[gcc r14-6072] LoongArch: Accelerate optimization of scalar signed/unsigned popcount.

[LuluCheng]

https://gcc.gnu.org/g:a68ae55883113c10320b164738eebadaf08df5b0

commit r14-6072-ga68ae55883113c10320b164738eebadaf08df5b0
Author: Li Wei <liwei@loongson.cn>
Date:   Tue Nov 28 15:38:37 2023 +0800

    LoongArch: Accelerate optimization of scalar signed/unsigned popcount.
    
    In LoongArch, the vector popcount has corresponding instructions, while
    the scalar does not. Currently, the scalar popcount is calculated
    through a loop, and the value of a non-power of two needs to be iterated
    several times, so the vector popcount instruction is considered for
    optimization.
    
    gcc/ChangeLog:
    
            * config/loongarch/loongarch.md (v2di): Used to simplify the
            following templates.
            (popcount<mode>2): New.
    
    gcc/testsuite/ChangeLog:
    
            * gcc.target/loongarch/popcnt.c: New test.
            * gcc.target/loongarch/popcount.c: New test.

Diff:
---
 gcc/config/loongarch/loongarch.md             | 27 ++++++++++++++++--
 gcc/testsuite/gcc.target/loongarch/popcnt.c   | 41 +++++++++++++++++++++++++++
 gcc/testsuite/gcc.target/loongarch/popcount.c | 17 +++++++++++
 3 files changed, 83 insertions(+), 2 deletions(-)

diff --git a/gcc/config/loongarch/loongarch.md b/gcc/config/loongarch/loongarch.md
index 1e019815451..7a101dd64b7 100644
--- a/gcc/config/loongarch/loongarch.md
+++ b/gcc/config/loongarch/loongarch.md
@@ -1512,7 +1512,30 @@
    (set_attr "cnv_mode"	"D2S")
    (set_attr "mode" "SF")])
 
-

+;; In vector registers, popcount can be implemented directly through
+;; the vector instruction [X]VPCNT.  For GP registers, we can implement
+;; it through the following method.  Compared with loop implementation
+;; of popcount, the following method has better performance.
+
+;; This attribute used for get connection of scalar mode and corresponding
+;; vector mode.
+(define_mode_attr cntmap [(SI "v4si") (DI "v2di")])
+
+(define_expand "popcount<mode>2"
+  [(set (match_operand:GPR 0 "register_operand")
+	(popcount:GPR (match_operand:GPR 1 "register_operand")))]
+  "ISA_HAS_LSX"
+{
+  rtx in = operands[1];
+  rtx out = operands[0];
+  rtx vreg = <MODE>mode == SImode ? gen_reg_rtx (V4SImode) :
+				    gen_reg_rtx (V2DImode);
+  emit_insn (gen_lsx_vinsgr2vr_<size> (vreg, in, vreg, GEN_INT (1)));
+  emit_insn (gen_popcount<cntmap>2 (vreg, vreg));
+  emit_insn (gen_lsx_vpickve2gr_<size> (out, vreg, GEN_INT (0)));
+  DONE;
+})
+
 ;;
 ;;  ....................
 ;;
@@ -3879,7 +3902,7 @@
 		   (any_extend:SI (match_dup 3)))])]
   "")
 
-

+
 
 (define_mode_iterator QHSD [QI HI SI DI])
 
diff --git a/gcc/testsuite/gcc.target/loongarch/popcnt.c b/gcc/testsuite/gcc.target/loongarch/popcnt.c
new file mode 100644
index 00000000000..a10fca42092
--- /dev/null
+++ b/gcc/testsuite/gcc.target/loongarch/popcnt.c
@@ -0,0 +1,41 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -mlsx" } */
+/* { dg-final { scan-assembler-not {popcount} } } */
+/* { dg-final { scan-assembler-times "vpcnt.d" 2 { target { loongarch64*-*-* } } } } */
+/* { dg-final { scan-assembler-times "vpcnt.w" 4 { target { loongarch64*-*-* } } } } */
+
+int
+foo (int x)
+{
+  return __builtin_popcount (x);
+}
+
+long
+foo1 (long x)
+{
+  return __builtin_popcountl (x);
+}
+
+long long
+foo2 (long long x)
+{
+  return __builtin_popcountll (x);
+}
+
+int
+foo3 (int *p)
+{
+  return __builtin_popcount (*p);
+}
+
+unsigned
+foo4 (int x)
+{
+  return __builtin_popcount (x);
+}
+
+unsigned long
+foo5 (int x)
+{
+  return __builtin_popcount (x);
+}
diff --git a/gcc/testsuite/gcc.target/loongarch/popcount.c b/gcc/testsuite/gcc.target/loongarch/popcount.c
new file mode 100644
index 00000000000..390ff067617
--- /dev/null
+++ b/gcc/testsuite/gcc.target/loongarch/popcount.c
@@ -0,0 +1,17 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -mlsx -fdump-tree-optimized" } */
+/* { dg-final { scan-tree-dump-times "__builtin_popcount|\\.POPCOUNT" 1 "optimized" } } */
+
+int
+PopCount (long b)
+{
+  int c = 0;
+
+  while (b)
+    {
+      b &= b - 1;
+      c++;
+    }
+
+  return c;
+}