Set TARGET_OS_* from GN, falling back to HOST_OS_*.

runtime/vm/snapshot.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/snapshot.h"
 
 #include "platform/assert.h"
 #include "vm/bootstrap.h"
 #include "vm/class_finalizer.h"
 #include "vm/dart.h"
@@ skipping 878 matching lines @@
       ASSERT(Utils::IsAligned(beginning, sizeof(uword)));
       ASSERT(Utils::IsAligned(entry, sizeof(uword)));
       ASSERT(Utils::IsAligned(end, sizeof(uword)));
 
       WriteByteSequence(entry, end);
     }
   }
 
   FrameUnwindEpilogue();
 
-#if defined(HOST_OS_LINUX)
+#if defined(TARGET_OS_LINUX) || defined(TARGET_OS_ANDROID) ||                  \
+    defined(TARGET_OS_FUCHSIA)
   assembly_stream_.Print(".section .rodata\n");
-#elif defined(HOST_OS_MACOS)
+#elif defined(TARGET_OS_MACOS) || defined(TARGET_OS_MACOS_IOS)
   assembly_stream_.Print(".const\n");
 #else
-  // Unsupported platform.
-  UNREACHABLE();
+  UNIMPLEMENTED();
 #endif
 
   const char* data_symbol =
       vm ? "_kDartVmSnapshotData" : "_kDartIsolateSnapshotData";
   assembly_stream_.Print(".globl %s\n", data_symbol);
   assembly_stream_.Print(".balign %" Pd ", 0\n",
                          OS::kMaxPreferredCodeAlignment);
   assembly_stream_.Print("%s:\n", data_symbol);
   uword buffer = reinterpret_cast<uword>(clustered_stream->buffer());
   intptr_t length = clustered_stream->bytes_written();
@@ skipping 31 matching lines @@
   // Should be ".cfi_value_offset sp, 16", but requires gcc newer than late
   // 2016 and not supported by Android's libunwind.
   // DW_CFA_expression          0x10
   // uleb128 register (x31)       31
   // uleb128 size of operation     2
   // DW_OP_plus_uconst          0x23
   // uleb128 addend               16
   assembly_stream_.Print(".cfi_escape 0x10, 31, 2, 0x23, 16\n");
 
 #elif defined(TARGET_ARCH_ARM)
-#if defined(TARGET_ABI_EABI)
+#if defined(TARGET_OS_MACOS) || defined(TARGET_OS_MACOS_IOS)
+  COMPILE_ASSERT(FP == R7);
+  assembly_stream_.Print(".cfi_def_cfa r7, 0\n");   // CFA is fp+j0
+  assembly_stream_.Print(".cfi_offset r7, 0\n");    // saved fp is *(CFA+0)
+#else
   COMPILE_ASSERT(FP == R11);
   assembly_stream_.Print(".cfi_def_cfa r11, 0\n");  // CFA is fp+0
   assembly_stream_.Print(".cfi_offset r11, 0\n");   // saved fp is *(CFA+0)
-#elif defined(TARGET_ABI_IOS)
-  COMPILE_ASSERT(FP == R7);
-  assembly_stream_.Print(".cfi_def_cfa r7, 0\n");  // CFA is fp+0
-  assembly_stream_.Print(".cfi_offset r7, 0\n");   // saved fp is *(CFA+0)
 #endif
   assembly_stream_.Print(".cfi_offset lr, 4\n");    // saved pc is *(CFA+4)
   // saved sp is CFA+8
   // Should be ".cfi_value_offset sp, 8", but requires gcc newer than late
   // 2016 and not supported by Android's libunwind.
   // DW_CFA_expression          0x10
   // uleb128 register (sp)        13
   // uleb128 size of operation     2
   // DW_OP_plus_uconst          0x23
   // uleb128 addend                8
   assembly_stream_.Print(".cfi_escape 0x10, 13, 2, 0x23, 8\n");
 
 // libunwind on ARM may use .ARM.exidx instead of .debug_frame
-#if defined(TARGET_ABI_EABI)
+#if defined(TARGET_OS_MACOS) || defined(TARGET_OS_MACOS_IOS)
+  COMPILE_ASSERT(FP == R7);
+  assembly_stream_.Print(".fnstart\n");
+  assembly_stream_.Print(".save {r7, lr}\n");
+  assembly_stream_.Print(".setfp r7, sp, #0\n");
+#else
   COMPILE_ASSERT(FP == R11);
   assembly_stream_.Print(".fnstart\n");
   assembly_stream_.Print(".save {r11, lr}\n");
   assembly_stream_.Print(".setfp r11, sp, #0\n");
-#elif defined(TARGET_ABI_IOS)
-  COMPILE_ASSERT(FP == R7);
-  assembly_stream_.Print(".fnstart\n");
-  assembly_stream_.Print(".save {r7, lr}\n");
-  assembly_stream_.Print(".setfp r7, sp, #0\n");
 #endif
 
 #elif defined(TARGET_ARCH_MIPS)
   COMPILE_ASSERT(FP == R30);
   COMPILE_ASSERT(RA == R31);
   assembly_stream_.Print(".cfi_def_cfa r30, 0\n");  // CFA is fp+0
   assembly_stream_.Print(".cfi_offset r30, 0\n");   // saved fp is *(CFA+0)
   assembly_stream_.Print(".cfi_offset r31, 4\n");   // saved pc is *(CFA+4)
   // saved sp is CFA+16
   // Should be ".cfi_value_offset sp, 8", but requires gcc newer than late
@@ skipping 1048 matching lines @@
       *buffer_len_ = BytesWritten();
     }
   } else {
     FreeBuffer();
     ThrowException(exception_type(), exception_msg());
   }
 }
 
 
 }  // namespace dart