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util: add boolean lookup table helpers
Many instruction sets (Intel, Apple, NVIDIA) implement bitwise operations with a single general instruction that takes a lookup table in sum-of-products (minterms) form. Working with these tables manually is a bit gnarly, and multiple backends need to do this. This adds common code for representing such lookup tables with 2- or 3-sources, with a rich set of helpers for building, inspecting, and manipulating the LUTs. Eventually, we may want to introduce a nir_op_bitop3 instruction to NIR to build common code for fusing boolean expression trees into lookup tables. That NIR pass will presumably use the helpers here. NAK already has this abstraction internally (in Rust). Possibly NAK will be able to drop (or cut down) that code once we handle this in NIR. Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@intel.com> Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/37200>
This commit is contained in:
Alyssa Rosenzweig
Marge Bot
parent
86a5dd10ac
commit
95badb6b1d
3 changed files with 379 additions and 0 deletions
271
src/util/lut.c
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271
src/util/lut.c
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/*
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* Copyright 2020 Intel Corporation
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* SPDX-License-Identifier: MIT
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*/
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/*
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* This table was generated by an offline tool in the following manner:
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* for each function value, we generated a tree of all expressions that evaluate
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* to that function. Then we normalized, simplified, and pruned the tree to take
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* the first minimal size expression.
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*
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* https://github.com/intel/intel-graphics-compiler/blob/eb7d24be2244c6e2225d7b33eefcd6ec62b6f80e/visa/iga/IGALibrary/api/iga_bxml_enums.cpp
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*/
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const char *util_lut3_to_str[256] = {
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[0x00] = "zeros",
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[0x01] = "~a & ~b & ~c",
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[0x02] = "a & ~b & ~c",
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[0x03] = "~b & ~c",
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[0x04] = "~a & b & ~c",
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[0x05] = "~a & ~c",
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[0x06] = "(a ^ b) & ~c",
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[0x07] = "(~a | ~b) & ~c",
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[0x08] = "a & b & ~c",
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[0x09] = "(a ^ ~b) & ~c",
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[0x0A] = "a & ~c",
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[0x0B] = "(a | ~b) & ~c",
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[0x0C] = "b & ~c",
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[0x0D] = "(~a | b) & ~c",
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[0x0E] = "(a | b) & ~c",
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[0x0F] = "~c",
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[0x10] = "~a & ~b & c",
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[0x11] = "~a & ~b",
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[0x12] = "(a ^ c) & ~b",
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[0x13] = "(~a | ~c) & ~b",
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[0x14] = "~a & (b ^ c)",
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[0x15] = "~a & (~b | ~c)",
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[0x16] = "a ^ (a & b | b ^ c)",
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[0x17] = "~a & ~b | (~a | ~b) & ~c",
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[0x18] = "(a ^ c) & (b ^ c)",
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[0x19] = "a ^ (a & c | ~b)",
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[0x1A] = "a ^ (a | ~b) & c",
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[0x1B] = "a & ~c | ~a & ~b",
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[0x1C] = "(a & c | b) ^ c",
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[0x1D] = "~a & ~b | b & ~c",
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[0x1E] = "(a | b) ^ c",
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[0x1F] = "~a & ~b | ~c",
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[0x20] = "a & ~b & c",
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[0x21] = "(a ^ ~c) & ~b",
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[0x22] = "a & ~b",
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[0x23] = "(a | ~c) & ~b",
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[0x24] = "(a ^ b) & (b ^ c)",
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[0x25] = "a ^ (a & b | ~c)",
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[0x26] = "a ^ (a | ~c) & b",
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[0x27] = "a & ~b | ~a & ~c",
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[0x28] = "a & (b ^ c)",
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[0x29] = "a ^ (a | ~b) & (b ^ ~c)",
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[0x2A] = "a & (~b | ~c)",
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[0x2B] = "a & ~b | (a | ~b) & ~c",
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[0x2C] = "(~a & c | b) ^ c",
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[0x2D] = "(~a | b) ^ c",
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[0x2E] = "a & ~b | b & ~c",
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[0x2F] = "a & ~b | ~c",
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[0x30] = "~b & c",
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[0x31] = "(~a | c) & ~b",
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[0x32] = "(a | c) & ~b",
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[0x33] = "~b",
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[0x34] = "(a & b | c) ^ b",
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[0x35] = "~a & ~c | ~b & c",
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[0x36] = "(a | c) ^ b",
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[0x37] = "~a & ~c | ~b",
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[0x38] = "(~a & b | c) ^ b",
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[0x39] = "(~a | c) ^ b",
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[0x3A] = "a & ~c | ~b & c",
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[0x3B] = "a & ~c | ~b",
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[0x3C] = "b ^ c",
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[0x3D] = "~a & ~b | b ^ c",
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[0x3E] = "a & ~b | b ^ c",
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[0x3F] = "~b | ~c",
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[0x40] = "~a & b & c",
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[0x41] = "~a & (b ^ ~c)",
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[0x42] = "(a ^ b) & (b ^ ~c)",
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[0x43] = "(a & b | ~c) ^ b",
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[0x44] = "~a & b",
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[0x45] = "~a & (b | ~c)",
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[0x46] = "a ^ (a & c | b)",
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[0x47] = "~a & b | ~b & ~c",
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[0x48] = "(a ^ c) & b",
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[0x49] = "a ^ (a & c | b ^ ~c)",
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[0x4A] = "a ^ (a | b) & c",
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[0x4B] = "(a | ~b) ^ c",
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[0x4C] = "(~a | ~c) & b",
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[0x4D] = "~a & b | (~a | b) & ~c",
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[0x4E] = "a & ~c | ~a & b",
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[0x4F] = "~a & b | ~c",
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[0x50] = "~a & c",
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[0x51] = "~a & (~b | c)",
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[0x52] = "a ^ (a & b | c)",
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[0x53] = "~a & c | ~b & ~c",
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[0x54] = "~a & (b | c)",
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[0x55] = "~a",
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[0x56] = "a ^ (b | c)",
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[0x57] = "~a | ~b & ~c",
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[0x58] = "a ^ (a & ~b | c)",
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[0x59] = "a ^ (~b | c)",
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[0x5A] = "a ^ c",
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[0x5B] = "a ^ c | ~a & ~b",
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[0x5C] = "~a & c | b & ~c",
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[0x5D] = "~a | b & ~c",
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[0x5E] = "a ^ c | b & ~c",
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[0x5F] = "~a | ~c",
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[0x60] = "(a ^ b) & c",
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[0x61] = "a ^ (a & b | b ^ ~c)",
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[0x62] = "a ^ (a | c) & b",
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[0x63] = "(a | ~c) ^ b",
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[0x64] = "a ^ (a & ~c | b)",
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[0x65] = "a ^ (b | ~c)",
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[0x66] = "a ^ b",
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[0x67] = "a ^ b | ~a & ~c",
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[0x68] = "a ^ (a | b) & (b ^ ~c)",
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[0x69] = "a ^ b ^ ~c",
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[0x6A] = "a ^ b & c",
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[0x6B] = "a ^ b & c | ~b & ~c",
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[0x6C] = "(~a | ~c) ^ ~b",
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[0x6D] = "a ^ (b | ~c) | b & ~c",
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[0x6E] = "a ^ b | a & ~c",
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[0x6F] = "a ^ b | ~c",
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[0x70] = "(~a | ~b) & c",
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[0x71] = "~a & c | (~a | c) & ~b",
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[0x72] = "a & ~b | ~a & c",
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[0x73] = "~a & c | ~b",
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[0x74] = "~a & b | ~b & c",
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[0x75] = "~a | ~b & c",
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[0x76] = "a ^ b | ~a & c",
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[0x77] = "~a | ~b",
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[0x78] = "(~a | ~b) ^ ~c",
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[0x79] = "a ^ (~b | c) | ~b & c",
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[0x7A] = "a ^ c | a & ~b",
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[0x7B] = "a ^ c | ~b",
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[0x7C] = "~a & b | b ^ c",
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[0x7D] = "~a | b ^ c",
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[0x7E] = "a ^ b | b ^ c",
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[0x7F] = "~a | ~b | ~c",
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[0x80] = "a & b & c",
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[0x81] = "(a ^ ~b) & (b ^ ~c)",
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[0x82] = "a & (b ^ ~c)",
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[0x83] = "(~a & b | ~c) ^ b",
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[0x84] = "(a ^ ~c) & b",
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[0x85] = "a ^ (a & ~b | ~c)",
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[0x86] = "a ^ (a | b) & (b ^ c)",
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[0x87] = "(~a | ~b) ^ c",
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[0x88] = "a & b",
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[0x89] = "a ^ (a | ~c) & ~b",
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[0x8A] = "a & (b | ~c)",
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[0x8B] = "a & b | ~b & ~c",
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[0x8C] = "(a | ~c) & b",
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[0x8D] = "a & b | ~a & ~c",
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[0x8E] = "a & b | (a | b) & ~c",
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[0x8F] = "a & b | ~c",
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[0x90] = "(a ^ ~b) & c",
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[0x91] = "a ^ (a & ~c | ~b)",
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[0x92] = "a ^ (a | c) & (b ^ c)",
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[0x93] = "(~a | ~c) ^ b",
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[0x94] = "a ^ (a & ~b | b ^ c)",
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[0x95] = "a ^ (~b | ~c)",
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[0x96] = "a ^ b ^ c",
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[0x97] = "a ^ (~b | ~c) | ~b & ~c",
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[0x98] = "a ^ (a | c) & ~b",
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[0x99] = "a ^ ~b",
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[0x9A] = "a ^ ~b & c",
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[0x9B] = "a ^ ~b | a & ~c",
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[0x9C] = "(a | ~c) ^ ~b",
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[0x9D] = "a ^ ~b | b & ~c",
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[0x9E] = "a ^ ~b & c | b & ~c",
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[0x9F] = "a ^ ~b | ~c",
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[0xA0] = "a & c",
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[0xA1] = "a ^ (a | ~b) & ~c",
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[0xA2] = "a & (~b | c)",
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[0xA3] = "a & c | ~b & ~c",
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[0xA4] = "a ^ (a | b) & ~c",
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[0xA5] = "a ^ ~c",
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[0xA6] = "a ^ b & ~c",
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[0xA7] = "a ^ ~c | a & ~b",
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[0xA8] = "a & (b | c)",
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[0xA9] = "a ^ ~b & ~c",
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[0xAA] = "a",
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[0xAB] = "a | ~b & ~c",
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[0xAC] = "a & c | b & ~c",
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[0xAD] = "a ^ ~c | a & b",
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[0xAE] = "a | b & ~c",
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[0xAF] = "a | ~c",
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[0xB0] = "(a | ~b) & c",
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[0xB1] = "a & c | ~a & ~b",
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[0xB2] = "a & c | (a | c) & ~b",
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[0xB3] = "a & c | ~b",
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[0xB4] = "(a | ~b) ^ ~c",
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[0xB5] = "a ^ ~c | ~a & ~b",
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[0xB6] = "a ^ b & ~c | ~b & c",
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[0xB7] = "a ^ ~c | ~b",
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[0xB8] = "a & b | ~b & c",
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[0xB9] = "a ^ ~b | a & c",
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[0xBA] = "a | ~b & c",
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[0xBB] = "a | ~b",
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[0xBC] = "a & b | b ^ c",
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[0xBD] = "a ^ ~b | b ^ c",
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[0xBE] = "a | b ^ c",
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[0xBF] = "a | ~b | ~c",
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[0xC0] = "b & c",
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[0xC1] = "(a & ~b | c) ^ ~b",
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[0xC2] = "(~a & ~b | c) ^ ~b",
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[0xC3] = "b ^ ~c",
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[0xC4] = "(~a | c) & b",
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[0xC5] = "~a & ~c | b & c",
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[0xC6] = "(~a | c) ^ ~b",
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[0xC7] = "~a & b | b ^ ~c",
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[0xC8] = "(a | c) & b",
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[0xC9] = "(a | c) ^ ~b",
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[0xCA] = "a & ~c | b & c",
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[0xCB] = "a & b | b ^ ~c",
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[0xCC] = "b",
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[0xCD] = "~a & ~c | b",
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[0xCE] = "a & ~c | b",
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[0xCF] = "b | ~c",
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[0xD0] = "(~a | b) & c",
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[0xD1] = "~a & ~b | b & c",
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[0xD2] = "(~a | b) ^ ~c",
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[0xD3] = "~a & c | b ^ ~c",
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[0xD4] = "~a & b | (~a | b) & c",
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[0xD5] = "~a | b & c",
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[0xD6] = "a ^ (b | c) | b & c",
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[0xD7] = "~a | b ^ ~c",
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[0xD8] = "a & b | ~a & c",
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[0xD9] = "a ^ ~b | b & c",
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[0xDA] = "a ^ c | a & b",
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[0xDB] = "a ^ c | b ^ ~c",
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[0xDC] = "~a & c | b",
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[0xDD] = "~a | b",
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[0xDE] = "a ^ c | b",
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[0xDF] = "~a | b | ~c",
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[0xE0] = "(a | b) & c",
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[0xE1] = "(a | b) ^ ~c",
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[0xE2] = "a & ~b | b & c",
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[0xE3] = "a & c | b ^ ~c",
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[0xE4] = "a & c | ~a & b",
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[0xE5] = "a ^ ~c | b & c",
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[0xE6] = "a ^ b | a & c",
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[0xE7] = "a ^ b | b ^ ~c",
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[0xE8] = "a & b | (a | b) & c",
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[0xE9] = "a ^ ~b & ~c | b & c",
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[0xEA] = "a | b & c",
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[0xEB] = "a | b ^ ~c",
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[0xEC] = "a & c | b",
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[0xED] = "a ^ ~c | b",
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[0xEE] = "a | b",
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[0xEF] = "a | b | ~c",
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[0xF0] = "c",
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[0xF1] = "~a & ~b | c",
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[0xF2] = "a & ~b | c",
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[0xF3] = "~b | c",
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[0xF4] = "~a & b | c",
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[0xF5] = "~a | c",
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[0xF6] = "a ^ b | c",
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[0xF7] = "~a | ~b | c",
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[0xF8] = "a & b | c",
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[0xF9] = "a ^ ~b | c",
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[0xFA] = "a | c",
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[0xFB] = "a | ~b | c",
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[0xFC] = "b | c",
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[0xFD] = "~a | b | c",
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[0xFE] = "a | b | c",
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[0xFF] = "ones",
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};
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107
src/util/lut.h
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107
src/util/lut.h
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/*
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* Copyright 2025 Intel Corporation
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* SPDX-License-Identifier: MIT
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*/
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#pragma once
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#include <assert.h>
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#include <stdint.h>
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#include "util/macros.h"
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/*
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* Represents a boolean lookup table in sum-of-minterms form. These are
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* natural encodings, matching the Intel BFN and Apple BITOP instructions.
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*/
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typedef uint8_t util_lut2;
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typedef uint8_t util_lut3;
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#if !defined(_MSC_VER)
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/*
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* Build a lookup table from a boolean expression. Bitwise operations are
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* supported: &, |, ^, and ~. Note ~ must be used, not !.
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*
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* The implementation uses a GNU statement-expression with the appropriate
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* masks, such that the AND of all three masks (with arbitrary complements)
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* equals the single bit for the corresponding min-term. This matches how Intel
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* describes BFN in the bspec, but it obscures the meaning.
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*
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* Casting to uint8_t masks the out-of-bounds bits in ~a & ~b & ~c.
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*
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* Example: UTIL_LUT3((a & b) | (~a & c))
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*/
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#define UTIL_LUT3(expr_involving_a_b_c) \
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({ \
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UNUSED const uint8_t a = 0xAA, b = 0xCC, c = 0xF0; \
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(util_lut3)(expr_involving_a_b_c); \
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})
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#define UTIL_LUT2(expr_involving_a_b) \
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(util_lut2) UTIL_LUT3((expr_involving_a_b) & ~c)
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/*
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* Return a lookup table with source s inverted. We exchange the minterms for
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* "source a is true" and "source a is false".
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*/
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static inline util_lut3
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util_lut3_invert_source(util_lut3 l, unsigned s)
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{
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uint8_t masks[] = {UTIL_LUT3(a), UTIL_LUT3(b), UTIL_LUT3(c)};
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assert(s < ARRAY_SIZE(masks));
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uint8_t mask = masks[s];
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uint8_t shift = __builtin_ctz(mask);
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uint8_t true_bits = l & mask;
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uint8_t false_bits = l & ~mask;
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return (false_bits << shift) | (true_bits >> shift);
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}
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static inline util_lut2
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util_lut2_invert_source(util_lut2 l, unsigned s)
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{
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return (util_lut2)(util_lut3_invert_source((util_lut3)l, s) & 0xf);
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}
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#endif
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/*
|
||||
* Helpers to invert a LUT. This is easy: invert all the min-terms.
|
||||
*/
|
||||
static inline util_lut2
|
||||
util_lut2_invert(util_lut2 l)
|
||||
{
|
||||
return l ^ 0xf;
|
||||
}
|
||||
|
||||
static inline util_lut3
|
||||
util_lut3_invert(util_lut3 l)
|
||||
{
|
||||
return l ^ 0xff;
|
||||
}
|
||||
|
||||
/*
|
||||
* Return a lookup table equivalent to the input but with sources a & b swapped.
|
||||
* To implement, we swap the corresponding minterms.
|
||||
*/
|
||||
static inline util_lut2
|
||||
util_lut2_swap_sources(util_lut2 l)
|
||||
{
|
||||
return util_bit_swap(l, 1, 2);
|
||||
}
|
||||
|
||||
static inline util_lut3
|
||||
util_lut3_swap_sources(util_lut3 l, unsigned a, unsigned b)
|
||||
{
|
||||
if (a == 0 && b == 1) {
|
||||
return util_bit_swap(util_bit_swap(l, 1, 2), 5, 6);
|
||||
} else if (a == 0 && b == 2) {
|
||||
return util_bit_swap(util_bit_swap(l, 1, 4), 3, 6);
|
||||
} else if (a == 1 && b == 2) {
|
||||
return util_bit_swap(util_bit_swap(l, 2, 4), 3, 5);
|
||||
}
|
||||
|
||||
UNREACHABLE("invalid source selection");
|
||||
}
|
||||
|
||||
|
||||
/* Finding minimal string forms of LUTs is tricky, so we precompute. */
|
||||
extern const char *util_lut3_to_str[256];
|
||||
|
|
@ -64,6 +64,7 @@ files_mesa_util = files(
|
|||
'u_idalloc.h',
|
||||
'list.h',
|
||||
'log.c',
|
||||
'lut.c',
|
||||
'macros.h',
|
||||
'memstream.c',
|
||||
'memstream.h',
|
||||
|
|
|
|||
Loading…
Add table
Reference in a new issue