[xstormy16 PATCH] Add support for byte and word swapping instructions.

["Roger Sayle" <roger@nextmovesoftware.com>]

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This patch adds support for xstormy16's swpb (swap bytes) and swpw (swap
words) instructions.  The most obvious application of these to implement
the __builtin_bswap16 and __builtin_bswap32 intrinsics.

Currently, __builtin_bswap16 is implemented as:
foo:    mov r7,r2
        shl r7,#8
        shr r2,#8
        or r2,r7
        ret

but with this patch becomes:
foo:    swpb r2
        ret

Likewise, __builtin_bswap32 now becomes:
foo:    swpb r2 | swpb r3 | swpw r2,r3
        ret

Finally, the swpw instruction on its own can be used to exchange
two word mode registers without a temporary, so a new pattern and
peephole2 have been added to catch this.  As described in the
PR rtl-optimization/106518, register allocation can (in theory)
be more efficient on targets that provide a swap/exchange instruction.
The slightly unusual swap<mode> naming matches that used in i386.md.

This patch has been tested by building a cross-compiler to xstormy16-elf
from x86_64-pc-linux-gnu, and confirming the new test cases pass.
Ok for mainline?


2024-04-25  Roger Sayle  <roger@nextmovesoftware.com>

gcc/ChangeLog
	* config/stormy16/stormy16.md (bswaphi2): New define_insn.
	(bswapsi2): New define_insn.
	(swaphi): New define_insn to exchange two registers (swpw).
	(define_peephole2): Recognize exchange of registers as swaphi.

gcc/testsuite/ChangeLog
	* gcc.target/xstormy16/bswap16.c: New test case.
	* gcc.target/xstormy16/bswap32.c: Likewise.
	* gcc.target/xstormy16/swpb.c: Likewise.
	* gcc.target/xstormy16/swpw-1.c: Likewise.
	* gcc.target/xstormy16/swpw-2.c: Likewise.

Thanks in advance,
Roger
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diff --git a/gcc/config/stormy16/stormy16.md b/gcc/config/stormy16/stormy16.md
index fd52588..4c2cff2 100644
--- a/gcc/config/stormy16/stormy16.md
+++ b/gcc/config/stormy16/stormy16.md
@@ -1265,3 +1265,39 @@
   "bp %1,#7,%l0"
   [(set_attr "length" "4")
    (set_attr "psw_operand" "nop")])
+
+(define_insn "bswaphi2"
+  [(set (match_operand:HI 0 "register_operand" "=r")
+	(bswap:HI (match_operand:HI 1 "register_operand" "0")))]
+  ""
+  "swpb %0")
+
+(define_insn "bswapsi2"
+  [(set (match_operand:SI 0 "register_operand" "=r")
+	(bswap:SI (match_operand:SI 1 "register_operand" "0")))]
+  ""
+  "swpb %0 | swpb %h0 | swpw %0,%h0"
+  [(set_attr "length" "6")])
+
+(define_insn "swaphi"
+  [(set (match_operand:HI 0 "register_operand" "+r")
+	(match_operand:HI 1 "register_operand" "+r"))
+   (set (match_dup 1)
+	(match_dup 0))]
+  ""
+  "swpw %0,%1")
+
+(define_peephole2
+  [(set (match_operand:HI 0 "register_operand")
+	(match_operand:HI 1 "register_operand"))
+   (set (match_dup 1)
+	(match_operand:HI 2 "register_operand"))
+   (set (match_dup 2)
+	(match_dup 0))]
+  "REGNO (operands[0]) != REGNO (operands[1])
+   && REGNO (operands[0]) != REGNO (operands[2])
+   && REGNO (operands[1]) != REGNO (operands[2])
+   && peep2_reg_dead_p (3, operands[0])"
+  [(parallel [(set (match_dup 2) (match_dup 1))
+              (set (match_dup 1) (match_dup 2))])])
+
diff --git a/gcc/testsuite/gcc.target/xstormy16/bswap16.c b/gcc/testsuite/gcc.target/xstormy16/bswap16.c
new file mode 100644
index 0000000..cf6795f
--- /dev/null
+++ b/gcc/testsuite/gcc.target/xstormy16/bswap16.c
@@ -0,0 +1,9 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+unsigned short foo(unsigned short x)
+{
+  return __builtin_bswap16 (x);
+}
+
+/* { dg-final { scan-assembler "swpb r2" } } */
diff --git a/gcc/testsuite/gcc.target/xstormy16/bswap32.c b/gcc/testsuite/gcc.target/xstormy16/bswap32.c
new file mode 100644
index 0000000..3287e4d
--- /dev/null
+++ b/gcc/testsuite/gcc.target/xstormy16/bswap32.c
@@ -0,0 +1,9 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+unsigned long foo(unsigned long x)
+{
+  return __builtin_bswap32 (x);
+}
+
+/* { dg-final { scan-assembler "swpb" } } */
diff --git a/gcc/testsuite/gcc.target/xstormy16/swpb.c b/gcc/testsuite/gcc.target/xstormy16/swpb.c
new file mode 100644
index 0000000..8ea8ff7
--- /dev/null
+++ b/gcc/testsuite/gcc.target/xstormy16/swpb.c
@@ -0,0 +1,9 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+unsigned short foo(unsigned short x)
+{
+  return (x>>8) | (x<<8);
+}
+
+/* { dg-final { scan-assembler "swpb r2" } } */
diff --git a/gcc/testsuite/gcc.target/xstormy16/swpw-1.c b/gcc/testsuite/gcc.target/xstormy16/swpw-1.c
new file mode 100644
index 0000000..bde540d
--- /dev/null
+++ b/gcc/testsuite/gcc.target/xstormy16/swpw-1.c
@@ -0,0 +1,8 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+void ext(int x, int y);
+
+void foo(int x, int y) { ext(y,x); }
+
+/* { dg-final { scan-assembler "swpw r3,r2" } } */
diff --git a/gcc/testsuite/gcc.target/xstormy16/swpw-2.c b/gcc/testsuite/gcc.target/xstormy16/swpw-2.c
new file mode 100644
index 0000000..b8d637b
--- /dev/null
+++ b/gcc/testsuite/gcc.target/xstormy16/swpw-2.c
@@ -0,0 +1,14 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+void ext(int x, int y);
+
+void foo(int x, int y)
+{
+  int t1 = x ^ y;
+  int t2 = t1 ^ x;
+  int t3 = t1 ^ y;
+  ext(t2,t3);
+}
+
+/* { dg-final { scan-assembler "swpw r3,r2" } } */