docs: Document function-attached metadata and IR changes from r252219.

llvm-svn: 252268

llvm/docs/LangRef.rst

@@ -640,6 +640,7 @@ an optional :ref:`comdat <langref_comdats>`,
 an optional :ref:`garbage collector name <gc>`, an optional :ref:`prefix <prefixdata>`,
 an optional :ref:`prologue <prologuedata>`,
 an optional :ref:`personality <personalityfn>`,
+an optional list of attached :ref:`metadata <metadata>`,
 an opening curly brace, a list of basic blocks, and a closing curly brace.
 
 LLVM function declarations consist of the "``declare``" keyword, an
@@ -688,7 +689,7 @@ Syntax::
            <ResultType> @<FunctionName> ([argument list])
            [unnamed_addr] [fn Attrs] [section "name"] [comdat [($name)]]
            [align N] [gc] [prefix Constant] [prologue Constant]
-           [personality Constant] { ... }
+           [personality Constant] (!name !N)* { ... }
 
 The argument list is a comma separated sequence of arguments where each
 argument is of the following form:
@@ -3624,13 +3625,22 @@ function is using two metadata arguments:
 
     call void @llvm.dbg.value(metadata !24, i64 0, metadata !25)
 
-Metadata can be attached with an instruction. Here metadata ``!21`` is
-attached to the ``add`` instruction using the ``!dbg`` identifier:
+Metadata can be attached to an instruction. Here metadata ``!21`` is attached
+to the ``add`` instruction using the ``!dbg`` identifier:
 
 .. code-block:: llvm
 
     %indvar.next = add i64 %indvar, 1, !dbg !21
 
+Metadata can also be attached to a function definition. Here metadata ``!22``
+is attached to the ``foo`` function using the ``!dbg`` identifier:
+
+.. code-block:: llvm
+
+    define void @foo() !dbg !22 {
+      ret void
+    }
+
 More information about specific metadata nodes recognized by the
 optimizers and code generator is found below.
 
@@ -3901,20 +3911,26 @@ All global variables should be referenced by the `globals:` field of a
 DISubprogram
 """"""""""""
 
-``DISubprogram`` nodes represent functions from the source language. The
-``variables:`` field points at :ref:`variables <DILocalVariable>` that must be
-retained, even if their IR counterparts are optimized out of the IR. The
-``type:`` field must point at an :ref:`DISubroutineType`.
+``DISubprogram`` nodes represent functions from the source language. A
+``DISubprogram`` may be attached to a function definition using ``!dbg``
+metadata. The ``variables:`` field points at :ref:`variables <DILocalVariable>`
+that must be retained, even if their IR counterparts are optimized out of
+the IR. The ``type:`` field must point at an :ref:`DISubroutineType`.
 
 .. code-block:: llvm
 
-    !0 = !DISubprogram(name: "foo", linkageName: "_Zfoov", scope: !1,
-                       file: !2, line: 7, type: !3, isLocal: true,
-                       isDefinition: false, scopeLine: 8, containingType: !4,
-                       virtuality: DW_VIRTUALITY_pure_virtual, virtualIndex: 10,
-                       flags: DIFlagPrototyped, isOptimized: true,
-                       function: void ()* @_Z3foov,
-                       templateParams: !5, declaration: !6, variables: !7)
+    define void @_Z3foov() !dbg !0 {
+      ...
+    }
+
+    !0 = distinct !DISubprogram(name: "foo", linkageName: "_Zfoov", scope: !1,
+                                file: !2, line: 7, type: !3, isLocal: true,
+                                isDefinition: false, scopeLine: 8,
+                                containingType: !4,
+                                virtuality: DW_VIRTUALITY_pure_virtual,
+                                virtualIndex: 10, flags: DIFlagPrototyped,
+                                isOptimized: true, templateParams: !5,
+                                declaration: !6, variables: !7)
 
 .. _DILexicalBlock:
 

llvm/docs/SourceLevelDebugging.rst

@@ -231,7 +231,7 @@ Compiled to LLVM, this function would be represented like this:
 .. code-block:: llvm
 
   ; Function Attrs: nounwind ssp uwtable
-  define void @foo() #0 {
+  define void @foo() #0 !dbg !4 {
   entry:
     %X = alloca i32, align 4
     %Y = alloca i32, align 4
@@ -263,7 +263,7 @@ Compiled to LLVM, this function would be represented like this:
   !1 = !DIFile(filename: "/dev/stdin", directory: "/Users/dexonsmith/data/llvm/debug-info")
   !2 = !{}
   !3 = !{!4}
-  !4 = distinct !DISubprogram(name: "foo", scope: !1, file: !1, line: 1, type: !5, isLocal: false, isDefinition: true, scopeLine: 1, isOptimized: false, function: void ()* @foo, variables: !2)
+  !4 = distinct !DISubprogram(name: "foo", scope: !1, file: !1, line: 1, type: !5, isLocal: false, isDefinition: true, scopeLine: 1, isOptimized: false, variables: !2)
   !5 = !DISubroutineType(types: !6)
   !6 = !{null}
   !7 = !{i32 2, !"Dwarf Version", i32 2}
@@ -304,10 +304,9 @@ scope information for the variable ``X``.
 .. code-block:: llvm
 
   !14 = !DILocation(line: 2, column: 9, scope: !4)
-  !4 = !DISubprogram(name: "foo", scope: !1, file: !1, line: 1, type: !5,
-                     isLocal: false, isDefinition: true, scopeLine: 1,
-                     isOptimized: false, function: void ()* @foo,
-                     variables: !2)
+  !4 = distinct !DISubprogram(name: "foo", scope: !1, file: !1, line: 1, type: !5,
+                              isLocal: false, isDefinition: true, scopeLine: 1,
+                              isOptimized: false, variables: !2)
 
 Here ``!14`` is metadata providing `location information
 <LangRef.html#dilocation>`_.  In this example, scope is encoded by ``!4``, a
@@ -463,12 +462,12 @@ a C/C++ front-end would generate the following descriptors:
   !4 = !DISubprogram(name: "main", scope: !1, file: !1, line: 1, type: !5,
                      isLocal: false, isDefinition: true, scopeLine: 1,
                      flags: DIFlagPrototyped, isOptimized: false,
-                     function: i32 (i32, i8**)* @main, variables: !2)
+                     variables: !2)
 
   ;;
   ;; Define the subprogram itself.
   ;;
-  define i32 @main(i32 %argc, i8** %argv) {
+  define i32 @main(i32 %argc, i8** %argv) !dbg !4 {
   ...
   }