[patch] Couple of tweaks to the gimplifier

[Eric Botcazou]

Hi,

the attached patch makes a couple of tweaks to the gimplifier in order to help 
Ada, but I think that they are of general usefulness:

  1) Set TREE_THIS_NOTRAP on the INDIRECT_REF built for VLA decls.  This is
     correct since stack memory isn't considered as trapping in the IL.

  2) Improve gimplification of complex conditions in COND_EXPR.  They are
     naturally generated by the Ada compiler and the patch avoids emitting
     redundant branches in GIMPLE, visible at -O0 for the testcase:

procedure P (B : Boolean; S1, S2 : String) is
begin
  if B and then S1 & S2 = "toto" then
    raise Program_Error;
  end if;
end;

@@ -158,21 +158,12 @@
        movl    %r12d, %eax
        subl    %ebx, %eax
        cmpl    $3, %eax
-       jne     .L33
+       jne     .L18
        .loc 1 3 0 discriminator 1
        movq    -40(%rbp), %rax
        movl    (%rax), %eax
        cmpl    $1869901684, %eax
-       jne     .L33
-       .loc 1 3 0 discriminator 2
-       movl    $1, %eax
-       jmp     .L34
-.L33:
-       movl    $0, %eax
-.L34:
-       .loc 1 3 0 discriminator 3
-       testb   %al, %al
-       je      .L18
+       jne     .L18
        .loc 1 4 0 is_stmt 1
        movl    $4, %esi
        movl    $.LC0, %edi

Bootstrapped/regtested on x86_64-suse-linux, OK for the mainline?


2011-03-21  Eric Botcazou  <ebotca...@adacore.com>

        * gimplify.c (gimplify_vla_decl): Set TREE_THIS_NOTRAP flag.
        (gimplify_cond_expr): Gimplify COMPOUND_EXPR conditions.


-- 
Eric Botcazou

Index: gimplify.c
===================================================================
--- gimplify.c	(revision 171044)
+++ gimplify.c	(working copy)
@@ -1322,6 +1322,7 @@ gimplify_vla_decl (tree decl, gimple_seq
   addr = create_tmp_var (ptr_type, get_name (decl));
   DECL_IGNORED_P (addr) = 0;
   t = build_fold_indirect_ref (addr);
+  TREE_THIS_NOTRAP (t) = 1;
   SET_DECL_VALUE_EXPR (decl, t);
   DECL_HAS_VALUE_EXPR_P (decl) = 1;
 
@@ -2981,6 +2982,11 @@ gimplify_cond_expr (tree *expr_p, gimple
       return GS_ALL_DONE;
     }
 
+  /* Remove any COMPOUND_EXPR so the following cases will be caught.  */
+  STRIP_TYPE_NOPS (TREE_OPERAND (expr, 0));
+  if (TREE_CODE (TREE_OPERAND (expr, 0)) == COMPOUND_EXPR)
+    gimplify_compound_expr (&TREE_OPERAND (expr, 0), pre_p, true);
+
   /* Make sure the condition has BOOLEAN_TYPE.  */
   TREE_OPERAND (expr, 0) = gimple_boolify (TREE_OPERAND (expr, 0));