Commit 1ea650bb75e009bb37b5bd4e896a90e2a86f8583 | zig

author	Jan Philipp Hafer <jan.hafer@rwth-aachen.de> 2021-09-03 01:12:48+02:00
committer	Andrew Kelley <andrew@ziglang.org> 2021-11-29 12:50:25-08:00
log	1ea650bb75e009bb37b5bd4e896a90e2a86f8583
tree	b23a47759b5c2f5c0f00a367227a56b03503c174
parent	d3426ce634a09ec289480510040b3decfbd38c39

compiler_rt: add popcountsi2, popcountdi2 and __popcountti2

- apply simpler approach than LLVM for __popcountdi2
  taken from The Art of Computer Programming and generalized
- rename popcountdi2.zig to popcount.zig
- test cases derived from popcountdi2_test.zig
- tests: compare naive approach 10_000 times with
  random numbers created from naive seed 42

    See #1290

7 files changed, 159 insertions(+), 39 deletions(-)

CMakeLists.txt
lib
- std
  - special
    compiler_rt.zig
    compiler_rt
    popcount.zig
    popcountdi2.zig
    popcountdi2_test.zig
    popcountsi2_test.zig
    popcountti2_test.zig

CMakeLists.txt+1-1

...	@@ -498,7 +498,7 @@ set(ZIG_STAGE2_SOURCES	...	@@ -498,7 +498,7 @@ set(ZIG_STAGE2_SOURCES
498	"${CMAKE_SOURCE_DIR}/lib/std/special/compiler_rt/multi3.zig"	498	"${CMAKE_SOURCE_DIR}/lib/std/special/compiler_rt/multi3.zig"
499	"${CMAKE_SOURCE_DIR}/lib/std/special/compiler_rt/negXf2.zig"	499	"${CMAKE_SOURCE_DIR}/lib/std/special/compiler_rt/negXf2.zig"
500	"${CMAKE_SOURCE_DIR}/lib/std/special/compiler_rt/os_version_check.zig"	500	"${CMAKE_SOURCE_DIR}/lib/std/special/compiler_rt/os_version_check.zig"
501	"${CMAKE_SOURCE_DIR}/lib/std/special/compiler_rt/popcountdi2.zig"	501	"${CMAKE_SOURCE_DIR}/lib/std/special/compiler_rt/popcount.zig"
502	"${CMAKE_SOURCE_DIR}/lib/std/special/compiler_rt/shift.zig"	502	"${CMAKE_SOURCE_DIR}/lib/std/special/compiler_rt/shift.zig"
503	"${CMAKE_SOURCE_DIR}/lib/std/special/compiler_rt/stack_probe.zig"	503	"${CMAKE_SOURCE_DIR}/lib/std/special/compiler_rt/stack_probe.zig"
504	"${CMAKE_SOURCE_DIR}/lib/std/special/compiler_rt/truncXfYf2.zig"	504	"${CMAKE_SOURCE_DIR}/lib/std/special/compiler_rt/truncXfYf2.zig"

lib/std/special/compiler_rt.zig+5-2

 @@ -177,7 +177,6 @@ comptime {
                     .linkage = linkage,
                 });
             },
             else => {},
         }
 @@ -334,8 +333,12 @@ comptime {
         const __udivmoddi4 = @import("compiler_rt/int.zig").__udivmoddi4;
         @export(__udivmoddi4, .{ .name = "__udivmoddi4", .linkage = linkage });
-        const __popcountdi2 = @import("compiler_rt/popcountdi2.zig").__popcountdi2;
+        const __popcountsi2 = @import("compiler_rt/popcount.zig").__popcountsi2;
+        @export(__popcountsi2, .{ .name = "__popcountsi2", .linkage = linkage });
+        const __popcountdi2 = @import("compiler_rt/popcount.zig").__popcountdi2;
         @export(__popcountdi2, .{ .name = "__popcountdi2", .linkage = linkage });
+        const __popcountti2 = @import("compiler_rt/popcount.zig").__popcountti2;
+        @export(__popcountti2, .{ .name = "__popcountti2", .linkage = linkage });
         if (is_darwin) {
             const __isPlatformVersionAtLeast = @import("compiler_rt/os_version_check.zig").__isPlatformVersionAtLeast;

lib/std/special/compiler_rt/popcount.zig created+66

...	@@ -0,0 +1,66 @@
1	const builtin = @import("builtin");
2	const std = @import("std");
3
4	// popcount - population count
5	// counts the number of 1 bits
6
7	// SWAR-Popcount: count bits of duos, aggregate to nibbles, and bytes inside
8	// x-bit register in parallel to sum up all bytes
9	// SWAR-Masks and factors can be defined as 2-adic fractions
10	// TAOCP: Combinational Algorithms, Bitwise Tricks And Techniques,
11	// subsubsection "Working with the rightmost bits" and "Sideways addition".
12	fn popcountXi2_generic(comptime T: type) fn (a: T) callconv(.C) i32 {
13	return struct {
14	fn f(a: T) callconv(.C) i32 {
15	@setRuntimeSafety(builtin.is_test);
16
17	var x = switch (@bitSizeOf(T)) {
18	32 => @bitCast(u32, a),
19	64 => @bitCast(u64, a),
20	128 => @bitCast(u128, a),
21	else => unreachable,
22	};
23	const k1 = switch (@bitSizeOf(T)) { // -1/3
24	32 => @as(u32, 0x55555555),
25	64 => @as(u64, 0x55555555_55555555),
26	128 => @as(u128, 0x55555555_55555555_55555555_55555555),
27	else => unreachable,
28	};
29	const k2 = switch (@bitSizeOf(T)) { // -1/5
30	32 => @as(u32, 0x33333333),
31	64 => @as(u64, 0x33333333_33333333),
32	128 => @as(u128, 0x33333333_33333333_33333333_33333333),
33	else => unreachable,
34	};
35	const k4 = switch (@bitSizeOf(T)) { // -1/17
36	32 => @as(u32, 0x0f0f0f0f),
37	64 => @as(u64, 0x0f0f0f0f_0f0f0f0f),
38	128 => @as(u128, 0x0f0f0f0f_0f0f0f0f_0f0f0f0f_0f0f0f0f),
39	else => unreachable,
40	};
41	const kf = switch (@bitSizeOf(T)) { // -1/255
42	32 => @as(u32, 0x01010101),
43	64 => @as(u64, 0x01010101_01010101),
44	128 => @as(u128, 0x01010101_01010101_01010101_01010101),
45	else => unreachable,
46	};
47	x = x - ((x >> 1) & k1); // aggregate duos
48	x = (x & k2) + ((x >> 2) & k2); // aggregate nibbles
49	x = (x + (x >> 4)) & k4; // aggregate bytes
50	x = (x *% kf) >> @bitSizeOf(T) - 8; // 8 most significant bits of x + (x<<8) + (x<<16) + ..
51	return @intCast(i32, x);
52	}
53	}.f;
54	}
55
56	pub const __popcountsi2 = popcountXi2_generic(i32);
57
58	pub const __popcountdi2 = popcountXi2_generic(i64);
59
60	pub const __popcountti2 = popcountXi2_generic(i128);
61
62	test {
63	_ = @import("popcountsi2_test.zig");
64	_ = @import("popcountdi2_test.zig");
65	_ = @import("popcountti2_test.zig");
66	}

lib/std/special/compiler_rt/popcountdi2.zig deleted-24

...	@@ -1,24 +0,0 @@
1	const builtin = @import("builtin");
2	const compiler_rt = @import("../compiler_rt.zig");
3
4	// ported from llvm compiler-rt 8.0.0rc3 95e1c294cb0415a377a7b1d6c7c7d4f89e1c04e4
5	pub fn __popcountdi2(a: i64) callconv(.C) i32 {
6	var x2 = @bitCast(u64, a);
7	x2 = x2 - ((x2 >> 1) & 0x5555555555555555);
8	// Every 2 bits holds the sum of every pair of bits (32)
9	x2 = ((x2 >> 2) & 0x3333333333333333) + (x2 & 0x3333333333333333);
10	// Every 4 bits holds the sum of every 4-set of bits (3 significant bits) (16)
11	x2 = (x2 + (x2 >> 4)) & 0x0F0F0F0F0F0F0F0F;
12	// Every 8 bits holds the sum of every 8-set of bits (4 significant bits) (8)
13	var x: u32 = @truncate(u32, x2 + (x2 >> 32));
14	// The lower 32 bits hold four 16 bit sums (5 significant bits).
15	// Upper 32 bits are garbage */
16	x = x + (x >> 16);
17	// The lower 16 bits hold two 32 bit sums (6 significant bits).
18	// Upper 16 bits are garbage */
19	return @bitCast(i32, (x + (x >> 8)) & 0x0000007F); // (7 significant bits)
20	}
21
22	test {
23	_ = @import("popcountdi2_test.zig");
24	}

lib/std/special/compiler_rt/popcountdi2_test.zig+19-12

...	@@ -1,27 +1,34 @@	...	@@ -1,27 +1,34 @@
1	const __popcountdi2 = @import("popcountdi2.zig").__popcountdi2;	1	const popcount = @import("popcount.zig");
2	const testing = @import("std").testing;	2	const testing = @import("std").testing;
3		3
4	fn naive_popcount(a_param: i64) i32 {	4	fn popcountdi2Naive(a: i64) i32 {
5	var a = a_param;	5	var x = a;
6	var r: i32 = 0;	6	var r: i32 = 0;
7	while (a != 0) : (a = @bitCast(i64, @bitCast(u64, a) >> 1)) {	7	while (x != 0) : (x = @bitCast(i64, @bitCast(u64, x) >> 1)) {
8	r += @intCast(i32, a & 1);	8	r += @intCast(i32, x & 1);
9	}	9	}
10	return r;	10	return r;
11	}	11	}
12		12
13	fn test__popcountdi2(a: i64) !void {	13	fn test__popcountdi2(a: i64) !void {
14	const x = __popcountdi2(a);	14	const x = popcount.__popcountdi2(a);
15	const expected = naive_popcount(a);	15	const expected = popcountdi2Naive(a);
16	try testing.expect(expected == x);	16	try testing.expectEqual(expected, x);
17	}	17	}
18		18
19	test "popcountdi2" {	19	test "popcountdi2" {
20	try test__popcountdi2(0);	20	try test__popcountdi2(0);
21	try test__popcountdi2(1);	21	try test__popcountdi2(1);
22	try test__popcountdi2(2);	22	try test__popcountdi2(2);
23	try test__popcountdi2(@bitCast(i64, @as(u64, 0xFFFFFFFFFFFFFFFD)));	23	try test__popcountdi2(@bitCast(i64, @as(u64, 0xffffffff_fffffffd)));
24	try test__popcountdi2(@bitCast(i64, @as(u64, 0xFFFFFFFFFFFFFFFE)));	24	try test__popcountdi2(@bitCast(i64, @as(u64, 0xffffffff_fffffffe)));
25	try test__popcountdi2(@bitCast(i64, @as(u64, 0xFFFFFFFFFFFFFFFF)));	25	try test__popcountdi2(@bitCast(i64, @as(u64, 0xffffffff_ffffffff)));
26	// TODO some fuzz testing	26
		27	const RndGen = @import("std").rand.DefaultPrng;
		28	var rnd = RndGen.init(42);
		29	var i: u32 = 0;
		30	while (i < 10_000) : (i += 1) {
		31	var rand_num = rnd.random().int(i64);
		32	try test__popcountdi2(rand_num);
		33	}
27	}	34	}

lib/std/special/compiler_rt/popcountsi2_test.zig created+34

...	@@ -0,0 +1,34 @@
1	const popcount = @import("popcount.zig");
2	const testing = @import("std").testing;
3
4	fn popcountsi2Naive(a: i32) i32 {
5	var x = a;
6	var r: i32 = 0;
7	while (x != 0) : (x = @bitCast(i32, @bitCast(u32, x) >> 1)) {
8	r += @intCast(i32, x & 1);
9	}
10	return r;
11	}
12
13	fn test__popcountsi2(a: i32) !void {
14	const x = popcount.__popcountsi2(a);
15	const expected = popcountsi2Naive(a);
16	try testing.expectEqual(expected, x);
17	}
18
19	test "popcountsi2" {
20	try test__popcountsi2(0);
21	try test__popcountsi2(1);
22	try test__popcountsi2(2);
23	try test__popcountsi2(@bitCast(i32, @as(u32, 0xfffffffd)));
24	try test__popcountsi2(@bitCast(i32, @as(u32, 0xfffffffe)));
25	try test__popcountsi2(@bitCast(i32, @as(u32, 0xffffffff)));
26
27	const RndGen = @import("std").rand.DefaultPrng;
28	var rnd = RndGen.init(42);
29	var i: u32 = 0;
30	while (i < 10_000) : (i += 1) {
31	var rand_num = rnd.random().int(i32);
32	try test__popcountsi2(rand_num);
33	}
34	}

lib/std/special/compiler_rt/popcountti2_test.zig created+34

...	@@ -0,0 +1,34 @@
1	const popcount = @import("popcount.zig");
2	const testing = @import("std").testing;
3
4	fn popcountti2Naive(a: i128) i32 {
5	var x = a;
6	var r: i32 = 0;
7	while (x != 0) : (x = @bitCast(i128, @bitCast(u128, x) >> 1)) {
8	r += @intCast(i32, x & 1);
9	}
10	return r;
11	}
12
13	fn test__popcountti2(a: i128) !void {
14	const x = popcount.__popcountti2(a);
15	const expected = popcountti2Naive(a);
16	try testing.expectEqual(expected, x);
17	}
18
19	test "popcountti2" {
20	try test__popcountti2(0);
21	try test__popcountti2(1);
22	try test__popcountti2(2);
23	try test__popcountti2(@bitCast(i128, @as(u128, 0xffffffff_ffffffff_ffffffff_fffffffd)));
24	try test__popcountti2(@bitCast(i128, @as(u128, 0xffffffff_ffffffff_ffffffff_fffffffe)));
25	try test__popcountti2(@bitCast(i128, @as(u128, 0xffffffff_ffffffff_ffffffff_ffffffff)));
26
27	const RndGen = @import("std").rand.DefaultPrng;
28	var rnd = RndGen.init(42);
29	var i: u32 = 0;
30	while (i < 10_000) : (i += 1) {
31	var rand_num = rnd.random().int(i128);
32	try test__popcountti2(rand_num);
33	}
34	}

compiler_rt: add __popcountsi2, __popcountdi2 and __popcountti2

compiler_rt: add popcountsi2, popcountdi2 and __popcountti2