[macho] save the SDK version stored in module metadata into the version min and

build version load commands in the object file

This commit introduces a new metadata node called "SDK Version". It will be set
by the frontend to mark the platform SDK (macOS/iOS/etc) version which was used
during that particular compilation.
This node is used when machine code is emitted, by either saving the SDK version
into the appropriate macho load command (version min/build version), or by
emitting the assembly for these load commands with the SDK version specified as
well.
The assembly for both load commands is extended by allowing it to contain the
sdk_version X, Y [, Z] trailing directive to represent the SDK version
respectively.

rdar://45774000

Differential Revision: https://reviews.llvm.org/D55612

llvm-svn: 349119

1 files changed, 16 insertions, 7 deletions

diff --git a/llvm/lib/MC/MachObjectWriter.cpp b/llvm/lib/MC/MachObjectWriter.cpp
index c2e8dc1ef65..2fa65658ccf 100644
--- a/llvm/lib/MC/MachObjectWriter.cpp
+++ b/llvm/lib/MC/MachObjectWriter.cpp
@@ -846,18 +846,27 @@ uint64_t MachObjectWriter::writeObject(MCAssembler &Asm,
 
   // Write out the deployment target information, if it's available.
   if (VersionInfo.Major != 0) {
-    assert(VersionInfo.Update < 256 && "unencodable update target version");
-    assert(VersionInfo.Minor < 256 && "unencodable minor target version");
-    assert(VersionInfo.Major < 65536 && "unencodable major target version");
-    uint32_t EncodedVersion = VersionInfo.Update | (VersionInfo.Minor << 8) |
-      (VersionInfo.Major << 16);
+    auto EncodeVersion = [](VersionTuple V) -> uint32_t {
+      assert(!V.empty() && "empty version");
+      unsigned Update = V.getSubminor() ? *V.getSubminor() : 0;
+      unsigned Minor = V.getMinor() ? *V.getMinor() : 0;
+      assert(Update < 256 && "unencodable update target version");
+      assert(Minor < 256 && "unencodable minor target version");
+      assert(V.getMajor() < 65536 && "unencodable major target version");
+      return Update | (Minor << 8) | (V.getMajor() << 16);
+    };
+    uint32_t EncodedVersion = EncodeVersion(
+        VersionTuple(VersionInfo.Major, VersionInfo.Minor, VersionInfo.Update));
+    uint32_t SDKVersion = !VersionInfo.SDKVersion.empty()
+                              ? EncodeVersion(VersionInfo.SDKVersion)
+                              : 0;
     if (VersionInfo.EmitBuildVersion) {
       // FIXME: Currently empty tools. Add clang version in the future.
       W.write<uint32_t>(MachO::LC_BUILD_VERSION);
       W.write<uint32_t>(sizeof(MachO::build_version_command));
       W.write<uint32_t>(VersionInfo.TypeOrPlatform.Platform);
       W.write<uint32_t>(EncodedVersion);
-      W.write<uint32_t>(0);         // SDK version.
+      W.write<uint32_t>(SDKVersion);
       W.write<uint32_t>(0);         // Empty tools list.
     } else {
       MachO::LoadCommandType LCType
@@ -865,7 +874,7 @@ uint64_t MachObjectWriter::writeObject(MCAssembler &Asm,
       W.write<uint32_t>(LCType);
       W.write<uint32_t>(sizeof(MachO::version_min_command));
       W.write<uint32_t>(EncodedVersion);
-      W.write<uint32_t>(0);         // reserved.
+      W.write<uint32_t>(SDKVersion);
     }
   }