Commit d0277a3d17

Daniele Cocca <daniele.cocca@gmail.com>
2022-03-13 01:43:51
CBE: implement popCount, byteSwap, bitReverse for ints <= 128 bits
This folds the airCountZeroes() code from 226fcd7c709ec664c5d883042cf7beb3026f66cb back into airBuiltinCall(), since most of these builtins happen to require the same arguments and can be unified under a common function signature.
1 parent 87744a7
Changed files (6)
src/codegen/c.zig
@@ -1711,8 +1711,8 @@ fn genBody(f: *Function, body: []const Air.Inst.Index) error{ AnalysisFail, OutO
             .memcpy           => try airMemcpy(f, inst),
             .set_union_tag    => try airSetUnionTag(f, inst),
             .get_union_tag    => try airGetUnionTag(f, inst),
-            .clz              => try airCountZeroes(f, inst, "clz"),
-            .ctz              => try airCountZeroes(f, inst, "ctz"),
+            .clz              => try airBuiltinCall(f, inst, "clz"),
+            .ctz              => try airBuiltinCall(f, inst, "ctz"),
             .popcount         => try airBuiltinCall(f, inst, "popcount"),
             .byte_swap        => try airBuiltinCall(f, inst, "byte_swap"),
             .bit_reverse      => try airBuiltinCall(f, inst, "bit_reverse"),
@@ -3352,23 +3352,6 @@ fn airPtrToInt(f: *Function, inst: Air.Inst.Index) !CValue {
 fn airBuiltinCall(f: *Function, inst: Air.Inst.Index, fn_name: [*:0]const u8) !CValue {
     if (f.liveness.isUnused(inst)) return CValue.none;
 
-    const inst_ty = f.air.typeOfIndex(inst);
-    const local = try f.allocLocal(inst_ty, .Const);
-    const ty_op = f.air.instructions.items(.data)[inst].ty_op;
-    const writer = f.object.writer();
-    const operand = try f.resolveInst(ty_op.operand);
-
-    // TODO implement the function in zig.h and call it here
-
-    try writer.print(" = {s}(", .{fn_name});
-    try f.writeCValue(writer, operand);
-    try writer.writeAll(");\n");
-    return local;
-}
-
-fn airCountZeroes(f: *Function, inst: Air.Inst.Index, fn_name: [*:0]const u8) !CValue {
-    if (f.liveness.isUnused(inst)) return CValue.none;
-
     const inst_ty = f.air.typeOfIndex(inst);
     const local = try f.allocLocal(inst_ty, .Const);
     const operand = f.air.instructions.items(.data)[inst].ty_op.operand;
@@ -3376,13 +3359,17 @@ fn airCountZeroes(f: *Function, inst: Air.Inst.Index, fn_name: [*:0]const u8) !C
     const target = f.object.dg.module.getTarget();
     const writer = f.object.writer();
 
-    const zig_bits = operand_ty.intInfo(target).bits;
-    _ = toCIntBits(zig_bits) orelse
+    const int_info = operand_ty.intInfo(target);
+    _ = toCIntBits(int_info.bits) orelse
         return f.fail("TODO: C backend: implement integer types larger than 128 bits", .{});
+    const signed_type = switch (int_info.signedness) {
+        .signed => "true",
+        .unsigned => "false",
+    };
 
     try writer.print(" = zig_{s}(", .{fn_name});
     try f.writeCValue(writer, try f.resolveInst(operand));
-    try writer.print(", {d});\n", .{zig_bits});
+    try writer.print(", {d}, {s});\n", .{ int_info.bits, signed_type });
     return local;
 }
 
src/link/C/zig.h
@@ -502,8 +502,20 @@ zig_shl_sat_s(int,        int, ((sizeof(int     )) * CHAR_BIT - 1))
 zig_shl_sat_s(long,      long, ((sizeof(long    )) * CHAR_BIT - 1))
 
 #define zig_bitsizeof(T) (CHAR_BIT * sizeof(T))
+#define zig_bit_mask(T, bit_width) \
+    ((bit_width) == 128 \
+     ? ((T)(((uint128_t) 0xffffffffffffffff) << 64 | \
+             (uint128_t) 0xffffffffffffffff)) \
+     : (((T)1 << (T)(bit_width)) - 1))
+
+static inline uint128_t zig_sign_extend(uint128_t value, uint128_t zig_type_bit_width) {
+    const uint128_t m = (uint128_t)1 << (zig_type_bit_width - 1);
+    return (value ^ m) - m;
+}
+
+static inline int zig_clz(unsigned long long value, uint8_t zig_type_bit_width, bool signed_type) {
+    (void)signed_type; // unused
 
-static inline int zig_clz(uint64_t value, uint8_t zig_type_bit_width) {
     if (value == 0) return zig_type_bit_width;
     if (zig_type_bit_width <= zig_bitsizeof(unsigned int))
         return (__builtin_clz(value) - zig_bitsizeof(unsigned int) + zig_type_bit_width);
@@ -512,9 +524,89 @@ static inline int zig_clz(uint64_t value, uint8_t zig_type_bit_width) {
     return (__builtin_clzll(value) - zig_bitsizeof(unsigned long long) + zig_type_bit_width);
 }
 
-static inline int zig_ctz(uint64_t value, uint8_t zig_type_bit_width) {
+static inline int zig_ctz(unsigned long long value, uint8_t zig_type_bit_width, bool signed_type) {
+    (void)signed_type; // unused
+
     if (value == 0) return zig_type_bit_width;
     if (zig_type_bit_width <= zig_bitsizeof(unsigned int)) return __builtin_ctz(value);
     if (zig_type_bit_width <= zig_bitsizeof(unsigned long)) return __builtin_ctzl(value);
     return __builtin_ctzll(value);
 }
+
+static inline int zig_popcount(unsigned long long value, uint8_t zig_type_bit_width, bool signed_type) {
+    (void)signed_type; // unused
+
+    const unsigned long long mask = zig_bit_mask(unsigned long long, zig_type_bit_width);
+    if (zig_type_bit_width <= zig_bitsizeof(unsigned int))
+        return __builtin_popcount(value & mask);
+    if (zig_type_bit_width <= zig_bitsizeof(unsigned long))
+        return __builtin_popcountl(value & mask);
+    return __builtin_popcountll(value & mask);
+}
+
+static inline uint128_t zig_byte_swap(uint128_t value, uint8_t zig_type_bit_width, bool signed_type) {
+    if (zig_type_bit_width <= 8)  return value;
+    if (zig_type_bit_width <= 16) return __builtin_bswap16(value);
+    if (zig_type_bit_width <= 32) {
+        const uint32_t swapped = __builtin_bswap32(value) >> (32 - zig_type_bit_width);
+        return (signed_type ? zig_sign_extend(swapped, zig_type_bit_width) : swapped);
+    }
+    if (zig_type_bit_width <= 64) {
+        const uint64_t swapped = __builtin_bswap64(value) >> (64 - zig_type_bit_width);
+        return (signed_type ? zig_sign_extend(swapped, zig_type_bit_width) : swapped);
+    }
+    const uint128_t mask = zig_bit_mask(uint128_t, zig_type_bit_width);
+    const uint128_t hi = __builtin_bswap64((uint64_t)(value >> 64));
+    const uint128_t lo = __builtin_bswap64((uint64_t)value);
+    const uint128_t swapped = (((lo << 64 | hi) >> (128 - zig_type_bit_width))) & mask;
+    return (signed_type ? zig_sign_extend(swapped, zig_type_bit_width) : swapped);
+}
+
+static inline uint128_t zig_bit_reverse(uint128_t value, uint8_t zig_type_bit_width, bool signed_type) {
+    static const uint128_t reverse_lut[256] = {
+        0x00, 0x80, 0x40, 0xc0, 0x20, 0xa0, 0x60, 0xe0, 0x10, 0x90, 0x50, 0xd0,
+        0x30, 0xb0, 0x70, 0xf0, 0x08, 0x88, 0x48, 0xc8, 0x28, 0xa8, 0x68, 0xe8,
+        0x18, 0x98, 0x58, 0xd8, 0x38, 0xb8, 0x78, 0xf8, 0x04, 0x84, 0x44, 0xc4,
+        0x24, 0xa4, 0x64, 0xe4, 0x14, 0x94, 0x54, 0xd4, 0x34, 0xb4, 0x74, 0xf4,
+        0x0c, 0x8c, 0x4c, 0xcc, 0x2c, 0xac, 0x6c, 0xec, 0x1c, 0x9c, 0x5c, 0xdc,
+        0x3c, 0xbc, 0x7c, 0xfc, 0x02, 0x82, 0x42, 0xc2, 0x22, 0xa2, 0x62, 0xe2,
+        0x12, 0x92, 0x52, 0xd2, 0x32, 0xb2, 0x72, 0xf2, 0x0a, 0x8a, 0x4a, 0xca,
+        0x2a, 0xaa, 0x6a, 0xea, 0x1a, 0x9a, 0x5a, 0xda, 0x3a, 0xba, 0x7a, 0xfa,
+        0x06, 0x86, 0x46, 0xc6, 0x26, 0xa6, 0x66, 0xe6, 0x16, 0x96, 0x56, 0xd6,
+        0x36, 0xb6, 0x76, 0xf6, 0x0e, 0x8e, 0x4e, 0xce, 0x2e, 0xae, 0x6e, 0xee,
+        0x1e, 0x9e, 0x5e, 0xde, 0x3e, 0xbe, 0x7e, 0xfe, 0x01, 0x81, 0x41, 0xc1,
+        0x21, 0xa1, 0x61, 0xe1, 0x11, 0x91, 0x51, 0xd1, 0x31, 0xb1, 0x71, 0xf1,
+        0x09, 0x89, 0x49, 0xc9, 0x29, 0xa9, 0x69, 0xe9, 0x19, 0x99, 0x59, 0xd9,
+        0x39, 0xb9, 0x79, 0xf9, 0x05, 0x85, 0x45, 0xc5, 0x25, 0xa5, 0x65, 0xe5,
+        0x15, 0x95, 0x55, 0xd5, 0x35, 0xb5, 0x75, 0xf5, 0x0d, 0x8d, 0x4d, 0xcd,
+        0x2d, 0xad, 0x6d, 0xed, 0x1d, 0x9d, 0x5d, 0xdd, 0x3d, 0xbd, 0x7d, 0xfd,
+        0x03, 0x83, 0x43, 0xc3, 0x23, 0xa3, 0x63, 0xe3, 0x13, 0x93, 0x53, 0xd3,
+        0x33, 0xb3, 0x73, 0xf3, 0x0b, 0x8b, 0x4b, 0xcb, 0x2b, 0xab, 0x6b, 0xeb,
+        0x1b, 0x9b, 0x5b, 0xdb, 0x3b, 0xbb, 0x7b, 0xfb, 0x07, 0x87, 0x47, 0xc7,
+        0x27, 0xa7, 0x67, 0xe7, 0x17, 0x97, 0x57, 0xd7, 0x37, 0xb7, 0x77, 0xf7,
+        0x0f, 0x8f, 0x4f, 0xcf, 0x2f, 0xaf, 0x6f, 0xef, 0x1f, 0x9f, 0x5f, 0xdf,
+        0x3f, 0xbf, 0x7f, 0xff
+    };
+    const uint128_t mask = zig_bit_mask(uint128_t, zig_type_bit_width);
+    const uint128_t swapped = zig_byte_swap(value, zig_type_bit_width, signed_type);
+    const uint128_t reversed = (
+        (reverse_lut[(swapped >> 0x78) & 0xff] << 0x78) |
+        (reverse_lut[(swapped >> 0x70) & 0xff] << 0x70) |
+        (reverse_lut[(swapped >> 0x68) & 0xff] << 0x68) |
+        (reverse_lut[(swapped >> 0x60) & 0xff] << 0x60) |
+        (reverse_lut[(swapped >> 0x58) & 0xff] << 0x58) |
+        (reverse_lut[(swapped >> 0x50) & 0xff] << 0x50) |
+        (reverse_lut[(swapped >> 0x48) & 0xff] << 0x48) |
+        (reverse_lut[(swapped >> 0x40) & 0xff] << 0x40) |
+        (reverse_lut[(swapped >> 0x38) & 0xff] << 0x38) |
+        (reverse_lut[(swapped >> 0x30) & 0xff] << 0x30) |
+        (reverse_lut[(swapped >> 0x28) & 0xff] << 0x28) |
+        (reverse_lut[(swapped >> 0x20) & 0xff] << 0x20) |
+        (reverse_lut[(swapped >> 0x18) & 0xff] << 0x18) |
+        (reverse_lut[(swapped >> 0x10) & 0xff] << 0x10) |
+        (reverse_lut[(swapped >> 0x08) & 0xff] << 0x08) |
+        (reverse_lut[(swapped >> 0x00) & 0xff] << 0x00));
+    const uint128_t result =
+        (reversed >> (zig_type_bit_width < 8 ? 8 - zig_type_bit_width : 0)) & mask;
+    return (signed_type ? zig_sign_extend(result, zig_type_bit_width) : result);
+}
test/behavior/bitreverse.zig
@@ -5,7 +5,6 @@ const minInt = std.math.minInt;
 
 test "@bitReverse large exotic integer" {
     if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest;
-    if (builtin.zig_backend == .stage2_c) return error.SkipZigTest;
     // Currently failing on stage1 for big-endian targets
     if (builtin.zig_backend == .stage1) return error.SkipZigTest;
 
@@ -14,7 +13,6 @@ test "@bitReverse large exotic integer" {
 
 test "@bitReverse" {
     if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest;
-    if (builtin.zig_backend == .stage2_c) return error.SkipZigTest;
     if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest;
     if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest;
     if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
test/behavior/byteswap.zig
@@ -4,7 +4,6 @@ const expect = std.testing.expect;
 
 test "@byteSwap integers" {
     if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest;
-    if (builtin.zig_backend == .stage2_c) return error.SkipZigTest;
     if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest;
     if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest;
     if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
test/behavior/popcount.zig
@@ -1,3 +1,4 @@
+const builtin = @import("builtin");
 const std = @import("std");
 const expect = std.testing.expect;
 const expectEqual = std.testing.expectEqual;
@@ -45,6 +46,8 @@ fn testPopCountIntegers() !void {
 }
 
 test "@popCount vectors" {
+    if (builtin.zig_backend == .stage2_c) return error.SkipZigTest; // TODO
+
     comptime try testPopCountVectors();
     try testPopCountVectors();
 }
test/behavior.zig
@@ -139,6 +139,7 @@ test {
         _ = @import("behavior/eval.zig");
         _ = @import("behavior/export_self_referential_type_info.zig");
         _ = @import("behavior/int128.zig");
+        _ = @import("behavior/popcount.zig");
         _ = @import("behavior/translate_c_macros.zig");
         _ = @import("behavior/union_with_members.zig");
 
@@ -147,7 +148,6 @@ test {
             _ = @import("behavior/atomics.zig");
             _ = @import("behavior/export.zig");
             _ = @import("behavior/maximum_minimum.zig");
-            _ = @import("behavior/popcount.zig");
             _ = @import("behavior/saturating_arithmetic.zig");
             _ = @import("behavior/widening.zig");
             _ = @import("behavior/bugs/2114.zig");