pa;
-}
-
-
void Emitter::startFunction(MachineFunction &F) {
- CurBlock = (unsigned char *)getMemory(16);
- CurByte = CurBlock; // Start writing at the beginning of the fn.
+ CurByte = CurBlock = MemMgr.startFunctionBody();
TheVM->addGlobalMapping(F.getFunction(), CurBlock);
}
void Emitter::finishFunction(MachineFunction &F) {
+ MemMgr.endFunctionBody(CurByte);
ConstantPoolAddresses.clear();
NumBytes += CurByte-CurBlock;
@@ -124,11 +185,8 @@
}
void Emitter::startFunctionStub(const Function &F, unsigned StubSize) {
- static const long pageSize = sysconf(_SC_PAGESIZE);
SavedCurBlock = CurBlock; SavedCurByte = CurByte;
- // FIXME: this is a huge waste of memory.
- CurBlock = (unsigned char *)getMemory((StubSize+pageSize-1)/pageSize);
- CurByte = CurBlock; // Start writing at the beginning of the fn.
+ CurByte = CurBlock = MemMgr.allocateStub(StubSize);
}
void *Emitter::finishFunctionStub(const Function &F) {
@@ -147,8 +205,8 @@
}
void Emitter::emitWord(unsigned W) {
- // FIXME: This won't work if the endianness of the host and target don't
- // agree! (For a JIT this can't happen though. :)
+ // 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);
}
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