rmaprath created this revision.
rmaprath added a reviewer: jroelofs.
rmaprath added a subscriber: cfe-commits.
Herald added subscribers: rengolin, aemerson.
Currently, `unw_context_t` and `unw_cursor_t` are sized to allow the virtual
register set of any target supported by libunwind. This does not work well for
baremetal ARM targets (where memory is at a premium).
This patch makes `unw_context_t` and `unw_cursor_t` use just enough space to
hold the ARM virtual register set on baremetal arm targets.
The various `Registers_xxx` definitions (and their dependencies) had to be
conditionally compiled out in order to allow each of the targets to perform
size checks independently.
This change saves about 1500 bytes of stack on ARM v7 (similar amount on
AArch32).
http://reviews.llvm.org/D19920
Files:
include/libunwind.h
src/CompactUnwinder.hpp
src/Registers.hpp
src/UnwindCursor.hpp
src/libunwind.cpp
Index: src/libunwind.cpp
===================================================================
--- src/libunwind.cpp
+++ src/libunwind.cpp
@@ -45,30 +45,29 @@
_LIBUNWIND_TRACE_API("unw_init_local(cursor=%p, context=%p)\n",
static_cast<void *>(cursor),
static_cast<void *>(context));
- // Use "placement new" to allocate UnwindCursor in the cursor buffer.
#if defined(__i386__)
- new ((void *)cursor) UnwindCursor<LocalAddressSpace, Registers_x86>(
- context, LocalAddressSpace::sThisAddressSpace);
+# define REGISTER_KIND Registers_x86
#elif defined(__x86_64__)
- new ((void *)cursor) UnwindCursor<LocalAddressSpace, Registers_x86_64>(
- context, LocalAddressSpace::sThisAddressSpace);
+# define REGISTER_KIND Registers_x86_64
#elif defined(__ppc__)
- new ((void *)cursor) UnwindCursor<LocalAddressSpace, Registers_ppc>(
- context, LocalAddressSpace::sThisAddressSpace);
+# define REGISTER_KIND Registers_ppc
#elif defined(__arm64__) || defined(__aarch64__)
- new ((void *)cursor) UnwindCursor<LocalAddressSpace, Registers_arm64>(
- context, LocalAddressSpace::sThisAddressSpace);
+# define REGISTER_KIND Registers_arm64
#elif _LIBUNWIND_ARM_EHABI
- new ((void *)cursor) UnwindCursor<LocalAddressSpace, Registers_arm>(
- context, LocalAddressSpace::sThisAddressSpace);
+# define REGISTER_KIND Registers_arm
#elif defined(__or1k__)
- new ((void *)cursor) UnwindCursor<LocalAddressSpace, Registers_or1k>(
- context, LocalAddressSpace::sThisAddressSpace);
+# define REGISTER_KIND Registers_or1k
#elif defined(__mips__)
-#warning The MIPS architecture is not supported.
+# warning The MIPS architecture is not supported.
#else
-#error Architecture not supported
+# error Architecture not supported
#endif
+ static_assert(sizeof(UnwindCursor<LocalAddressSpace, REGISTER_KIND>) <=
+ sizeof(unw_cursor_t), "Unwind cursor does not fit in unw_cursor_t");
+ // Use "placement new" to allocate UnwindCursor in the cursor buffer.
+ new ((void *)cursor) UnwindCursor<LocalAddressSpace, REGISTER_KIND>(
+ context, LocalAddressSpace::sThisAddressSpace);
+#undef REGISTER_KIND
AbstractUnwindCursor *co = (AbstractUnwindCursor *)cursor;
co->setInfoBasedOnIPRegister();
Index: src/UnwindCursor.hpp
===================================================================
--- src/UnwindCursor.hpp
+++ src/UnwindCursor.hpp
@@ -481,30 +481,36 @@
return stepWithCompactEncoding(dummy);
}
+#if defined(__x86_64__)
int stepWithCompactEncoding(Registers_x86_64 &) {
return CompactUnwinder_x86_64<A>::stepWithCompactEncoding(
_info.format, _info.start_ip, _addressSpace, _registers);
}
+#elif defined(__i386__)
int stepWithCompactEncoding(Registers_x86 &) {
return CompactUnwinder_x86<A>::stepWithCompactEncoding(
_info.format, (uint32_t)_info.start_ip, _addressSpace, _registers);
}
+#elif defined(__ppc__)
int stepWithCompactEncoding(Registers_ppc &) {
return UNW_EINVAL;
}
+#elif defined(__arm64__) || defined(__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(__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)
@@ -514,6 +520,7 @@
return false;
}
+#elif defined(__i386__)
bool compactSaysUseDwarf(Registers_x86 &, uint32_t *offset) const {
if ((_info.format & UNWIND_X86_MODE_MASK) == UNWIND_X86_MODE_DWARF) {
if (offset)
@@ -523,45 +530,54 @@
return false;
}
+#elif defined(__ppc__)
bool compactSaysUseDwarf(Registers_ppc &, uint32_t *) const {
return true;
}
+#elif defined(__arm64__) || defined(__aarch64__)
bool compactSaysUseDwarf(Registers_arm64 &, uint32_t *offset) const {
if ((_info.format & UNWIND_ARM64_MODE_MASK) == UNWIND_ARM64_MODE_DWARF) {
if (offset)
*offset = (_info.format & UNWIND_ARM64_DWARF_SECTION_OFFSET);
return true;
}
return false;
}
+#endif
#endif // _LIBUNWIND_SUPPORT_COMPACT_UNWIND
#if _LIBUNWIND_SUPPORT_DWARF_UNWIND
compact_unwind_encoding_t dwarfEncoding() const {
R dummy;
return dwarfEncoding(dummy);
}
+#if defined(__x86_64__)
compact_unwind_encoding_t dwarfEncoding(Registers_x86_64 &) const {
return UNWIND_X86_64_MODE_DWARF;
}
+#elif defined(__i386__)
compact_unwind_encoding_t dwarfEncoding(Registers_x86 &) const {
return UNWIND_X86_MODE_DWARF;
}
+#elif defined(__ppc__)
compact_unwind_encoding_t dwarfEncoding(Registers_ppc &) const {
return 0;
}
+#elif defined(__arm64__) || defined(__aarch64__)
compact_unwind_encoding_t dwarfEncoding(Registers_arm64 &) const {
return UNWIND_ARM64_MODE_DWARF;
}
+#elif defined (__or1k__)
compact_unwind_encoding_t dwarfEncoding(Registers_or1k &) const {
return 0;
}
+#endif
#endif // _LIBUNWIND_SUPPORT_DWARF_UNWIND
Index: src/Registers.hpp
===================================================================
--- src/Registers.hpp
+++ src/Registers.hpp
@@ -24,7 +24,7 @@
// For emulating 128-bit registers
struct v128 { uint32_t vec[4]; };
-
+#if defined(__i386__)
/// Registers_x86 holds the register state of a thread in a 32-bit intel
/// process.
class _LIBUNWIND_HIDDEN Registers_x86 {
@@ -212,7 +212,7 @@
_LIBUNWIND_ABORT("no x86 vector registers");
}
-
+#elif defined(__x86_64__)
/// Registers_x86_64 holds the register state of a thread in a 64-bit intel
/// process.
class _LIBUNWIND_HIDDEN Registers_x86_64 {
@@ -460,7 +460,7 @@
_LIBUNWIND_ABORT("no x86_64 vector registers");
}
-
+#elif defined(__ppc__)
/// Registers_ppc holds the register state of a thread in a 32-bit PowerPC
/// process.
class _LIBUNWIND_HIDDEN Registers_ppc {
@@ -1024,7 +1024,7 @@
}
-
+#elif defined(__arm64__) || defined(__aarch64__)
/// Registers_arm64 holds the register state of a thread in a 64-bit arm
/// process.
class _LIBUNWIND_HIDDEN Registers_arm64 {
@@ -1290,6 +1290,7 @@
_LIBUNWIND_ABORT("no arm64 vector register support yet");
}
+#elif _LIBUNWIND_ARM_EHABI
/// Registers_arm holds the register state of a thread in a 32-bit arm
/// process.
///
@@ -1395,7 +1396,7 @@
_saved_vfp_d16_d31(false),
_saved_iwmmx(false),
_saved_iwmmx_control(false) {
- static_assert(sizeof(Registers_arm) < sizeof(unw_context_t),
+ static_assert(sizeof(Registers_arm) <= sizeof(unw_context_t),
"arm registers do not fit into unw_context_t");
// See unw_getcontext() note about data.
memcpy(&_registers, registers, sizeof(_registers));
@@ -1711,6 +1712,8 @@
inline void Registers_arm::setVectorRegister(int, v128) {
_LIBUNWIND_ABORT("ARM vector support not implemented");
}
+
+#elif defined(__or1k__)
/// Registers_or1k holds the register state of a thread in an OpenRISC1000
/// process.
class _LIBUNWIND_HIDDEN Registers_or1k {
@@ -1893,6 +1896,9 @@
}
}
+#else
+#error "Architecture not supported."
+#endif
} // namespace libunwind
#endif // __REGISTERS_HPP__
Index: src/CompactUnwinder.hpp
===================================================================
--- src/CompactUnwinder.hpp
+++ src/CompactUnwinder.hpp
@@ -27,6 +27,7 @@
namespace libunwind {
+#if defined(__i386__)
/// CompactUnwinder_x86 uses a compact unwind info to virtually "step" (aka
/// unwind) by modifying a Registers_x86 register set
template <typename A>
@@ -256,7 +257,7 @@
registers.setSP((uint32_t)returnAddressLocation + 4);
}
-
+#elif defined(__x86_64__)
/// CompactUnwinder_x86_64 uses a compact unwind info to virtually "step" (aka
/// unwind) by modifying a Registers_x86_64 register set
template <typename A>
@@ -486,7 +487,7 @@
}
-
+#elif defined(__arm64__) || defined(__aarch64__)
/// CompactUnwinder_arm64 uses a compact unwind info to virtually "step" (aka
/// unwind) by modifying a Registers_arm64 register set
template <typename A>
@@ -686,6 +687,7 @@
return UNW_STEP_SUCCESS;
}
+#endif
} // namespace libunwind
Index: include/libunwind.h
===================================================================
--- include/libunwind.h
+++ include/libunwind.h
@@ -46,12 +46,25 @@
};
struct unw_context_t {
+#if defined(__arm__) && defined(_LIBUNWIND_IS_BAREMETAL)
+ // For bare-metal arm targets, use just enough space to hold the
+ // virtual register set (Registers_arm). This helps limit unwinder's
+ // stack usage.
+ uint64_t data[60];
+#else
uint64_t data[128];
+#endif
};
typedef struct unw_context_t unw_context_t;
struct unw_cursor_t {
+#if defined(__arm__) && defined(_LIBUNWIND_IS_BAREMETAL)
+ // As before (unw_context_t), use just enough space to hold the
+ // unwind cursor.
+ uint64_t data[68];
+#else
uint64_t data[140];
+#endif
};
typedef struct unw_cursor_t unw_cursor_t;
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