[26/77] Use is_a <scalar_int_mode> in subreg/extract simplifications

This patch adds is_a <scalar_int_mode> checks to various places that
were optimising subregs or extractions in ways that only made sense
for scalar integers.  Often the subreg transformations were looking
for extends, truncates or shifts and trying to remove the subreg, which
wouldn't be correct if the SUBREG_REG was a vector rather than a scalar.

The simplify_binary_operation_1 part also removes a redundant:

  GET_MODE (opleft) == GET_MODE (XEXP (opright, 0))

since this must be true for:

  (ior A (lshifrt B ...))  A == opleft, B == XEXP (opright, 0)

2017-08-30  Richard Sandiford  <richard.sandiford@linaro.org>
	    Alan Hayward  <alan.hayward@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

gcc/
	* combine.c (find_split_point): Add is_a <scalar_int_mode> checks.
	(make_compound_operation_int): Likewise.
	(change_zero_ext): Likewise.
	* expr.c (convert_move): Likewise.
	(convert_modes): Likewise.
	* fwprop.c (forward_propagate_subreg): Likewise.
	* loop-iv.c (get_biv_step_1): Likewise.
	* optabs.c (widen_operand): Likewise.
	* postreload.c (move2add_valid_value_p): Likewise.
	* recog.c (simplify_while_replacing): Likewise.
	* simplify-rtx.c (simplify_unary_operation_1): Likewise.
	(simplify_binary_operation_1): Likewise.  Remove redundant
	mode equality check.

Co-Authored-By: Alan Hayward <alan.hayward@arm.com>
Co-Authored-By: David Sherwood <david.sherwood@arm.com>

From-SVN: r251478

1 files changed, 11 insertions, 6 deletions

diff --git a/gcc/expr.c b/gcc/expr.c
index 225b8c2..ce5f42e 100644
--- a/gcc/expr.c
+++ b/gcc/expr.c
@@ -239,11 +239,14 @@ convert_move (rtx to, rtx from, int unsignedp)
      the required extension, strip it.  We don't handle such SUBREGs as
      TO here.  */
 
-  if (GET_CODE (from) == SUBREG && SUBREG_PROMOTED_VAR_P (from)
+  scalar_int_mode to_int_mode;
+  if (GET_CODE (from) == SUBREG
+      && SUBREG_PROMOTED_VAR_P (from)
+      && is_a <scalar_int_mode> (to_mode, &to_int_mode)
       && (GET_MODE_PRECISION (GET_MODE (SUBREG_REG (from)))
-	  >= GET_MODE_PRECISION (to_mode))
+	  >= GET_MODE_PRECISION (to_int_mode))
       && SUBREG_CHECK_PROMOTED_SIGN (from, unsignedp))
-    from = gen_lowpart (to_mode, from), from_mode = to_mode;
+    from = gen_lowpart (to_int_mode, from), from_mode = to_int_mode;
 
   gcc_assert (GET_CODE (to) != SUBREG || !SUBREG_PROMOTED_VAR_P (to));
 
@@ -635,10 +638,12 @@ convert_modes (machine_mode mode, machine_mode oldmode, rtx x, int unsignedp)
   /* If FROM is a SUBREG that indicates that we have already done at least
      the required extension, strip it.  */
 
-  if (GET_CODE (x) == SUBREG && SUBREG_PROMOTED_VAR_P (x)
-      && GET_MODE_SIZE (GET_MODE (SUBREG_REG (x))) >= GET_MODE_SIZE (mode)
+  if (GET_CODE (x) == SUBREG
+      && SUBREG_PROMOTED_VAR_P (x)
+      && is_a <scalar_int_mode> (mode, &int_mode)
+      && GET_MODE_SIZE (GET_MODE (SUBREG_REG (x))) >= GET_MODE_SIZE (int_mode)
       && SUBREG_CHECK_PROMOTED_SIGN (x, unsignedp))
-    x = gen_lowpart (mode, SUBREG_REG (x));
+    x = gen_lowpart (int_mode, SUBREG_REG (x));
 
   if (GET_MODE (x) != VOIDmode)
     oldmode = GET_MODE (x);