[PATCH] xtensa: Make use of CLAMPS instruction if configured

[Takayuki 'January June' Suwa <jjsuwa_sys3175@yahoo.co.jp>]

This patch introduces the use of CLAMPS instruction when the instruction
is configured.

    /* example */
    int test(int a) {
      if (a < -512)
        return -512;
      if (a > 511)
        return 511;
      return a;
    }

    ;; prereq: TARGET_CLAMPS
    test:
	clamps	a2, a2, 9
	ret.n

gcc/ChangeLog:

	* config/xtensa/xtensa-protos.h (xtensa_match_CLAMPS_imms_p):
	New prototype.
	* config/xtensa/xtensa.cc (xtensa_match_CLAMPS_imms_p):
	New function.
	* config/xtensa/xtensa.h (TARGET_CLAMPS): New macro definition.
	* config/xtensa/xtensa.md (*xtensa_clamps): New insn pattern.
---
 gcc/config/xtensa/xtensa-protos.h |  1 +
 gcc/config/xtensa/xtensa.cc       | 13 +++++++++++
 gcc/config/xtensa/xtensa.h        |  1 +
 gcc/config/xtensa/xtensa.md       | 37 +++++++++++++++++++++++++++++++
 4 files changed, 52 insertions(+)

diff --git a/gcc/config/xtensa/xtensa-protos.h b/gcc/config/xtensa/xtensa-protos.h
index c81cf94323a..64cbf27c248 100644
--- a/gcc/config/xtensa/xtensa-protos.h
+++ b/gcc/config/xtensa/xtensa-protos.h
@@ -60,6 +60,7 @@ extern bool xtensa_tls_referenced_p (rtx);
 extern enum rtx_code xtensa_shlrd_which_direction (rtx, rtx);
 extern bool xtensa_split1_finished_p (void);
 extern void xtensa_split_DI_reg_imm (rtx *);
+extern bool xtensa_match_CLAMPS_imms_p (rtx, rtx);
 
 #ifdef TREE_CODE
 extern void init_cumulative_args (CUMULATIVE_ARGS *, int);
diff --git a/gcc/config/xtensa/xtensa.cc b/gcc/config/xtensa/xtensa.cc
index 5044bc25c2f..7287aa7a258 100644
--- a/gcc/config/xtensa/xtensa.cc
+++ b/gcc/config/xtensa/xtensa.cc
@@ -2611,6 +2611,19 @@ xtensa_emit_add_imm (rtx dst, rtx src, HOST_WIDE_INT imm, rtx scratch,
 }
 
 
+/* Return true if the constants used in the application of smin() following
+   smax() meet the specifications of the CLAMPS machine instruction.  */
+bool
+xtensa_match_CLAMPS_imms_p (rtx cst_max, rtx cst_min)
+{
+  int max, min;
+
+  return IN_RANGE (max = exact_log2 (-INTVAL (cst_max)), 7, 22)
+	 && IN_RANGE (min = exact_log2 (INTVAL (cst_min) + 1), 7, 22)
+	 && max == min;
+}
+
+
 /* Implement TARGET_CANNOT_FORCE_CONST_MEM.  */
 
 static bool
diff --git a/gcc/config/xtensa/xtensa.h b/gcc/config/xtensa/xtensa.h
index d4cd5def7b5..058602e44ee 100644
--- a/gcc/config/xtensa/xtensa.h
+++ b/gcc/config/xtensa/xtensa.h
@@ -35,6 +35,7 @@ along with GCC; see the file COPYING3.  If not see
 #define TARGET_NSA		XCHAL_HAVE_NSA
 #define TARGET_MINMAX		XCHAL_HAVE_MINMAX
 #define TARGET_SEXT		XCHAL_HAVE_SEXT
+#define TARGET_CLAMPS		XCHAL_HAVE_CLAMPS
 #define TARGET_BOOLEANS		XCHAL_HAVE_BOOLEANS
 #define TARGET_HARD_FLOAT	XCHAL_HAVE_FP
 #define TARGET_HARD_FLOAT_DIV	XCHAL_HAVE_FP_DIV
diff --git a/gcc/config/xtensa/xtensa.md b/gcc/config/xtensa/xtensa.md
index b60dec2447f..3521fa33b47 100644
--- a/gcc/config/xtensa/xtensa.md
+++ b/gcc/config/xtensa/xtensa.md
@@ -446,6 +446,43 @@
    (set_attr "mode"	"SI")
    (set_attr "length"	"3")])
 
+\f
+;; Signed clamp.
+
+(define_insn_and_split "*xtensa_clamps"
+  [(set (match_operand:SI 0 "register_operand" "=a")
+	(smax:SI (smin:SI (match_operand:SI 1 "register_operand" "r")
+			  (match_operand:SI 2 "const_int_operand" "i"))
+		 (match_operand:SI 3 "const_int_operand" "i")))]
+  "TARGET_CLAMPS
+   && xtensa_match_CLAMPS_imms_p (operands[3], operands[2])"
+  "#"
+  "&& 1"
+  [(set (match_dup 0)
+	(smin:SI (smax:SI (match_dup 1)
+			  (match_dup 3))
+		 (match_dup 2)))]
+  ""
+  [(set_attr "type"	"arith")
+   (set_attr "mode"	"SI")
+   (set_attr "length"	"3")])
+
+(define_insn "*xtensa_clamps"
+  [(set (match_operand:SI 0 "register_operand" "=a")
+	(smin:SI (smax:SI (match_operand:SI 1 "register_operand" "r")
+			  (match_operand:SI 2 "const_int_operand" "i"))
+		 (match_operand:SI 3 "const_int_operand" "i")))]
+  "TARGET_CLAMPS
+   && xtensa_match_CLAMPS_imms_p (operands[2], operands[3])"
+{
+  static char result[64];
+  sprintf (result, "clamps\t%%0, %%1, %d", floor_log2 (-INTVAL (operands[2])));
+  return result;
+}
+  [(set_attr "type"	"arith")
+   (set_attr "mode"	"SI")
+   (set_attr "length"	"3")])
+
 \f
 ;; Count redundant leading sign bits and leading/trailing zeros,
 ;; and find first bit.
-- 
2.30.2

(Totally off-topic, but do you know anything about the SALT/SALTU instructions?
I see them in the "Core Architecture Instructions" in a recent Cadence document
but not in slightly older Tensilica one...)