[gcc r12-1654] [committed] More useless code elimination on the H8

[gcc r12-1654] [committed] More useless code elimination on the H8

[Jeff Law]

https://gcc.gnu.org/g:629cbc682a773e64c4bcb800ea98fb3051cd810c

commit r12-1654-g629cbc682a773e64c4bcb800ea98fb3051cd810c
Author: Jeff Law <jeffreyalaw@gmail.com>
Date:   Fri Jun 18 18:02:16 2021 -0400

    [committed] More useless code elimination on the H8
    
    gcc/
            * config/h8300/h8300.c (h8300_select_cc_mode): Handle SYMBOL_REF.
            * config/h8300/logical.md (<code><mode>3 logcial expander): Generate
            more efficient code when the source can be trivially simplified.

Diff:
---
 gcc/config/h8300/h8300.c    |  2 +-
 gcc/config/h8300/logical.md | 22 +++++++++++++++++++++-
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/gcc/config/h8300/h8300.c b/gcc/config/h8300/h8300.c
index 1077a2b6ae0..2b88325d2f7 100644
--- a/gcc/config/h8300/h8300.c
+++ b/gcc/config/h8300/h8300.c
@@ -1950,7 +1950,7 @@ h8300_select_cc_mode (enum rtx_code cond, rtx op0, rtx op1)
           || GET_CODE (op0) == NEG || GET_CODE (op0) == AND
           || GET_CODE (op0) == IOR || GET_CODE (op0) == XOR
           || GET_CODE (op0) == NOT || GET_CODE (op0) == ASHIFT
-	  || GET_CODE (op0) == MULT
+	  || GET_CODE (op0) == MULT || GET_CODE (op0) == SYMBOL_REF
 	  || GET_CODE (op0) == SIGN_EXTEND || GET_CODE (op0) == ZERO_EXTEND
 	  || REG_P (op0) || MEM_P (op0)))
     return CCZNmode;
diff --git a/gcc/config/h8300/logical.md b/gcc/config/h8300/logical.md
index cb4c6384bdf..07d36cf0ef4 100644
--- a/gcc/config/h8300/logical.md
+++ b/gcc/config/h8300/logical.md
@@ -4,7 +4,27 @@
 	(logicals:QHSI (match_operand:QHSI 1 "register_operand" "")
 		       (match_operand:QHSI 2 "h8300_src_operand" "")))]
   ""
-  "")
+  "
+  {
+    enum machine_mode mode = GET_MODE (operands[0]);
+    /* DImodes are not considered tieable, as a result operations involving
+       subregs of DImode objects are considered expensive which can prevent
+       CSE from doing obvious simplifications.
+
+       We may ultimately change what is tieable, but this is an immediate
+       workaround while we evaluate changes to tieable modes.
+
+       The key in terms of what we want to handle is then the result of
+       the operation is not a constant.  */
+    if ((<CODE> == AND && operands[2] == CONSTM1_RTX (mode))
+	|| (<CODE> == IOR && operands[2] == CONST0_RTX (mode))
+	|| (<CODE> == XOR && operands[2] == CONST0_RTX (mode))
+	|| ((<CODE> == AND || <CODE> == IOR) && operands[1] == operands[2]))
+      {
+	emit_move_insn (operands[0], operands[1]);
+	DONE;
+      }
+  }")
 
 ;; There's a ton of cleanup to do from here below.
 ;; ----------------------------------------------------------------------