[libunwind] Fix SEH unwinding on ARM

[mstorsjo]

Summary

Check __SEH__ when checking if ARM EHABI should be impliied.

Fix a warning by using the right format specifier (PRIxPTR instead
of PRIx64), and add a double->float cast in a codepath that hasn't
been built so far.

This is enough to make SEH unwinding of itanium ABI exceptions on
ARM mostly work - one specific issue is fixed in a separate follow-up
patch.

libunwind/include/__libunwind_config.h

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef ____LIBUNWIND_CONFIG_H__
 #define ____LIBUNWIND_CONFIG_H__
 
 #define _LIBUNWIND_VERSION 15000
 
 #if defined(__arm__) && !defined(__USING_SJLJ_EXCEPTIONS__) && \
-    !defined(__ARM_DWARF_EH__)
+    !defined(__ARM_DWARF_EH__) && !defined(__SEH__)
 #define _LIBUNWIND_ARM_EHABI
 #endif
 
 #define _LIBUNWIND_HIGHEST_DWARF_REGISTER_X86       8
 #define _LIBUNWIND_HIGHEST_DWARF_REGISTER_X86_64    32
 #define _LIBUNWIND_HIGHEST_DWARF_REGISTER_PPC       112
 #define _LIBUNWIND_HIGHEST_DWARF_REGISTER_PPC64     116
 #define _LIBUNWIND_HIGHEST_DWARF_REGISTER_ARM64     95

libunwind/include/libunwind.h

struct unw_cursor_t {
   uint64_t data[_LIBUNWIND_CURSOR_SIZE];
 } LIBUNWIND_CURSOR_ALIGNMENT_ATTR;
 typedef struct unw_cursor_t unw_cursor_t;
 
 typedef struct unw_addr_space *unw_addr_space_t;
 
 typedef int unw_regnum_t;
 typedef uintptr_t unw_word_t;
-#if defined(__arm__) && !defined(__ARM_DWARF_EH__)
+#if defined(__arm__) && !defined(__ARM_DWARF_EH__) && !defined(__SEH__)
 typedef uint64_t unw_fpreg_t;
 #else
 typedef double unw_fpreg_t;
 #endif
 
 struct unw_proc_info_t {
   unw_word_t  start_ip;         /* start address of function */
   unw_word_t  end_ip;           /* address after end of function */

libunwind/src/Unwind-seh.cpp

if (_LIBUNWIND_TRACING_UNWINDING) {
       char functionBuf[512];
       const char *functionName = functionBuf;
       unw_word_t offset;
       if ((__unw_get_proc_name(&cursor2, functionBuf, sizeof(functionBuf),
                                &offset) != UNW_ESUCCESS) ||
           (frameInfo.start_ip + offset > frameInfo.end_ip))
         functionName = ".anonymous.";
       _LIBUNWIND_TRACE_UNWINDING(
-          "unwind_phase2_forced(ex_ojb=%p): start_ip=0x%" PRIx64
-          ", func=%s, lsda=0x%" PRIx64 ", personality=0x%" PRIx64,
+          "unwind_phase2_forced(ex_ojb=%p): start_ip=0x%" PRIxPTR
+          ", func=%s, lsda=0x%" PRIxPTR ", personality=0x%" PRIxPTR,
           (void *)exception_object, frameInfo.start_ip, functionName,
           frameInfo.lsda, frameInfo.handler);
     }
 #endif
 
     // Call stop function at each frame.
     _Unwind_Action action =
         (_Unwind_Action)(_UA_FORCE_UNWIND | _UA_CLEANUP_PHASE);

libunwind/src/UnwindCursor.hpp

 template <typename A, typename R>
 void UnwindCursor<A, R>::setFloatReg(int regNum, unw_fpreg_t value) {
 #if defined(_LIBUNWIND_TARGET_ARM)
   if (regNum >= UNW_ARM_S0 && regNum <= UNW_ARM_S31) {
     union {
       uint32_t w;
       float f;
     } d;
-    d.f = value;
+    d.f = (float)value;
     _msContext.S[regNum - UNW_ARM_S0] = d.w;
   }
   if (regNum >= UNW_ARM_D0 && regNum <= UNW_ARM_D31) {
     union {
       uint64_t w;
       double d;
     } d;
     d.d = value;