[PATCH, RFC?] Verify that VCE(SSA_NAME) does not occur on any LHS

[Martin Jambor]

Hi,

when hunting down some gimple grammar problems in IL that IPA-SRA
produces, I stumbled upon the fact that VIEW_CONVERT_EXPRs of
SSA_NAMEs on the left hand sides of gimple assign and call statements
are not caught by the statement verifier.  So I added a check for that
to verify_types_in_gimple_reference which errors out for example when
fed the testcase in comment 5 of PR 42025 (on x86_64).

I have also changed verify_gimple_call to check the LHS with
verify_types_in_gimple_reference rather than with mere
is_gimple_lvalue.  I have looked carefully at the code and believe
that it is the correct thing to do but I would not be very surprised
if someone proved me wrong.

I have also bootstrapped and tested the patch below on x86_64-linux
with no regressions.  I would certainly like to commit a patch like
this when stage1 opens again.  I am not sure whether it is a good idea
to commit it now (now meaning after I fix the PR) during stage3 but
will gladly do it if a release manager agrees.  Nevertheless, I will
use it to test my IPA-SRA fixes right now and so am interested in any
feedback.

Thanks,

Martin


2009-11-16  Martin Jambor  <mjambor@suse.cz>

	* tree-cfg.c (verify_types_in_gimple_reference): Error out on V_C_E of
	an SSA_NAME if lvalue is required.
	(verify_gimple_call): Verify LHS with verify_types_in_gimple_reference
	rather than is_gimple_lvalue.
	
Index: mine/gcc/tree-cfg.c
===================================================================
--- mine.orig/gcc/tree-cfg.c
+++ mine/gcc/tree-cfg.c
@@ -2889,12 +2889,22 @@ verify_types_in_gimple_reference (tree e
 	  return true;
 	}
 
-      /* For VIEW_CONVERT_EXPRs which are allowed here, too, there
-	 is nothing to verify.  Gross mismatches at most invoke
-	 undefined behavior.  */
-      if (TREE_CODE (expr) == VIEW_CONVERT_EXPR
-	  && !handled_component_p (op))
-	return false;
+      if (TREE_CODE (expr) == VIEW_CONVERT_EXPR)
+	{
+	  /* For VIEW_CONVERT_EXPRs which are allowed here too, we only check
+	     that their operand is not an SSA name when requiring an lvalue
+	     (this usually means there is a SRA or IPA-SRA bug).  Otherwise
+	     there is nothing to verify, gross mismatches at most invoke
+	     undefined behavior.  */
+	  if (require_lvalue && TREE_CODE (op) == SSA_NAME)
+	    {
+	      error ("Conversion of an SSA_NAME on the left hand side.");
+	      debug_generic_stmt (expr);
+	      return true;
+	    }
+	  else if (!handled_component_p (op))
+	    return false;
+	}
 
       expr = op;
     }
@@ -2951,7 +2961,7 @@ verify_gimple_call (gimple stmt)
     }
 
   if (gimple_call_lhs (stmt)
-      && !is_gimple_lvalue (gimple_call_lhs (stmt)))
+      && verify_types_in_gimple_reference (gimple_call_lhs (stmt), true))
     {
       error ("invalid LHS in gimple call");
       return true;