[PATCH] Split Alignment out of the Section Characteristics

[Rafael Ávila de Espíndola]

Hi Bigcheese,

I have converted obj2yaml to use yamio. One problem I found comparing a yaml -> .o -> yaml roundtrip is the section alignment. Unlike the rest of the Characteristics field, it is just a plain byte, not a series of flags. This causes a IMAGE_SCN_ALIGN_16BYTES  to be printed as

IMAGE_SCN_ALIGN_16BYTES,  IMAGE_SCN_ALIGN_8BYTES, IMAGE_SCN_ALIGN_1BYTES

Since the yaml representation has a more semantic view of the file, I think the best solution is to just add a distinct field for alignment in the yaml representation.

http://llvm-reviews.chandlerc.com/D734

Files:
  test/Object/Inputs/COFF/i386.yaml
  test/Object/Inputs/COFF/x86-64.yaml
  tools/yaml2obj/yaml2obj.cpp

Index: test/Object/Inputs/COFF/i386.yaml
===================================================================
--- test/Object/Inputs/COFF/i386.yaml
+++ test/Object/Inputs/COFF/i386.yaml
@@ -5,7 +5,8 @@
 sections:
   - !Section
     Name: .text
-    Characteristics: [IMAGE_SCN_CNT_CODE, IMAGE_SCN_ALIGN_16BYTES, IMAGE_SCN_MEM_EXECUTE, IMAGE_SCN_MEM_READ, ] # 0x60500020
+    Alignment: 16
+    Characteristics: [IMAGE_SCN_CNT_CODE, IMAGE_SCN_MEM_EXECUTE, IMAGE_SCN_MEM_READ, ] # 0x60500020
     SectionData:  !hex "83EC0CC744240800000000C7042400000000E800000000E8000000008B44240883C40CC3" # |....D$.......$...............D$.....|
 
     Relocations:
@@ -26,7 +27,8 @@
 
   - !Section
     Name: .data
-    Characteristics: [IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_ALIGN_1BYTES, IMAGE_SCN_MEM_READ, IMAGE_SCN_MEM_WRITE, ] # 0xc0100040
+    Alignment: 1
+    Characteristics: [IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_READ, IMAGE_SCN_MEM_WRITE, ] # 0xc0100040
     SectionData:  !hex "48656C6C6F20576F726C642100" # |Hello World!.|
 
 symbols:
Index: test/Object/Inputs/COFF/x86-64.yaml
===================================================================
--- test/Object/Inputs/COFF/x86-64.yaml
+++ test/Object/Inputs/COFF/x86-64.yaml
@@ -4,7 +4,8 @@
 sections:
   - !Section
     Name: .text
-    Characteristics: [IMAGE_SCN_CNT_CODE, IMAGE_SCN_ALIGN_16BYTES, IMAGE_SCN_MEM_EXECUTE, IMAGE_SCN_MEM_READ, ] # 0x60500020
+    Alignment: 16
+    Characteristics: [IMAGE_SCN_CNT_CODE, IMAGE_SCN_MEM_EXECUTE, IMAGE_SCN_MEM_READ, ] # 0x60500020
     SectionData:  !hex "4883EC28C744242400000000488D0D00000000E800000000E8000000008B4424244883C428C3" # |H..(.D$$....H.................D$$H..(.|
 
     Relocations:
@@ -25,7 +26,8 @@
 
   - !Section
     Name: .data
-    Characteristics: [IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_ALIGN_1BYTES, IMAGE_SCN_MEM_READ, IMAGE_SCN_MEM_WRITE, ] # 0xc0100040
+    Alignment: 1
+    Characteristics: [IMAGE_SCN_CNT_INITIALIZED_DATA, IMAGE_SCN_MEM_READ, IMAGE_SCN_MEM_WRITE, ] # 0xc0100040
     SectionData:  !hex "48656C6C6F20576F726C642100" # |Hello World!.|
 
 symbols:
Index: tools/yaml2obj/yaml2obj.cpp
===================================================================
--- tools/yaml2obj/yaml2obj.cpp
+++ tools/yaml2obj/yaml2obj.cpp
@@ -42,6 +42,7 @@
 namespace COFFYAML {
   struct Section {
     COFF::section Header;
+    unsigned Alignment;
     StringRef SectionData;
     std::vector<COFF::relocation> Relocations;
     StringRef Name;
@@ -102,6 +103,8 @@
         Sec.Header.Name[0] = '/';
         std::copy(str.begin(), str.end(), Sec.Header.Name + 1);
       }
+
+      Sec.Header.Characteristics |= (Log2_32(Sec.Alignment) + 1) << 20;
     }
     return true;
   }
@@ -358,20 +361,6 @@
     BCase(IMAGE_SCN_MEM_16BIT);
     BCase(IMAGE_SCN_MEM_LOCKED);
     BCase(IMAGE_SCN_MEM_PRELOAD);
-    BCase(IMAGE_SCN_ALIGN_1BYTES);
-    BCase(IMAGE_SCN_ALIGN_2BYTES);
-    BCase(IMAGE_SCN_ALIGN_4BYTES);
-    BCase(IMAGE_SCN_ALIGN_8BYTES);
-    BCase(IMAGE_SCN_ALIGN_16BYTES);
-    BCase(IMAGE_SCN_ALIGN_32BYTES);
-    BCase(IMAGE_SCN_ALIGN_64BYTES);
-    BCase(IMAGE_SCN_ALIGN_128BYTES);
-    BCase(IMAGE_SCN_ALIGN_256BYTES);
-    BCase(IMAGE_SCN_ALIGN_512BYTES);
-    BCase(IMAGE_SCN_ALIGN_1024BYTES);
-    BCase(IMAGE_SCN_ALIGN_2048BYTES);
-    BCase(IMAGE_SCN_ALIGN_4096BYTES);
-    BCase(IMAGE_SCN_ALIGN_8192BYTES);
     BCase(IMAGE_SCN_LNK_NRELOC_OVFL);
     BCase(IMAGE_SCN_MEM_DISCARDABLE);
     BCase(IMAGE_SCN_MEM_NOT_CACHED);
@@ -641,6 +630,7 @@
     IO.mapRequired("SectionData", Sec.SectionData);
     IO.mapRequired("Characteristics", NC->Characteristics);
     IO.mapRequired("Name", Sec.Name);
+    IO.mapOptional("Alignment", Sec.Alignment);
   }
 };
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