[gcc r14-8499] arm: Add pattern for bswap + rotate -> rev16 [Bug 108933]

[gcc r14-8499] arm: Add pattern for bswap + rotate -> rev16 [Bug 108933]

[Richard Earnshaw]

https://gcc.gnu.org/g:bad991a1c5960e90c4686a9362a1258ef29e195b

commit r14-8499-gbad991a1c5960e90c4686a9362a1258ef29e195b
Author: Matthieu Longo <matthieu.longo@arm.com>
Date:   Mon Jan 29 15:54:35 2024 +0000

    arm: Add pattern for bswap + rotate -> rev16 [Bug 108933]
    
    The rev16 pattern was not recognised anymore as a change in the bswap
    tree pass was introducing a new GIMPLE form, not recognized by the
    assembly final transformation pass.
    
    Also, fix the output patterns for arm_rev16si_alt[12] to correctly
    handle the instructions being made conditional.
    
    More details in the PR.
    
    gcc/ChangeLog:
    
            PR target/108933
            * config/arm/arm.md (arm_rev16si2): Convert to define_insn.
            Correct generated RTL.
            (arm_rev16si2_alt1): Correctly handle conditional execution.
            (arm_rev16si2_alt2): Likewise.
    
    gcc/testsuite/ChangeLog:
    
            PR target/108933
            * gcc.target/arm/rev16.c: Moved to...
            * gcc.target/arm/rev16_1.c: ...here.
            * gcc.target/arm/rev16_2.c: New test to check that rev16 is emitted.

Diff:
---
 gcc/config/arm/arm.md                              | 31 ++++++++++++++--------
 .../gcc.target/arm/{rev16.c => rev16_1.c}          |  0
 gcc/testsuite/gcc.target/arm/rev16_2.c             | 20 ++++++++++++++
 3 files changed, 40 insertions(+), 11 deletions(-)

diff --git a/gcc/config/arm/arm.md b/gcc/config/arm/arm.md
index 4a98f2d7b625..5816409f86f1 100644
--- a/gcc/config/arm/arm.md
+++ b/gcc/config/arm/arm.md
@@ -12578,7 +12578,10 @@
   "arm_arch6
    && aarch_rev16_shleft_mask_imm_p (operands[3], SImode)
    && aarch_rev16_shright_mask_imm_p (operands[2], SImode)"
-  "rev16\\t%0, %1"
+  "@
+   rev16\t%0, %1
+   rev16%?\t%0, %1
+   rev16%?\t%0, %1"
   [(set_attr "arch" "t1,t2,32")
    (set_attr "length" "2,2,4")
    (set_attr "type" "rev")]
@@ -12595,22 +12598,28 @@
   "arm_arch6
    && aarch_rev16_shleft_mask_imm_p (operands[3], SImode)
    && aarch_rev16_shright_mask_imm_p (operands[2], SImode)"
-  "rev16\\t%0, %1"
+  "@
+   rev16\t%0, %1
+   rev16%?\t%0, %1
+   rev16%?\t%0, %1"
   [(set_attr "arch" "t1,t2,32")
    (set_attr "length" "2,2,4")
    (set_attr "type" "rev")]
 )
 
-(define_expand "arm_rev16si2"
-  [(set (match_operand:SI 0 "s_register_operand")
-	(bswap:SI (match_operand:SI 1 "s_register_operand")))]
+;; Similar pattern to match (rotate (bswap) 16)
+(define_insn "arm_rev16si2"
+  [(set (match_operand:SI 0 "register_operand" "=l,l,r")
+        (rotate:SI (bswap:SI (match_operand:SI 1 "register_operand" "l,l,r"))
+                   (const_int 16)))]
   "arm_arch6"
-  {
-    rtx left = gen_int_mode (HOST_WIDE_INT_C (0xff00ff00ff00ff00), SImode);
-    rtx right = gen_int_mode (HOST_WIDE_INT_C (0xff00ff00ff00ff), SImode);
-    emit_insn (gen_arm_rev16si2_alt1 (operands[0], operands[1], right, left));
-    DONE;
-  }
+  "@
+   rev16\t%0, %1
+   rev16%?\t%0, %1
+   rev16%?\t%0, %1"
+  [(set_attr "arch" "t1,t2,32")
+   (set_attr "length" "2,2,4")
+   (set_attr "type" "rev")]
 )
 
 (define_expand "bswaphi2"
diff --git a/gcc/testsuite/gcc.target/arm/rev16.c b/gcc/testsuite/gcc.target/arm/rev16_1.c
similarity index 100%
rename from gcc/testsuite/gcc.target/arm/rev16.c
rename to gcc/testsuite/gcc.target/arm/rev16_1.c
diff --git a/gcc/testsuite/gcc.target/arm/rev16_2.c b/gcc/testsuite/gcc.target/arm/rev16_2.c
new file mode 100644
index 000000000000..c6553b38a000
--- /dev/null
+++ b/gcc/testsuite/gcc.target/arm/rev16_2.c
@@ -0,0 +1,20 @@
+/* { dg-options "-O2" } */
+/* { dg-do compile } */
+
+typedef unsigned int __u32;
+
+__u32
+__rev16_32_alt (__u32 x)
+{
+  return (((__u32)(x) & (__u32)0xff00ff00UL) >> 8)
+         | (((__u32)(x) & (__u32)0x00ff00ffUL) << 8);
+}
+
+__u32
+__rev16_32 (__u32 x)
+{
+  return (((__u32)(x) & (__u32)0x00ff00ffUL) << 8)
+         | (((__u32)(x) & (__u32)0xff00ff00UL) >> 8);
+}
+
+/* { dg-final { scan-assembler-times {rev16\tr[0-9]+, r[0-9]+} 2 } } */