Commit e4c053f047

Jan Philipp Hafer <jan.hafer@rwth-aachen.de>
2021-12-01 11:27:40
compiler_rt: add __paritysi2, __paritydi2, __parityti2
- use Bit Twiddling Hacks: Compute parity in parallel - test cases derived from popcount.zig - tests: compare naive approach 10_000 times with random numbers created from naive seed 42 - compiler_rt.zig: sort by LLVM builtin order and add comments to improve structure See #1290
1 parent 02a1f83
lib/std/special/compiler_rt/parity.zig
@@ -0,0 +1,40 @@
+const std = @import("std");
+const builtin = @import("builtin");
+
+// parity - if number of bits set is even => 0, else => 1
+// - pariytXi2_generic for big and little endian
+
+fn parityXi2_generic(comptime T: type) fn (a: T) callconv(.C) i32 {
+    return struct {
+        fn f(a: T) callconv(.C) i32 {
+            @setRuntimeSafety(builtin.is_test);
+
+            var x = switch (@bitSizeOf(T)) {
+                32 => @bitCast(u32, a),
+                64 => @bitCast(u64, a),
+                128 => @bitCast(u128, a),
+                else => unreachable,
+            };
+            // Bit Twiddling Hacks: Compute parity in parallel
+            comptime var shift: u8 = @bitSizeOf(T) / 2;
+            inline while (shift > 2) {
+                x ^= x >> shift;
+                shift = shift >> 1;
+            }
+            x &= 0xf;
+            return (@intCast(u16, 0x6996) >> @intCast(u4, x)) & 1; // optimization for >>2 and >>1
+        }
+    }.f;
+}
+
+pub const __paritysi2 = parityXi2_generic(i32);
+
+pub const __paritydi2 = parityXi2_generic(i64);
+
+pub const __parityti2 = parityXi2_generic(i128);
+
+test {
+    _ = @import("paritysi2_test.zig");
+    _ = @import("paritydi2_test.zig");
+    _ = @import("parityti2_test.zig");
+}
lib/std/special/compiler_rt/paritydi2_test.zig
@@ -0,0 +1,35 @@
+const parity = @import("parity.zig");
+const testing = @import("std").testing;
+
+fn paritydi2Naive(a: i64) i32 {
+    var x = @bitCast(u64, a);
+    var has_parity: bool = false;
+    while (x > 0) {
+        has_parity = !has_parity;
+        x = x & (x - 1);
+    }
+    return @intCast(i32, @boolToInt(has_parity));
+}
+
+fn test__paritydi2(a: i64) !void {
+    var x = parity.__paritydi2(a);
+    var expected: i64 = paritydi2Naive(a);
+    try testing.expectEqual(expected, x);
+}
+
+test "paritydi2" {
+    try test__paritydi2(0);
+    try test__paritydi2(1);
+    try test__paritydi2(2);
+    try test__paritydi2(@bitCast(i64, @as(u64, 0xffffffff_fffffffd)));
+    try test__paritydi2(@bitCast(i64, @as(u64, 0xffffffff_fffffffe)));
+    try test__paritydi2(@bitCast(i64, @as(u64, 0xffffffff_ffffffff)));
+
+    const RndGen = @import("std").rand.DefaultPrng;
+    var rnd = RndGen.init(42);
+    var i: u32 = 0;
+    while (i < 10_000) : (i += 1) {
+        var rand_num = rnd.random().int(i64);
+        try test__paritydi2(rand_num);
+    }
+}
lib/std/special/compiler_rt/paritysi2_test.zig
@@ -0,0 +1,35 @@
+const parity = @import("parity.zig");
+const testing = @import("std").testing;
+
+fn paritysi2Naive(a: i32) i32 {
+    var x = @bitCast(u32, a);
+    var has_parity: bool = false;
+    while (x > 0) {
+        has_parity = !has_parity;
+        x = x & (x - 1);
+    }
+    return @intCast(i32, @boolToInt(has_parity));
+}
+
+fn test__paritysi2(a: i32) !void {
+    var x = parity.__paritysi2(a);
+    var expected: i32 = paritysi2Naive(a);
+    try testing.expectEqual(expected, x);
+}
+
+test "paritysi2" {
+    try test__paritysi2(0);
+    try test__paritysi2(1);
+    try test__paritysi2(2);
+    try test__paritysi2(@bitCast(i32, @as(u32, 0xfffffffd)));
+    try test__paritysi2(@bitCast(i32, @as(u32, 0xfffffffe)));
+    try test__paritysi2(@bitCast(i32, @as(u32, 0xffffffff)));
+
+    const RndGen = @import("std").rand.DefaultPrng;
+    var rnd = RndGen.init(42);
+    var i: u32 = 0;
+    while (i < 10_000) : (i += 1) {
+        var rand_num = rnd.random().int(i32);
+        try test__paritysi2(rand_num);
+    }
+}
lib/std/special/compiler_rt/parityti2_test.zig
@@ -0,0 +1,35 @@
+const parity = @import("parity.zig");
+const testing = @import("std").testing;
+
+fn parityti2Naive(a: i128) i32 {
+    var x = @bitCast(u128, a);
+    var has_parity: bool = false;
+    while (x > 0) {
+        has_parity = !has_parity;
+        x = x & (x - 1);
+    }
+    return @intCast(i32, @boolToInt(has_parity));
+}
+
+fn test__parityti2(a: i128) !void {
+    var x = parity.__parityti2(a);
+    var expected: i128 = parityti2Naive(a);
+    try testing.expectEqual(expected, x);
+}
+
+test "parityti2" {
+    try test__parityti2(0);
+    try test__parityti2(1);
+    try test__parityti2(2);
+    try test__parityti2(@bitCast(i128, @as(u128, 0xffffffff_ffffffff_ffffffff_fffffffd)));
+    try test__parityti2(@bitCast(i128, @as(u128, 0xffffffff_ffffffff_ffffffff_fffffffe)));
+    try test__parityti2(@bitCast(i128, @as(u128, 0xffffffff_ffffffff_ffffffff_ffffffff)));
+
+    const RndGen = @import("std").rand.DefaultPrng;
+    var rnd = RndGen.init(42);
+    var i: u32 = 0;
+    while (i < 10_000) : (i += 1) {
+        var rand_num = rnd.random().int(i128);
+        try test__parityti2(rand_num);
+    }
+}
lib/std/special/compiler_rt.zig
@@ -76,10 +76,11 @@ comptime {
 
         @export(__extendhfsf2, .{ .name = "__gnu_h2f_ieee", .linkage = linkage });
 
-        const __muloti4 = @import("compiler_rt/muloti4.zig").__muloti4;
-        @export(__muloti4, .{ .name = "__muloti4", .linkage = linkage });
+        // Integral arithmetic which returns if overflow
         const __mulodi4 = @import("compiler_rt/mulodi4.zig").__mulodi4;
         @export(__mulodi4, .{ .name = "__mulodi4", .linkage = linkage });
+        const __muloti4 = @import("compiler_rt/muloti4.zig").__muloti4;
+        @export(__muloti4, .{ .name = "__muloti4", .linkage = linkage });
     }
 
     if (builtin.os.tag == .windows) {
@@ -217,6 +218,7 @@ comptime {
         const __divtf3 = @import("compiler_rt/divtf3.zig").__divtf3;
         @export(__divtf3, .{ .name = "__divtf3", .linkage = linkage });
 
+        // Integral bit manipulation
         const __ashldi3 = @import("compiler_rt/shift.zig").__ashldi3;
         @export(__ashldi3, .{ .name = "__ashldi3", .linkage = linkage });
         const __ashlti3 = @import("compiler_rt/shift.zig").__ashlti3;
@@ -230,6 +232,33 @@ comptime {
         const __lshrti3 = @import("compiler_rt/shift.zig").__lshrti3;
         @export(__lshrti3, .{ .name = "__lshrti3", .linkage = linkage });
 
+        const __clzsi2 = @import("compiler_rt/count0bits.zig").__clzsi2;
+        @export(__clzsi2, .{ .name = "__clzsi2", .linkage = linkage });
+        const __clzdi2 = @import("compiler_rt/count0bits.zig").__clzdi2;
+        @export(__clzdi2, .{ .name = "__clzdi2", .linkage = linkage });
+        const __clzti2 = @import("compiler_rt/count0bits.zig").__clzti2;
+        @export(__clzti2, .{ .name = "__clzti2", .linkage = linkage });
+        const __ctzsi2 = @import("compiler_rt/count0bits.zig").__ctzsi2;
+        @export(__ctzsi2, .{ .name = "__ctzsi2", .linkage = linkage });
+        const __ctzdi2 = @import("compiler_rt/count0bits.zig").__ctzdi2;
+        @export(__ctzdi2, .{ .name = "__ctzdi2", .linkage = linkage });
+        const __ctzti2 = @import("compiler_rt/count0bits.zig").__ctzti2;
+        @export(__ctzti2, .{ .name = "__ctzti2", .linkage = linkage });
+
+        const __paritysi2 = @import("compiler_rt/parity.zig").__paritysi2;
+        @export(__paritysi2, .{ .name = "__paritysi2", .linkage = linkage });
+        const __paritydi2 = @import("compiler_rt/parity.zig").__paritydi2;
+        @export(__paritydi2, .{ .name = "__paritydi2", .linkage = linkage });
+        const __parityti2 = @import("compiler_rt/parity.zig").__parityti2;
+        @export(__parityti2, .{ .name = "__parityti2", .linkage = linkage });
+        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 });
+
+        // Integral / floating point conversion (part 1/2)
         const __floatsidf = @import("compiler_rt/floatsiXf.zig").__floatsidf;
         @export(__floatsidf, .{ .name = "__floatsidf", .linkage = linkage });
         const __floatsisf = @import("compiler_rt/floatsiXf.zig").__floatsisf;
@@ -291,6 +320,7 @@ comptime {
         const __extendsfdf2 = @import("compiler_rt/extendXfYf2.zig").__extendsfdf2;
         @export(__extendsfdf2, .{ .name = "__extendsfdf2", .linkage = linkage });
 
+        // Integral / floating point conversion (part 2/2)
         const __fixunssfsi = @import("compiler_rt/fixunssfsi.zig").__fixunssfsi;
         @export(__fixunssfsi, .{ .name = "__fixunssfsi", .linkage = linkage });
         const __fixunssfdi = @import("compiler_rt/fixunssfdi.zig").__fixunssfdi;
@@ -333,18 +363,13 @@ comptime {
 
         const __udivmoddi4 = @import("compiler_rt/int.zig").__udivmoddi4;
         @export(__udivmoddi4, .{ .name = "__udivmoddi4", .linkage = linkage });
-        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;
             @export(__isPlatformVersionAtLeast, .{ .name = "__isPlatformVersionAtLeast", .linkage = linkage });
         }
 
+        // Integral arithmetic
         const __mulsi3 = @import("compiler_rt/int.zig").__mulsi3;
         @export(__mulsi3, .{ .name = "__mulsi3", .linkage = linkage });
         const __muldi3 = @import("compiler_rt/muldi3.zig").__muldi3;
@@ -372,24 +397,26 @@ comptime {
         const __udivmodsi4 = @import("compiler_rt/int.zig").__udivmodsi4;
         @export(__udivmodsi4, .{ .name = "__udivmodsi4", .linkage = linkage });
 
+        // missing: Integral arithmetic with trapping overflow
+
+        // missing: Integral arithmetic which returns if overflow
+
+        // missing: Integral comparison
+        // (a <  b) => 0
+        // (a == b) => 1
+        // (a >  b) => 2
+
+        // missing: Floating point raised to integer power
+
+        // missing: Complex arithmetic
+        // (a + ib) * (c + id)
+        // (a + ib) / (c + id)
+
         const __negsf2 = @import("compiler_rt/negXf2.zig").__negsf2;
         @export(__negsf2, .{ .name = "__negsf2", .linkage = linkage });
         const __negdf2 = @import("compiler_rt/negXf2.zig").__negdf2;
         @export(__negdf2, .{ .name = "__negdf2", .linkage = linkage });
 
-        const __clzsi2 = @import("compiler_rt/count0bits.zig").__clzsi2;
-        @export(__clzsi2, .{ .name = "__clzsi2", .linkage = linkage });
-        const __clzdi2 = @import("compiler_rt/count0bits.zig").__clzdi2;
-        @export(__clzdi2, .{ .name = "__clzdi2", .linkage = linkage });
-        const __clzti2 = @import("compiler_rt/count0bits.zig").__clzti2;
-        @export(__clzti2, .{ .name = "__clzti2", .linkage = linkage });
-        const __ctzsi2 = @import("compiler_rt/count0bits.zig").__ctzsi2;
-        @export(__ctzsi2, .{ .name = "__ctzsi2", .linkage = linkage });
-        const __ctzdi2 = @import("compiler_rt/count0bits.zig").__ctzdi2;
-        @export(__ctzdi2, .{ .name = "__ctzdi2", .linkage = linkage });
-        const __ctzti2 = @import("compiler_rt/count0bits.zig").__ctzti2;
-        @export(__ctzti2, .{ .name = "__ctzti2", .linkage = linkage });
-
         if (builtin.link_libc and os_tag == .openbsd) {
             const __emutls_get_address = @import("compiler_rt/emutls.zig").__emutls_get_address;
             @export(__emutls_get_address, .{ .name = "__emutls_get_address", .linkage = linkage });
CMakeLists.txt
@@ -498,6 +498,7 @@ set(ZIG_STAGE2_SOURCES
     "${CMAKE_SOURCE_DIR}/lib/std/special/compiler_rt/multi3.zig"
     "${CMAKE_SOURCE_DIR}/lib/std/special/compiler_rt/negXf2.zig"
     "${CMAKE_SOURCE_DIR}/lib/std/special/compiler_rt/os_version_check.zig"
+    "${CMAKE_SOURCE_DIR}/lib/std/special/compiler_rt/parity.zig"
     "${CMAKE_SOURCE_DIR}/lib/std/special/compiler_rt/popcount.zig"
     "${CMAKE_SOURCE_DIR}/lib/std/special/compiler_rt/shift.zig"
     "${CMAKE_SOURCE_DIR}/lib/std/special/compiler_rt/stack_probe.zig"