[PATCH] Fix expand_binop (PR middle-end/88032)

[Jakub Jelinek <jakub@redhat.com>]

Hi!

On Wed, Nov 14, 2018 at 09:35:30AM -0700, Jeff Law wrote:
> +	* optabs.c (expand_binop): Pass INT_MODE to operand_subword_force
> +	iff the operand is a constant.

This broke gcc.target/i386/pr80173.c testcase.  The problem is
that while operand_subword handles VOIDmode last argument just fine
by using GET_MODE (op), so it is only important to use non-VOIDmode if
op has VOIDmode.  But, operand_subword_force actually has a different
behavior, if mode is VOIDmode (or BLKmode), it acts just as operand_subword
followed by assertion that it succeeded, rather than by trying to deal with
failed operand_subword by forcing it into a pseudo.

In the testcase, op is a hard register, on which operand_subword fails, but
if it is forced into pseudo, it succeeds.

The following patch arranges it by never passing VOIDmode to
operand_subword_force, pass int_mode as previously if opN has VOIDmode, but
instead of passing VOIDmode otherwise pass the actual mode of the opN
operand.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2018-11-16  Jakub Jelinek  <jakub@redhat.com>

	PR middle-end/88032
	* optabs.c (expand_binop): For op0_mode use GET_MODE (op0), unless it
	is VOIDmode, in which case use int_mode.  Similarly for op1_mode.

--- gcc/optabs.c.jj	2018-11-14 17:42:53.044049213 +0100
+++ gcc/optabs.c	2018-11-15 15:45:35.949378049 +0100
@@ -1377,8 +1377,12 @@ expand_binop (machine_mode mode, optab b
       start_sequence ();
 
       /* Do the actual arithmetic.  */
-      enum machine_mode op0_mode = CONSTANT_P (op0) ? int_mode : VOIDmode;
-      enum machine_mode op1_mode = CONSTANT_P (op1) ? int_mode : VOIDmode;
+      enum machine_mode op0_mode = GET_MODE (op0);
+      enum machine_mode op1_mode = GET_MODE (op1);
+      if (op0_mode == VOIDmode)
+	op0_mode = int_mode;
+      if (op1_mode == VOIDmode)
+	op1_mode = int_mode;
       for (i = 0; i < GET_MODE_BITSIZE (int_mode) / BITS_PER_WORD; i++)
 	{
 	  rtx target_piece = operand_subword (target, i, 1, int_mode);


	Jakub