Triple: Fix handling of macos with unexpected target arches (#75469)

Some tools with a specified target arch, but no full triple default to
the host triple. On macos hosts, this would then force using macho on
targets that didn't expect it, resulting in assertions.

We should also probably emit explicit errors if the object format is
specified on targets which don't handle it.

Author: arsenm

llvm/lib/TargetParser/Triple.cpp

@@ -819,8 +819,6 @@ static Triple::SubArchType parseSubArch(StringRef SubArchName) {
 }
 
 static Triple::ObjectFormatType getDefaultFormat(const Triple &T) {
-  if (T.isOSDarwin())
-    return Triple::MachO;
   switch (T.getArch()) {
   case Triple::UnknownArch:
   case Triple::aarch64:
@@ -829,12 +827,13 @@ static Triple::ObjectFormatType getDefaultFormat(const Triple &T) {
   case Triple::thumb:
   case Triple::x86:
   case Triple::x86_64:
-    if (T.isOSWindows())
+    switch (T.getOS()) {
+    case Triple::Win32:
+    case Triple::UEFI:
       return Triple::COFF;
-    else if (T.isUEFI())
-      return Triple::COFF;
-    return Triple::ELF;
-
+    default:
+      return T.isOSDarwin() ? Triple::MachO : Triple::ELF;
+    }
   case Triple::aarch64_be:
   case Triple::amdgcn:
   case Triple::amdil64:
@@ -887,6 +886,8 @@ static Triple::ObjectFormatType getDefaultFormat(const Triple &T) {
   case Triple::ppc:
     if (T.isOSAIX())
       return Triple::XCOFF;
+    if (T.isOSDarwin())
+      return Triple::MachO;
     return Triple::ELF;
 
   case Triple::systemz:

llvm/unittests/TargetParser/TripleTest.cpp

@@ -2037,6 +2037,13 @@ TEST(TripleTest, FileFormat) {
   T.setObjectFormat(Triple::SPIRV);
   EXPECT_EQ(Triple::SPIRV, T.getObjectFormat());
   EXPECT_EQ("spirv", Triple::getObjectFormatTypeName(T.getObjectFormat()));
+
+  EXPECT_EQ(Triple::ELF, Triple("amdgcn-apple-macosx").getObjectFormat());
+  EXPECT_EQ(Triple::ELF, Triple("r600-apple-macosx").getObjectFormat());
+  EXPECT_EQ(Triple::SPIRV, Triple("spirv-apple-macosx").getObjectFormat());
+  EXPECT_EQ(Triple::SPIRV, Triple("spirv32-apple-macosx").getObjectFormat());
+  EXPECT_EQ(Triple::SPIRV, Triple("spirv64-apple-macosx").getObjectFormat());
+  EXPECT_EQ(Triple::DXContainer, Triple("dxil-apple-macosx").getObjectFormat());
 }
 
 TEST(TripleTest, NormalizeWindows) {