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[PATCH] Reject pre/post inc/decrement in "m" input operands (PR middle-end/43690)


Hi!

We currently ICE in various ways when "m" operand has pre or post
increment/decrement.  We reject "m" (x + 1) and & which is roughly
what "m" does doesn't accept x++ or ++x either, so I think rejecting
it is the best thing to do.  The ICEs are because the FEs
don't mark the operand addressable, so we get invalid gimple.

In theory for POST increment/decrement we could instead just
mark their operand addressable, but for PRE increment/decrement
we still ICE with that badly.

What do you think about this?
Bootstrapped/regtested on x86_64-linux and i686-linux as usual.

2010-11-04  Jakub Jelinek  <jakub@redhat.com>

	PR middle-end/43690
	* gimplify.c (gimplify_asm_expr): If a "m" input is a
	{pre,post}{in,de}crement, fail.

	* c-c++-common/pr43690.c: New test.

--- gcc/gimplify.c.jj	2010-03-26 17:13:37.000000000 +0100
+++ gcc/gimplify.c	2010-04-12 11:35:52.000000000 +0200
@@ -4989,6 +4989,13 @@ gimplify_asm_expr (tree *expr_p, gimple_
       /* If the operand is a memory input, it should be an lvalue.  */
       if (!allows_reg && allows_mem)
 	{
+	  tree inputv = TREE_VALUE (link);
+	  STRIP_NOPS (inputv);
+	  if (TREE_CODE (inputv) == PREDECREMENT_EXPR
+	      || TREE_CODE (inputv) == PREINCREMENT_EXPR
+	      || TREE_CODE (inputv) == POSTDECREMENT_EXPR
+	      || TREE_CODE (inputv) == POSTINCREMENT_EXPR)
+	    TREE_VALUE (link) = error_mark_node;
 	  tret = gimplify_expr (&TREE_VALUE (link), pre_p, post_p,
 				is_gimple_lvalue, fb_lvalue | fb_mayfail);
 	  mark_addressable (TREE_VALUE (link));
--- gcc/testsuite/c-c++-common/pr43690.c.jj	2010-04-12 11:14:44.000000000 +0200
+++ gcc/testsuite/c-c++-common/pr43690.c	2010-04-12 11:37:33.000000000 +0200
@@ -0,0 +1,13 @@
+/* PR middle-end/43690 */
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+void
+foo (char *x)
+{
+  asm ("" : : "m" (x++));	/* { dg-error "is not directly addressable" } */
+  asm ("" : : "m" (++x));	/* { dg-error "is not directly addressable" } */
+  asm ("" : : "m" (x--));	/* { dg-error "is not directly addressable" } */
+  asm ("" : : "m" (--x));	/* { dg-error "is not directly addressable" } */
+  asm ("" : : "m" (x + 1));	/* { dg-error "is not directly addressable" } */
+}

	Jakub


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