Introduce a native-only unwinder build.

Currently libunwind is built to support cross-unwinding [1] by default, which
requires the buffers unw_context_t and unw_cursor_t to be large enough to hold
the vritual register set (VRS) of any supported architecture. This is not
desirable for some platforms where the stack usage of the unwinder needs
to be kept to a minimum (e.g. bare-metal targets). The current patch introduces
a native-only (-DLIBUNWIND_ENABLE_CROSS_UNWINDING=OFF) unwinder variant that
adopts strict sizes for the buffers unw_context_t and unw_cursor_t depending
on the target architecture.

[1] http://www.nongnu.org/libunwind/man/libunwind(3).html#section_4

Change-Id: I380fff9a56c16a0fc520e3b1d8454a34b4a48373
llvm-svn: 270692

1 files changed, 27 insertions, 1 deletions

diff --git a/libunwind/src/UnwindCursor.hpp b/libunwind/src/UnwindCursor.hpp
index 90683164ff2..661ef4a264c 100644
--- a/libunwind/src/UnwindCursor.hpp
+++ b/libunwind/src/UnwindCursor.hpp
@@ -481,30 +481,39 @@ private:
     return stepWithCompactEncoding(dummy);
   }
 
+#if defined(_LIBUNWIND_TARGET_X86_64)
   int stepWithCompactEncoding(Registers_x86_64 &) {
     return CompactUnwinder_x86_64<A>::stepWithCompactEncoding(
         _info.format, _info.start_ip, _addressSpace, _registers);
   }
+#endif
 
+#if defined(_LIBUNWIND_TARGET_I386)
   int stepWithCompactEncoding(Registers_x86 &) {
     return CompactUnwinder_x86<A>::stepWithCompactEncoding(
         _info.format, (uint32_t)_info.start_ip, _addressSpace, _registers);
   }
+#endif
 
+#if defined(_LIBUNWIND_TARGET_PPC)
   int stepWithCompactEncoding(Registers_ppc &) {
     return UNW_EINVAL;
   }
+#endif
 
+#if defined(_LIBUNWIND_TARGET_AARCH64)
   int stepWithCompactEncoding(Registers_arm64 &) {
     return CompactUnwinder_arm64<A>::stepWithCompactEncoding(
         _info.format, _info.start_ip, _addressSpace, _registers);
   }
+#endif
 
   bool compactSaysUseDwarf(uint32_t *offset=NULL) const {
     R dummy;
     return compactSaysUseDwarf(dummy, offset);
   }
 
+#if defined(_LIBUNWIND_TARGET_X86_64)
   bool compactSaysUseDwarf(Registers_x86_64 &, uint32_t *offset) const {
     if ((_info.format & UNWIND_X86_64_MODE_MASK) == UNWIND_X86_64_MODE_DWARF) {
       if (offset)
@@ -513,7 +522,9 @@ private:
     }
     return false;
   }
+#endif
 
+#if defined(_LIBUNWIND_TARGET_I386)
   bool compactSaysUseDwarf(Registers_x86 &, uint32_t *offset) const {
     if ((_info.format & UNWIND_X86_MODE_MASK) == UNWIND_X86_MODE_DWARF) {
       if (offset)
@@ -522,11 +533,15 @@ private:
     }
     return false;
   }
+#endif
 
+#if defined(_LIBUNWIND_TARGET_PPC)
   bool compactSaysUseDwarf(Registers_ppc &, uint32_t *) const {
     return true;
   }
+#endif
 
+#if defined(_LIBUNWIND_TARGET_AARCH64)
   bool compactSaysUseDwarf(Registers_arm64 &, uint32_t *offset) const {
     if ((_info.format & UNWIND_ARM64_MODE_MASK) == UNWIND_ARM64_MODE_DWARF) {
       if (offset)
@@ -535,6 +550,7 @@ private:
     }
     return false;
   }
+#endif
 #endif // _LIBUNWIND_SUPPORT_COMPACT_UNWIND
 
 #if _LIBUNWIND_SUPPORT_DWARF_UNWIND
@@ -543,25 +559,35 @@ private:
     return dwarfEncoding(dummy);
   }
 
+#if defined(_LIBUNWIND_TARGET_X86_64)
   compact_unwind_encoding_t dwarfEncoding(Registers_x86_64 &) const {
     return UNWIND_X86_64_MODE_DWARF;
   }
+#endif
 
+#if defined(_LIBUNWIND_TARGET_I386)
   compact_unwind_encoding_t dwarfEncoding(Registers_x86 &) const {
     return UNWIND_X86_MODE_DWARF;
   }
+#endif
 
+#if defined(_LIBUNWIND_TARGET_PPC)
   compact_unwind_encoding_t dwarfEncoding(Registers_ppc &) const {
     return 0;
   }
+#endif
 
+#if defined(_LIBUNWIND_TARGET_AARCH64)
   compact_unwind_encoding_t dwarfEncoding(Registers_arm64 &) const {
     return UNWIND_ARM64_MODE_DWARF;
   }
+#endif
 
+#if defined (_LIBUNWIND_TARGET_OR1K)
   compact_unwind_encoding_t dwarfEncoding(Registers_or1k &) const {
     return 0;
   }
+#endif
 #endif // _LIBUNWIND_SUPPORT_DWARF_UNWIND
 
 
@@ -577,7 +603,7 @@ template <typename A, typename R>
 UnwindCursor<A, R>::UnwindCursor(unw_context_t *context, A &as)
     : _addressSpace(as), _registers(context), _unwindInfoMissing(false),
       _isSignalFrame(false) {
-  static_assert(sizeof(UnwindCursor<A, R>) < sizeof(unw_cursor_t),
+  static_assert(check_fit<UnwindCursor<A, R>, unw_cursor_t>::does_fit,
                 "UnwindCursor<> does not fit in unw_cursor_t");
   memset(&_info, 0, sizeof(_info));
 }