Support asm x86 popcnt (#2314)

* Support asm x86 popcnt

test/unit/asm/popcnt.c3

@@ -0,0 +1,25 @@
+module test::inline_asm::popcnt @if (env::X86_64);
+
+fn void popcntw() @test
+{
+	short src   = 0xF0;
+	short count = 0;
+	asm { popcntw count, src; }
+	assert(count == 4, "inline asm: popcntw failed");
+}
+
+fn void popcntl() @test
+{
+	int src   = 0xF0F0;
+	int count = 0;
+	asm { popcntl count, src; }
+	assert(count == 8, "inline asm: popcntl failed");
+}
+
+fn void popcntq() @test
+{
+	long src   = 0xF0F0_F0F0;
+	long count = 0;
+	asm { popcntq count, src; }
+	assert(count == 16, "inline asm: popcntq failed");
+}