[gcc r16-5818] MIPS: Add WSBW instruction to perform bswapsi2

[YunQiang Su]

https://gcc.gnu.org/g:0591ab53005b31a0d780d683004d84a4633ac35f

commit r16-5818-g0591ab53005b31a0d780d683004d84a4633ac35f
Author: David Guillen Fandos <david@davidgf.net>
Date:   Fri Sep 19 18:48:10 2025 +0200

    MIPS: Add WSBW instruction to perform bswapsi2
    
    gcc/ChangeLog:
    
            * config/mips/mips.h (ISA_HAS_WSBW): Defined a new macro.
            * config/mips/mips.md (bswapsi2): Add new instruction.
            (wsbwsi2): Replace with expand to support both wsbw and wsbh.
    
    gcc/testsuite/ChangeLog:
    
            * gcc.target/mips/bswap-7.c: New test.
    
    Signed-off-by: David Guillen Fandos <david@davidgf.net>

Diff:
---
 gcc/config/mips/mips.h                  |  3 +++
 gcc/config/mips/mips.md                 | 29 +++++++++++++++++++++--------
 gcc/testsuite/gcc.target/mips/bswap-7.c |  9 +++++++++
 3 files changed, 33 insertions(+), 8 deletions(-)

diff --git a/gcc/config/mips/mips.h b/gcc/config/mips/mips.h
index a78f42148489..7d1fc6552d6f 100644
--- a/gcc/config/mips/mips.h
+++ b/gcc/config/mips/mips.h
@@ -1263,6 +1263,9 @@ struct mips_cpu_info {
 #define ISA_HAS_WSBH		((mips_isa_rev >= 2 && !TARGET_MIPS16)  \
 				  || TARGET_ALLEGREX)
 
+/* Similar to WSBH but for 32 bit words (byte swap within a word). */
+#define ISA_HAS_WSBW		(TARGET_ALLEGREX)
+
 /* ISA has data prefetch instructions.  This controls use of 'pref'.  */
 #define ISA_HAS_PREFETCH	((ISA_MIPS4				\
 				  || TARGET_LOONGSON_2EF		\
diff --git a/gcc/config/mips/mips.md b/gcc/config/mips/mips.md
index d9aee8189596..939e51719297 100644
--- a/gcc/config/mips/mips.md
+++ b/gcc/config/mips/mips.md
@@ -6041,16 +6041,29 @@
   "wsbh\t%0,%1"
   [(set_attr "type" "shift")])
 
-(define_insn_and_split "bswapsi2"
+(define_expand "bswapsi2"
+  [(set (match_operand:SI 0 "register_operand" "=d")
+    (bswap:SI (match_operand:SI 1 "register_operand" "d")))]
+  "ISA_HAS_WSBW || (ISA_HAS_WSBH && ISA_HAS_ROR)"
+{
+  if (ISA_HAS_WSBW) {
+    emit_insn (gen_wsbwsi2 (operands[0], operands[1]));
+  }
+  else
+  {
+    rtx tmp = gen_reg_rtx (SImode);
+    emit_insn (gen_wsbh (tmp, operands[1]));
+    emit_insn (gen_rotrsi3 (operands[0], tmp, GEN_INT(16)));
+  }
+  DONE;
+})
+
+(define_insn "wsbwsi2"
   [(set (match_operand:SI 0 "register_operand" "=d")
 	(bswap:SI (match_operand:SI 1 "register_operand" "d")))]
-  "ISA_HAS_WSBH && ISA_HAS_ROR"
-  "#"
-  "&& 1"
-  [(set (match_dup 0) (unspec:SI [(match_dup 1)] UNSPEC_WSBH))
-   (set (match_dup 0) (rotatert:SI (match_dup 0) (const_int 16)))]
-  ""
-  [(set_attr "insn_count" "2")])
+  "ISA_HAS_WSBW"
+  "wsbw\t%0,%1"
+  [(set_attr "type" "shift")])
 
 (define_insn_and_split "bswapdi2"
   [(set (match_operand:DI 0 "register_operand" "=d")
diff --git a/gcc/testsuite/gcc.target/mips/bswap-7.c b/gcc/testsuite/gcc.target/mips/bswap-7.c
new file mode 100644
index 000000000000..c1f923eec021
--- /dev/null
+++ b/gcc/testsuite/gcc.target/mips/bswap-7.c
@@ -0,0 +1,9 @@
+/* { dg-options "-march=allegrex" } */
+
+NOMIPS16 unsigned int
+foo (unsigned int x)
+{
+  return __builtin_bswap32 (x);
+}
+
+/* { dg-final { scan-assembler "\twsbw\t" } } */