[gcc r12-2335] analyzer: use DECL_DEBUG_EXPR on SSA names for artificial vars

[gcc r12-2335] analyzer: use DECL_DEBUG_EXPR on SSA names for artificial vars

[David Malcolm]

https://gcc.gnu.org/g:e9711fe482b4abef0e7572809d3593631991276e

commit r12-2335-ge9711fe482b4abef0e7572809d3593631991276e
Author: David Malcolm <dmalcolm@redhat.com>
Date:   Thu Jul 15 15:02:42 2021 -0400

    analyzer: use DECL_DEBUG_EXPR on SSA names for artificial vars
    
    gcc/analyzer/ChangeLog:
            * analyzer.cc (fixup_tree_for_diagnostic_1): Use DECL_DEBUG_EXPR
            if it's available.
            * engine.cc (readability): Likewise.
    
    Signed-off-by: David Malcolm <dmalcolm@redhat.com>

Diff:
---
 gcc/analyzer/analyzer.cc |  9 +++++++--
 gcc/analyzer/engine.cc   | 19 ++++++++++++++++---
 2 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/gcc/analyzer/analyzer.cc b/gcc/analyzer/analyzer.cc
index 12c03f6cfbd..a8ee1a1a2dc 100644
--- a/gcc/analyzer/analyzer.cc
+++ b/gcc/analyzer/analyzer.cc
@@ -165,8 +165,13 @@ fixup_tree_for_diagnostic_1 (tree expr, hash_set<tree> *visited)
       && TREE_CODE (expr) == SSA_NAME
       && (SSA_NAME_VAR (expr) == NULL_TREE
 	  || DECL_ARTIFICIAL (SSA_NAME_VAR (expr))))
-    if (tree expr2 = maybe_reconstruct_from_def_stmt (expr, visited))
-      return expr2;
+    {
+      if (tree var = SSA_NAME_VAR (expr))
+	if (VAR_P (var) && DECL_HAS_DEBUG_EXPR_P (var))
+	  return DECL_DEBUG_EXPR (var);
+      if (tree expr2 = maybe_reconstruct_from_def_stmt (expr, visited))
+	return expr2;
+    }
   return expr;
 }
 
diff --git a/gcc/analyzer/engine.cc b/gcc/analyzer/engine.cc
index 01b83a4ef28..8f3e7f781b2 100644
--- a/gcc/analyzer/engine.cc
+++ b/gcc/analyzer/engine.cc
@@ -527,9 +527,22 @@ readability (const_tree expr)
     case SSA_NAME:
       {
 	if (tree var = SSA_NAME_VAR (expr))
-	  /* Slightly favor the underlying var over the SSA name to
-	     avoid having them compare equal.  */
-	  return readability (var) - 1;
+	  {
+	    if (DECL_ARTIFICIAL (var))
+	      {
+		/* If we have an SSA name for an artificial var,
+		   only use it if it has a debug expr associated with
+		   it that fixup_tree_for_diagnostic can use.  */
+		if (VAR_P (var) && DECL_HAS_DEBUG_EXPR_P (var))
+		  return readability (DECL_DEBUG_EXPR (var)) - 1;
+	      }
+	    else
+	      {
+		/* Slightly favor the underlying var over the SSA name to
+		   avoid having them compare equal.  */
+		return readability (var) - 1;
+	      }
+	  }
 	/* Avoid printing '<unknown>' for SSA names for temporaries.  */
 	return -1;
       }