[gcc r12-4473] bfin: Popcount-related improvements to machine description.

[gcc r12-4473] bfin: Popcount-related improvements to machine description.

[Roger Sayle]

https://gcc.gnu.org/g:fecda57e60488d15a180b8dde02cf7a4d978ebc7

commit r12-4473-gfecda57e60488d15a180b8dde02cf7a4d978ebc7
Author: Roger Sayle <roger@nextmovesoftware.com>
Date:   Mon Oct 18 11:56:56 2021 +0100

    bfin: Popcount-related improvements to machine description.
    
    Blackfin processors support a ONES instruction that implements a
    32-bit popcount returning a 16-bit result.  This instruction was
    previously described by GCC's bfin backend using an UNSPEC, which
    this patch changes to use a popcount:SI rtx thats capture its semantics,
    allowing it to evaluated and simplified at compile-time.  I've decided
    to keep the instruction name the same (avoiding any changes to the
    __builtin_bfin_ones machinery), but have provided popcountsi2 and
    popcounthi2 expanders so that the middle-end can use this instruction
    to implement __builtin_popcount (and __builtin_parity).
    
    The new testcase ones.c
    short foo ()
    {
      int t = 5;
      short r = __builtin_bfin_ones(t);
      return r;
    }
    
    previously generated:
    _foo:   nop;
            nop;
            R0 = 5 (X);
            R0.L = ONES R0;
            rts;
    
    with this patch, now generates:
    _foo:   nop;
            nop;
            nop;
            R0 = 2 (X);
            rts;
    
    The new testcase popcount.c
    int foo(int x)
    {
      return __builtin_popcount(x);
    }
    
    previously generated:
    _foo:   [--SP] = RETS;
            SP += -12;
            call ___popcountsi2;
            SP += 12;
            RETS = [SP++];
            rts;
    
    now generates:
    _foo:   nop;
            nop;
            R0.L = ONES R0;
            R0 = R0.L (Z);
            rts;
    
    And the new testcase parity.c
    int foo(int x)
    {
      return __builtin_parity(x);
    }
    
    previously generated:
    _foo:   [--SP] = RETS;
            SP += -12;
            call ___paritysi2;
            SP += 12;
            RETS = [SP++];
            rts;
    
    now generates:
    _foo:   nop;
            R1 = 1 (X);
            R0.L = ONES R0;
            R0 = R1 & R0;
            rts;
    
    2021-10-18  Roger Sayle  <roger@nextmovesoftware.com>
    
    gcc/ChangeLog
            * config/bfin/bfin.md (define_constants): Remove UNSPEC_ONES.
            (define_insn "ones"): Replace UNSPEC_ONES with a truncate of
            a popcount, allowing compile-time evaluation/simplification.
            (popcountsi2, popcounthi2): New expanders using a "ones" insn.
    
    gcc/testsuite/ChangeLog
            * gcc.target/bfin/ones.c: New test case.
            * gcc.target/bfin/parity.c: New test case.
            * gcc.target/bfin/popcount.c: New test case.

Diff:
---
 gcc/config/bfin/bfin.md                  | 27 +++++++++++++++++++++++----
 gcc/testsuite/gcc.target/bfin/ones.c     | 11 +++++++++++
 gcc/testsuite/gcc.target/bfin/parity.c   |  9 +++++++++
 gcc/testsuite/gcc.target/bfin/popcount.c |  9 +++++++++
 4 files changed, 52 insertions(+), 4 deletions(-)

diff --git a/gcc/config/bfin/bfin.md b/gcc/config/bfin/bfin.md
index 1ec0bbbd2d9..8b311f3ab11 100644
--- a/gcc/config/bfin/bfin.md
+++ b/gcc/config/bfin/bfin.md
@@ -138,8 +138,7 @@
    ;; Distinguish a 32-bit version of an insn from a 16-bit version.
    (UNSPEC_32BIT 11)
    (UNSPEC_NOP 12)
-   (UNSPEC_ONES 13)
-   (UNSPEC_ATOMIC 14)])
+   (UNSPEC_ATOMIC 13)])
 
 (define_constants
   [(UNSPEC_VOLATILE_CSYNC 1)
@@ -1398,12 +1397,32 @@
 
 (define_insn "ones"
   [(set (match_operand:HI 0 "register_operand" "=d")
-	(unspec:HI [(match_operand:SI 1 "register_operand" "d")]
-		UNSPEC_ONES))]
+	(truncate:HI
+	 (popcount:SI (match_operand:SI 1 "register_operand" "d"))))]
   ""
   "%h0 = ONES %1;"
   [(set_attr "type" "alu0")])
 
+(define_expand "popcountsi2"
+  [(set (match_dup 2)
+	(truncate:HI (popcount:SI (match_operand:SI 1 "register_operand" ""))))
+   (set (match_operand:SI 0 "register_operand")
+	(zero_extend:SI (match_dup 2)))]
+  ""
+{
+  operands[2] = gen_reg_rtx (HImode);
+})
+
+(define_expand "popcounthi2"
+  [(set (match_dup 2)
+	(zero_extend:SI (match_operand:HI 1 "register_operand" "")))
+   (set (match_operand:HI 0 "register_operand") 
+	(truncate:HI (popcount:SI (match_dup 2))))]
+  ""
+{
+  operands[2] = gen_reg_rtx (SImode);
+})
+
 (define_insn "smaxsi3"
   [(set (match_operand:SI 0 "register_operand" "=d")
 	(smax:SI (match_operand:SI 1 "register_operand" "d")
diff --git a/gcc/testsuite/gcc.target/bfin/ones.c b/gcc/testsuite/gcc.target/bfin/ones.c
new file mode 100644
index 00000000000..cdffe845c4d
--- /dev/null
+++ b/gcc/testsuite/gcc.target/bfin/ones.c
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+short foo ()
+{
+  int t = 5;
+  short r = __builtin_bfin_ones(t);
+  return r;
+}
+
+/* { dg-final { scan-assembler-not "ONES" } } */
diff --git a/gcc/testsuite/gcc.target/bfin/parity.c b/gcc/testsuite/gcc.target/bfin/parity.c
new file mode 100644
index 00000000000..6490b7fce02
--- /dev/null
+++ b/gcc/testsuite/gcc.target/bfin/parity.c
@@ -0,0 +1,9 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+int foo(int x)
+{
+  return __builtin_parity(x);
+}
+
+/* { dg-final { scan-assembler "ONES" } } */
diff --git a/gcc/testsuite/gcc.target/bfin/popcount.c b/gcc/testsuite/gcc.target/bfin/popcount.c
new file mode 100644
index 00000000000..51c19bee0c9
--- /dev/null
+++ b/gcc/testsuite/gcc.target/bfin/popcount.c
@@ -0,0 +1,9 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+int foo(int x)
+{
+  return __builtin_popcount(x);
+}
+
+/* { dg-final { scan-assembler "ONES" } } */