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.

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])
 

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);
+}

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;
+}