[ARM] Emit the missing Tag_ABI_enum_size build attribute values

[labrinea]

Summary

The ABI for the ARM architecture describes four build attribute values for the size of enumeration types. Currently, LLVM cannot emit the value 0 (use of enums is prohibited) and 3 (every enumeration visible across an ABI-complying interface contains a value needing 32 bits to encode). This patch adds support for emitting the missing build attribute values.

This patch depends on Add Driver support for emitting the missing Tag_ABI_enum_size build attribute values.

[jmolloy]

Other than my inline comment this looks good!

lib/Target/ARM/ARMAsmPrinter.cpp

924

My feeling here is that we need to maintain support for the min_enum_size metadata for a while. Our bitcode policy is that it should auto-upgrade for 2 releases.

I'm aware that metadata is normally excluded from this, but this particular metadata, if omitted, will cause link failures. So I think a fallback is needed.

[labrinea]

Added the fallback logic for backwards compatibility.

[labrinea]

Abandoning this on the base that Add Driver support for emitting the missing Tag_ABI_enum_size build attribute values has been abandoned. Apologies and thank you for reviewing this.

lib/Target/ARM/ARMAsmPrinter.cpp

if (const Module *SourceModule = MMI->getModule()) {
       if (auto WCharWidthValue = mdconst::extract_or_null<ConstantInt>(
               SourceModule->getModuleFlag("wchar_size"))) {
         int WCharWidth = WCharWidthValue->getZExtValue();
         assert((WCharWidth == 2 || WCharWidth == 4) &&
                "wchar_t width must be 2 or 4 bytes");
         ATS.emitAttribute(ARMBuildAttrs::ABI_PCS_wchar_t, WCharWidth);
       }
 
-      // ABI_enum_size to indicate enum width
-      // FIXME: There is no way to emit value 0 (enums prohibited) or value 3
-      //        (all enums contain a value needing 32 bits to encode).
-      if (auto EnumWidthValue = mdconst::extract_or_null<ConstantInt>(
+      // Generate the correct Tag_ABI_enum_size build attribute.
+      if (auto BuildAttrValue = mdconst::extract_or_null<ConstantInt>(
+              SourceModule->getModuleFlag("enumsize_buildattr"))) {
+        int EnumSizeBuildAttr = BuildAttrValue->getZExtValue();
+        assert((EnumSizeBuildAttr == ARMBuildAttrs::EnumProhibited ||
+                EnumSizeBuildAttr == ARMBuildAttrs::EnumSmallest ||
+                EnumSizeBuildAttr == ARMBuildAttrs::Enum32Bit ||
+                EnumSizeBuildAttr == ARMBuildAttrs::Enum32BitABI) &&
+               "Unsupported build attribute");
+        ATS.emitAttribute(ARMBuildAttrs::ABI_enum_size, EnumSizeBuildAttr);
+      // We keep this for backwards compatibility with older versions of Clang.
+      } else if (auto EnumWidthValue = mdconst::extract_or_null<ConstantInt>(
                      SourceModule->getModuleFlag("min_enum_size"))) {
         int EnumWidth = EnumWidthValue->getZExtValue();
         assert((EnumWidth == 1 || EnumWidth == 4) &&
                "Minimum enum width must be 1 or 4 bytes");
         int EnumBuildAttr = EnumWidth == 1 ? 1 : 2;
         ATS.emitAttribute(ARMBuildAttrs::ABI_enum_size, EnumBuildAttr);
       }
     }
   }
 
   // We currently do not support using R9 as the TLS pointer.
   if (STI.isRWPI())
     ATS.emitAttribute(ARMBuildAttrs::ABI_PCS_R9_use,
                       ARMBuildAttrs::R9IsSB);

test/CodeGen/ARM/2016-08-24-ARM-LDST-dbginfo-bug.ll

 !llvm.module.flags = !{!3, !4, !5, !6}
 
 !0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 4.0.0 ", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
 !1 = !DIFile(filename: "test.c", directory: "/a/b/c")
 !2 = !{}
 !3 = !{i32 2, !"Dwarf Version", i32 4}
 !4 = !{i32 2, !"Debug Info Version", i32 3}
 !5 = !{i32 1, !"wchar_size", i32 4}
-!6 = !{i32 1, !"min_enum_size", i32 4}
+!6 = !{i32 1, !"enumsize_buildattr", i32 2}
 !7 = !{!"clang version 4.0.0 "}
 !8 = distinct !DISubprogram(name: "s_idx", scope: !1, file: !1, line: 6, type: !9, isLocal: false, isDefinition: true, scopeLine: 7, flags: DIFlagPrototyped, isOptimized: true, unit: !0, variables: !16)
 !9 = !DISubroutineType(types: !10)
 !10 = !{!11, !11}
 !11 = !DIDerivedType(tag: DW_TAG_typedef, name: "ezxml_t", file: !1, line: 1, baseType: !12)
 !12 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !13, size: 32, align: 32)
 !13 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "s", file: !1, line: 2, size: 32, align: 32, elements: !14)
 !14 = !{!15}
 !15 = !DIDerivedType(tag: DW_TAG_member, name: "next", scope: !13, file: !1, line: 3, baseType: !11, size: 32, align: 32)
 !16 = !{!17}
 !17 = !DILocalVariable(name: "xl", arg: 1, scope: !8, file: !1, line: 6, type: !11)
 !18 = !DIExpression()
 !19 = !DILocation(line: 6, column: 27, scope: !8)
 !20 = !DILocation(line: 8, column: 5, scope: !8)

test/CodeGen/ARM/arm-shrink-wrapping-linux.ll

 if.end29:                                         ; preds = %while.cond2, %while.body, %while.cond.preheader
   %s.addr.3 = phi i8* [ %s, %while.cond.preheader ], [ %add.ptr, %while.body ], [ %s.addr.1.ph, %while.cond2 ]
   ret i8* %s.addr.3
 }
 
 !llvm.module.flags = !{!0, !1}
 
 !0 = !{i32 1, !"wchar_size", i32 4}
-!1 = !{i32 1, !"min_enum_size", i32 4}
+!1 = !{i32 1, !"enumsize_buildattr", i32 2}
 !2 = !{!3, !3, i64 0}
 !3 = !{!"omnipotent char", !4, i64 0}
 !4 = !{!"Simple C/C++ TBAA"}

test/CodeGen/ARM/constantpool-promote-dbg.ll

 !llvm.ident = !{!7}
 
 !0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 3.9.0 (http://llvm.org/git/clang.git 075a2bc2570dfcbb6d6aed6c836e4c62b37afea6)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
 !1 = !DIFile(filename: "/Users/jammol01/Code/test.c", directory: "/Users/jammol01/Code/llvm-git/build")
 !2 = !{}
 !3 = !{i32 2, !"Dwarf Version", i32 4}
 !4 = !{i32 2, !"Debug Info Version", i32 3}
 !5 = !{i32 1, !"wchar_size", i32 4}
-!6 = !{i32 1, !"min_enum_size", i32 4}
+!6 = !{i32 1, !"enumsize_buildattr", i32 2}
 !7 = !{!"clang version 3.9.0 (http://llvm.org/git/clang.git 075a2bc2570dfcbb6d6aed6c836e4c62b37afea6)"}
 !8 = distinct !DISubprogram(name: "fn1", scope: !1, file: !1, line: 1, type: !9, isLocal: false, isDefinition: true, scopeLine: 1, isOptimized: true, unit: !0, variables: !2)
 !9 = !DISubroutineType(types: !10)
 !10 = !{!11}
 !11 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !12, size: 32, align: 32)
 !12 = !DIDerivedType(tag: DW_TAG_const_type, baseType: !13)
 !13 = !DIBasicType(name: "char", size: 8, align: 8, encoding: DW_ATE_unsigned_char)
 !14 = !DILocation(line: 2, column: 5, scope: !8)
 !15 = distinct !DISubprogram(name: "fn2", scope: !1, file: !1, line: 4, type: !9, isLocal: false, isDefinition: true, scopeLine: 4, isOptimized: true, unit: !0, variables: !2)
 !16 = !DILocation(line: 5, column: 5, scope: !15)

test/CodeGen/ARM/constantpool-promote.ll

 attributes #0 = { nounwind "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
 attributes #1 = { "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
 attributes #2 = { nounwind }
 
 !llvm.module.flags = !{!0, !1}
 !llvm.ident = !{!2}
 
 !0 = !{i32 1, !"wchar_size", i32 4}
-!1 = !{i32 1, !"min_enum_size", i32 4}
+!1 = !{i32 1, !"enumsize_buildattr", i32 2}
 !2 = !{!"Apple LLVM version 6.1.0 (clang-602.0.53) (based on LLVM 3.6.0svn)"}

test/CodeGen/ARM/metadata-abi-enums.ll

+; RUN: llc < %s | FileCheck %s
+
+target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-n32-S64"
+target triple = "armv7--none-eabi"
+
+define i32 @f(i64 %z) {
+  ret i32 0
+}
+
+!llvm.module.flags = !{!0}
+
+!0 = !{i32 1, !"enumsize_buildattr", i32 3}
+
+; CHECK: .eabi_attribute 26, 3   @ Tag_ABI_enum_size

test/CodeGen/ARM/metadata-default.ll

 ; RUN: llc < %s -mtriple=armv7-linux-gnueabi | FileCheck %s
 
 target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-n32-S64"
 target triple = "armv7--none-eabi"
 
 define i32 @f(i64 %z) {
   ret i32 0
 }
 
 !llvm.module.flags = !{!0, !1}
 
 !0 = !{i32 1, !"wchar_size", i32 4}
-!1 = !{i32 1, !"min_enum_size", i32 4}
+!1 = !{i32 1, !"enumsize_buildattr", i32 2}
 
 ; CHECK: .eabi_attribute 18, 4   @ Tag_ABI_PCS_wchar_t
 ; CHECK: .eabi_attribute 26, 2   @ Tag_ABI_enum_size

test/CodeGen/ARM/metadata-no-enums.ll

+; RUN: llc < %s | FileCheck %s
+
+target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-n32-S64"
+target triple = "armv7--none-eabi"
+
+define i32 @f(i64 %z) {
+  ret i32 0
+}
+
+!llvm.module.flags = !{!0}
+
+!0 = !{i32 1, !"enumsize_buildattr", i32 0}
+
+; CHECK: .eabi_attribute 26, 0   @ Tag_ABI_enum_size

test/CodeGen/ARM/metadata-short-enums.ll

 ; RUN: llc < %s | FileCheck %s
 
 target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-n32-S64"
 target triple = "armv7--none-eabi"
 
 define i32 @f(i64 %z) {
   ret i32 0
 }
 
 !llvm.module.flags = !{!0, !1}
 
 !0 = !{i32 1, !"wchar_size", i32 4}
-!1 = !{i32 1, !"min_enum_size", i32 1}
+!1 = !{i32 1, !"enumsize_buildattr", i32 1}
 
 ; CHECK: .eabi_attribute 18, 4   @ Tag_ABI_PCS_wchar_t
 ; CHECK: .eabi_attribute 26, 1   @ Tag_ABI_enum_size

test/CodeGen/ARM/metadata-short-wchar.ll

 ; RUN: llc < %s | FileCheck %s
 
 target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-n32-S64"
 target triple = "armv7--none-eabi"
 
 define i32 @f(i64 %z) {
   ret i32 0
 }
 
 !llvm.module.flags = !{!0, !1}
 
 !0 = !{i32 1, !"wchar_size", i32 2}
-!1 = !{i32 1, !"min_enum_size", i32 4}
+!1 = !{i32 1, !"enumsize_buildattr", i32 2}
 
 ; CHECK: .eabi_attribute 18, 2   @ Tag_ABI_PCS_wchar_t
 ; CHECK: .eabi_attribute 26, 2   @ Tag_ABI_enum_size

test/CodeGen/MIR/ARM/sched-it-debug-nodes.mir

--- |
   !17 = !{!18, !19, !20, !21}
   !18 = !DILocalVariable(name: "s", arg: 1, scope: !4, file: !1, line: 9, type: !8)
   !19 = !DILocalVariable(name: "u", arg: 2, scope: !4, file: !1, line: 9, type: !11)
   !20 = !DILocalVariable(name: "b", arg: 3, scope: !4, file: !1, line: 9, type: !12)
   !21 = !DILocalVariable(name: "n", arg: 4, scope: !4, file: !1, line: 9, type: !16)
   !22 = !{i32 2, !"Dwarf Version", i32 4}
   !23 = !{i32 2, !"Debug Info Version", i32 3}
   !24 = !{i32 1, !"wchar_size", i32 4}
-  !25 = !{i32 1, !"min_enum_size", i32 4}
+  !25 = !{i32 1, !"enumsize_buildattr", i32 2}
   !26 = !{!"clang version 3.7.0  (llvm/trunk 237059)"}
   !27 = !DIExpression()
   !28 = !DILocation(line: 9, scope: !4)
   !29 = !DILocation(line: 10, scope: !30)
   !30 = distinct !DILexicalBlock(scope: !4, file: !1, line: 10)
   !31 = !DILocation(line: 10, scope: !4)
   !32 = !DILocation(line: 13, scope: !4)
   !33 = !DILocation(line: 14, scope: !4)

test/DebugInfo/ARM/PR26163.ll

 !16 = !DILocalVariable(name: "lifetime", scope: !11, file: !5, line: 13, type: !17)
 !17 = !DICompositeType(tag: DW_TAG_structure_type, name: "timeval", file: !5, line: 2, size: 128, align: 64, elements: !18)
 !18 = !{!19, !21}
 !19 = !DIDerivedType(tag: DW_TAG_member, name: "tv_sec", scope: !17, file: !5, line: 3, baseType: !20, size: 64, align: 64)
 !20 = !DIBasicType(name: "long long int", size: 64, align: 64, encoding: DW_ATE_signed)
 !21 = !DIDerivedType(tag: DW_TAG_member, name: "tv_usec", scope: !17, file: !5, line: 4, baseType: !8, size: 32, align: 32, offset: 64)
 !22 = !{i32 2, !"Debug Info Version", i32 3}
 !23 = !{i32 1, !"wchar_size", i32 4}
-!24 = !{i32 1, !"min_enum_size", i32 4}
+!24 = !{i32 1, !"enumsize_buildattr", i32 2}
 !25 = !{!"clang version 3.9.0 (https://github.com/llvm-mirror/clang 89dda3855cda574f355e6defa1d77bdae5053994) (llvm/trunk 257891)"}
 !26 = !DIExpression()
 !27 = !DILocation(line: 11, scope: !11, inlinedAt: !28)
 !28 = distinct !DILocation(line: 26, scope: !4)
 !29 = !DILocation(line: 13, scope: !11, inlinedAt: !28)
 !30 = !DIExpression(DW_OP_bit_piece, 0, 64)
 !31 = !DIExpression(DW_OP_bit_piece, 0, 32)
 !32 = !DILocation(line: 18, scope: !11, inlinedAt: !28)
 !33 = !DILocation(line: 27, scope: !4)

test/DebugInfo/ARM/big-endian-dump.ll

 ; RUN: llc -O0 -filetype=obj -mtriple=armeb-none-linux < %s | llvm-dwarfdump - | FileCheck %s
 
 ; CHECK: file format ELF32-arm-big
 
 target datalayout = "E-m:e-p:32:32-i64:64-v128:64:128-n32-S64"
 
 !llvm.dbg.cu = !{!0}
 !llvm.module.flags = !{!3, !4, !5, !6}
 !llvm.ident = !{!7}
 
 !0 = !{i32 786449, !1, i32 12, !"clang version 3.6.0 ", i1 false, !"", i32 0, !2, !2, !2, !2, !2, !"", i32 1} ; [ DW_TAG_compile_unit ] [/a/empty.c] [DW_LANG_C99]
 !1 = !{!"empty.c", !"/a"}
 !2 = !{}
 !3 = !{i32 2, !"Dwarf Version", i32 4}
 !4 = !{i32 2, !"Debug Info Version", i32 1}
 !5 = !{i32 1, !"wchar_size", i32 4}
-!6 = !{i32 1, !"min_enum_size", i32 4}
+!6 = !{i32 1, !"enumsize_buildattr", i32 2}
 !7 = !{!"clang version 3.6.0 "}

test/DebugInfo/ARM/little-endian-dump.ll

 ; RUN: llc -O0 -filetype=obj -mtriple=arm-none-linux < %s | llvm-dwarfdump - | FileCheck %s
 
 ; CHECK: file format ELF32-arm-little
 
 target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-n32-S64"
 
 !llvm.dbg.cu = !{!0}
 !llvm.module.flags = !{!3, !4, !5, !6}
 !llvm.ident = !{!7}
 
 !0 = !{i32 786449, !1, i32 12, !"clang version 3.6.0 ", i1 false, !"", i32 0, !2, !2, !2, !2, !2, !"", i32 1} ; [ DW_TAG_compile_unit ] [/a/empty.c] [DW_LANG_C99]
 !1 = !{!"empty.c", !"/a"}
 !2 = !{}
 !3 = !{i32 2, !"Dwarf Version", i32 4}
 !4 = !{i32 2, !"Debug Info Version", i32 1}
 !5 = !{i32 1, !"wchar_size", i32 4}
-!6 = !{i32 1, !"min_enum_size", i32 4}
+!6 = !{i32 1, !"enumsize_buildattr", i32 2}
 !7 = !{!"clang version 3.6.0 "}

test/DebugInfo/ARM/multiple-constant-uses-drops-dbgloc.ll

 !7 = !{!8, !10}
 !8 = !DIGlobalVariable(name: "ch", scope: !0, file: !1, line: 1, type: !9, isLocal: false, isDefinition: true)
 !9 = !DIBasicType(name: "char", size: 8, align: 8, encoding: DW_ATE_unsigned_char)
 !10 = !DIGlobalVariable(name: "b", scope: !0, file: !1, line: 2, type: !11, isLocal: false, isDefinition: true)
 !11 = !DIBasicType(name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
 !12 = !{i32 2, !"Dwarf Version", i32 4}
 !13 = !{i32 2, !"Debug Info Version", i32 3}
 !14 = !{i32 1, !"wchar_size", i32 4}
-!15 = !{i32 1, !"min_enum_size", i32 4}
+!15 = !{i32 1, !"enumsize_buildattr", i32 2}
 !16 = !{!"clang version 3.7.0 (http://llvm.org/git/clang.git 9b0abb9df531ef7928c8182120e1869affca17d5) (http://llvm.org/git/llvm.git b1e759524dd94f7ce1e24935daed8383927e96c1)"}
 !17 = !DILocation(line: 6, column: 8, scope: !4)
 !18 = !DILocation(line: 7, column: 7, scope: !4)
 !19 = !DILocation(line: 8, column: 1, scope: !4)