Make the __morestack function available to the JIT memory manager under Linux.

[pcc]

Summary

This function's implementation lives in libgcc, a static library, so we need
to expose it explicitly, like the other such functions.

[reames]

LGTM - If you can, include the appropriate header, but you can submit either way. That's extremely minor.

lib/ExecutionEngine/RTDyldMemoryManager.cpp

215 ↗

(On Diff #17658)

Why do we need to forward declare this function, but not the other glibc functions used in getSymbolAddressInProccess? Is there a header we could include instead?

[pcc]

lib/ExecutionEngine/RTDyldMemoryManager.cpp

215 ↗

(On Diff #17658)

This function has a non-standard calling convention, so as far as I know there is no header we can include.

llvm/trunk/lib/ExecutionEngine/RTDyldMemoryManager.cpp

 // ARM_MATH_IMPORTS, but it doesn't matter because only the symbol addresses are
 // needed. In particular the __aeabi_*divmod functions do not have calling
 // conventions which match any C prototype.
 #define ARM_MATH_DECL(name) extern "C" void name();
 ARM_MATH_IMPORTS(ARM_MATH_DECL)
 #undef ARM_MATH_DECL
 #endif
 
+#if defined(__linux__) && defined(__GLIBC__)
+extern "C" void __morestack();
+#endif
+
 uint64_t
 RTDyldMemoryManager::getSymbolAddressInProcess(const std::string &Name) {
   // This implementation assumes that the host program is the target.
   // Clients generating code for a remote target should implement their own
   // memory manager.
 #if defined(__linux__) && defined(__GLIBC__)
   //===--------------------------------------------------------------------===//
   // Function stubs that are invoked instead of certain library calls
   //
   // Force the following functions to be linked in to anything that uses the
   // JIT. This is a hack designed to work around the all-too-clever Glibc
   // strategy of making these functions work differently when inlined vs. when
   // not inlined, and hiding their real definitions in a separate archive file
   // that the dynamic linker can't see. For more info, search for
   // 'libc_nonshared.a' on Google, or read http://llvm.org/PR274.
   if (Name == "stat") return (uint64_t)&stat;
   if (Name == "fstat") return (uint64_t)&fstat;
   if (Name == "lstat") return (uint64_t)&lstat;
   if (Name == "stat64") return (uint64_t)&stat64;
   if (Name == "fstat64") return (uint64_t)&fstat64;
   if (Name == "lstat64") return (uint64_t)&lstat64;
   if (Name == "atexit") return (uint64_t)&atexit;
   if (Name == "mknod") return (uint64_t)&mknod;
+
+  // __morestack lives in libgcc, a static library.
+  if (Name == "__morestack") return (uint64_t)&__morestack;
 #endif // __linux__ && __GLIBC__
   
   // See ARM_MATH_IMPORTS definition for explanation
 #if defined(__BIONIC__) && defined(__arm__)
   if (Name.compare(0, 8, "__aeabi_") == 0) {
     // Check if the user has requested any of the functions listed in
     // ARM_MATH_IMPORTS, and if so redirect to the statically linked symbol.
 #define ARM_MATH_CHECK(fn) if (Name == #fn) return (uint64_t)&fn;