ReaderWriter: teach PE/COFF backend about ARM NT

This teaches lld about the ARM NT object types.  Add a trivial test to ensure
that it can handle ARM NT object file inputs.  It is still unable to perform the
necessary relocations for ARM NT, but this allows the linker to at least read
the objects.

llvm-svn: 225052

lld/lib/ReaderWriter/PECOFF/ReaderCOFF.cpp

@@ -932,6 +932,9 @@ std::error_code FileCOFF::getReferenceArch(Reference::KindArch &result) {
   case llvm::COFF::IMAGE_FILE_MACHINE_AMD64:
     result = Reference::KindArch::x86_64;
     return std::error_code();
+  case llvm::COFF::IMAGE_FILE_MACHINE_ARMNT:
+    result = Reference::KindArch::ARM;
+    return std::error_code();
   case llvm::COFF::IMAGE_FILE_MACHINE_UNKNOWN:
     result = Reference::KindArch::all;
     return std::error_code();

lld/lib/ReaderWriter/PECOFF/WriterPECOFF.cpp

@@ -697,6 +697,9 @@ void AtomChunk::addBaseRelocations(std::vector<uint64_t> &relocSites) const {
   case llvm::COFF::IMAGE_FILE_MACHINE_AMD64:
     relType = llvm::COFF::IMAGE_REL_AMD64_ADDR64;
     break;
+  case llvm::COFF::IMAGE_FILE_MACHINE_ARMNT:
+    relType = llvm::COFF::IMAGE_REL_ARM_ADDR32;
+    break;
   }
 
   for (const auto *layout : _atomLayouts) {

lld/test/pecoff/Inputs/armnt-obj.s

@@ -0,0 +1,12 @@
+
+	.syntax unified
+	.thumb
+	.text
+
+	.def main
+		.scl 2
+		.type 32
+	.endef
+main:
+	bx lr
+

lld/test/pecoff/Inputs/armnt-obj.yaml

@@ -0,0 +1,29 @@
+---
+header:
+  Machine:         IMAGE_FILE_MACHINE_ARMNT
+  Characteristics: [  ]
+sections:
+  - Name:            .text
+    Characteristics: [ IMAGE_SCN_CNT_CODE, IMAGE_SCN_MEM_PURGEABLE, IMAGE_SCN_MEM_16BIT, IMAGE_SCN_MEM_EXECUTE, IMAGE_SCN_MEM_READ ]
+    Alignment:       4
+    SectionData:     '7047'
+symbols:
+  - Name:            .text
+    Value:           0
+    SectionNumber:   1
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_NULL
+    StorageClass:    IMAGE_SYM_CLASS_STATIC
+    SectionDefinition:
+      Length:          2
+      NumberOfRelocations: 0
+      NumberOfLinenumbers: 0
+      CheckSum:        0
+      Number:          1
+  - Name:            main
+    Value:           0
+    SectionNumber:   1
+    SimpleType:      IMAGE_SYM_TYPE_NULL
+    ComplexType:     IMAGE_SYM_DTYPE_FUNCTION
+    StorageClass:    IMAGE_SYM_CLASS_EXTERNAL
+...

lld/test/pecoff/armnt.test

@@ -0,0 +1,6 @@
+# RUN: yaml2obj -format coff -o %t.obj %p/Inputs/armnt-obj.yaml
+# RUN: lld -flavor link /out:%t.dll /subsystem:console /entry:main %t.obj
+# RUN: llvm-readobj -sections %t.dll | FileCheck %s
+
+CHECK: Format: COFF-ARM
+