[backport proposed fix for PR52773 on M68K <mikpe@it.uu.se>]

List-Archive: <http://gcc.gnu.org/ml/gcc-patches/>
Date: Wed, 19 Jun 2013 19:39:03 +0200
From: Bernd Schmidt <bernds at codesourcery dot com>
Subject: CALL_INSN_FUNCTION_USAGE fix, PR52773

This is bug that triggers on m68k. The loop unroller creates a MULT
expression and tries to force it into a register, which causes a libcall
to be generated. Since args are pushed we create a
  (use (mem (plus virtual_outgoing_args scratch)))
in CALL_INSN_FUNCTION_USAGE. Since we're past vregs, the
virtual_outgoing_args rtx survives to reload, which blows up.

Fixed by just using stack_pointer_rtx, since we use a scratch anyway
rather than a known offset. I also noticed that we actually add two of
these USEs, so I've fixed that as well.

Bootstrapped and tested on x86_64-linux, ok?


Bernd

--- gcc-4.8.1/gcc/calls.c.~1~	2013-01-12 00:39:18.000000000 +0100
+++ gcc-4.8.1/gcc/calls.c	2013-06-21 13:03:26.365529168 +0200
@@ -3601,6 +3601,7 @@ emit_library_call_value_1 (int retval, r
   int reg_parm_stack_space = 0;
   int needed;
   rtx before_call;
+  bool have_push_fusage;
   tree tfom;			/* type_for_mode (outmode, 0) */
 
 #ifdef REG_PARM_STACK_SPACE
@@ -3954,6 +3955,8 @@ emit_library_call_value_1 (int retval, r
 
   /* Push the args that need to be pushed.  */
 
+  have_push_fusage = false;
+
   /* ARGNUM indexes the ARGVEC array in the order in which the arguments
      are to be pushed.  */
   for (count = 0; count < nargs; count++, argnum += inc)
@@ -4044,14 +4047,19 @@ emit_library_call_value_1 (int retval, r
 	  if (argblock)
 	    use = plus_constant (Pmode, argblock,
 				 argvec[argnum].locate.offset.constant);
+	  else if (have_push_fusage)
+	    continue;
 	  else
-	    /* When arguments are pushed, trying to tell alias.c where
-	       exactly this argument is won't work, because the
-	       auto-increment causes confusion.  So we merely indicate
-	       that we access something with a known mode somewhere on
-	       the stack.  */
-	    use = gen_rtx_PLUS (Pmode, virtual_outgoing_args_rtx,
-				gen_rtx_SCRATCH (Pmode));
+	    {
+	      /* When arguments are pushed, trying to tell alias.c where
+		 exactly this argument is won't work, because the
+		 auto-increment causes confusion.  So we merely indicate
+		 that we access something with a known mode somewhere on
+		 the stack.  */
+	      use = gen_rtx_PLUS (Pmode, stack_pointer_rtx,
+				  gen_rtx_SCRATCH (Pmode));
+	      have_push_fusage = true;
+	    }
 	  use = gen_rtx_MEM (argvec[argnum].mode, use);
 	  use = gen_rtx_USE (VOIDmode, use);
 	  call_fusage = gen_rtx_EXPR_LIST (VOIDmode, use, call_fusage);
--- gcc-4.8.1/gcc/testsuite/gcc.c-torture/compile/pr52773.c.~1~	1970-01-01 01:00:00.000000000 +0100
+++ gcc-4.8.1/gcc/testsuite/gcc.c-torture/compile/pr52773.c	2013-06-21 13:03:26.365529168 +0200
@@ -0,0 +1,16 @@
+/* pr52773.c */
+
+struct s {
+    short x;
+    short _pad[2];
+};
+
+static short mat_a_x;
+
+void transform(const struct s *src, struct s *dst, int n)
+{
+    int i;
+
+    for (i = 0; i < n; ++i)
+	dst[i].x = (src[i].x * mat_a_x) >> 6;
+}