Use DILexicalBlockFile, rather than DILexicalBlock, to track discriminator changes to ensure discriminator changes don't introduce new DWARF DW_TAG_lexical_blocks.

Somewhat unnoticed in the original implementation of discriminators, but
it could cause instructions to end up in new, small,
DW_TAG_lexical_blocks due to the use of DILexicalBlock to track
discriminator changes.

Instead, use DILexicalBlockFile which we already use to track file
changes without introducing new scopes, so it works well to track
discriminator changes in the same way.

llvm-svn: 216239

1 files changed, 3 insertions, 5 deletions

diff --git a/llvm/docs/SourceLevelDebugging.rst b/llvm/docs/SourceLevelDebugging.rst
index f76202ae053..f7b62cb0872 100644
--- a/llvm/docs/SourceLevelDebugging.rst
+++ b/llvm/docs/SourceLevelDebugging.rst
@@ -320,7 +320,6 @@ Block descriptors
     metadata, ;; Reference to context descriptor
     i32,      ;; Line number
     i32,      ;; Column number
-    i32,      ;; DWARF path discriminator value
     i32       ;; Unique ID to identify blocks from a template function
   }
 
@@ -334,6 +333,7 @@ lexical blocks at same depth.
     i32,      ;; Tag = 11 (DW_TAG_lexical_block)
     metadata, ;; Source directory (including trailing slash) & file pair
     metadata  ;; Reference to the scope we're annotating with a file change
+    i32,      ;; DWARF path discriminator value
   }
 
 This descriptor provides a wrapper around a lexical scope to handle file
@@ -733,8 +733,7 @@ Compiled to LLVM, this function would be represented like this:
   !15 = metadata !{i32 786688, metadata !16, metadata !"Z", metadata !5, i32 5,
                    metadata !11, i32 0, i32 0} ; [ DW_TAG_auto_variable ] [Z] \
                      [line 5]
-  !16 = metadata !{i32 786443, metadata !1, metadata !4, i32 4, i32 0, i32 0,
-                   i32 0} \
+  !16 = metadata !{i32 786443, metadata !1, metadata !4, i32 4, i32 0, i32 0} \
                    ; [ DW_TAG_lexical_block ] [/private/tmp/t.c]
   !17 = metadata !{i32 5, i32 0, metadata !16, null}
   !18 = metadata !{i32 6, i32 0, metadata !16, null}
@@ -786,8 +785,7 @@ scope information for the variable ``Z``.
 
 .. code-block:: llvm
 
-  !16 = metadata !{i32 786443, metadata !1, metadata !4, i32 4, i32 0, i32 0,
-                   i32 0}
+  !16 = metadata !{i32 786443, metadata !1, metadata !4, i32 4, i32 0, i32 0} \
                    ; [ DW_TAG_lexical_block ] [/private/tmp/t.c]
   !17 = metadata !{i32 5, i32 0, metadata !16, null}