1 //===---- llvm/Support/Discriminator.h -- Discriminator Utils ---*- C++ -*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file defines the constants and utility functions for discriminators.
10 //
11 //===----------------------------------------------------------------------===//
12
13 #ifndef LLVM_SUPPORT_DISCRIMINATOR_H
14 #define LLVM_SUPPORT_DISCRIMINATOR_H
15
16 #include "llvm/Support/Error.h"
17 #include <assert.h>
18
19 // Utility functions for encoding / decoding discriminators.
20 /// With a given unsigned int \p U, use up to 13 bits to represent it.
21 /// old_bit 1~5 --> new_bit 1~5
22 /// old_bit 6~12 --> new_bit 7~13
23 /// new_bit_6 is 0 if higher bits (7~13) are all 0
getPrefixEncodingFromUnsigned(unsigned U)24 static inline unsigned getPrefixEncodingFromUnsigned(unsigned U) {
25 U &= 0xfff;
26 return U > 0x1f ? (((U & 0xfe0) << 1) | (U & 0x1f) | 0x20) : U;
27 }
28
29 /// Reverse transformation as getPrefixEncodingFromUnsigned.
getUnsignedFromPrefixEncoding(unsigned U)30 static inline unsigned getUnsignedFromPrefixEncoding(unsigned U) {
31 if (U & 1)
32 return 0;
33 U >>= 1;
34 return (U & 0x20) ? (((U >> 1) & 0xfe0) | (U & 0x1f)) : (U & 0x1f);
35 }
36
37 /// Returns the next component stored in discriminator.
getNextComponentInDiscriminator(unsigned D)38 static inline unsigned getNextComponentInDiscriminator(unsigned D) {
39 if ((D & 1) == 0)
40 return D >> ((D & 0x40) ? 14 : 7);
41 else
42 return D >> 1;
43 }
44
encodeComponent(unsigned C)45 static inline unsigned encodeComponent(unsigned C) {
46 return (C == 0) ? 1U : (getPrefixEncodingFromUnsigned(C) << 1);
47 }
48
encodingBits(unsigned C)49 static inline unsigned encodingBits(unsigned C) {
50 return (C == 0) ? 1 : (C > 0x1f ? 14 : 7);
51 }
52
53 // Some constants used in FS Discriminators.
54 //
55 namespace llvm {
56 namespace sampleprof {
57 enum FSDiscriminatorPass {
58 Base = 0,
59 Pass0 = 0,
60 Pass1 = 1,
61 Pass2 = 2,
62 Pass3 = 3,
63 Pass4 = 4,
64 PassLast = 4,
65 };
66 } // namespace sampleprof
67
68 // The number of bits reserved for the base discrimininator. The base
69 // discriminaitor starts from bit 0.
70 static const unsigned BaseDiscriminatorBitWidth = 8;
71
72 // The number of bits reserved for each FS discriminator pass.
73 static const unsigned FSDiscriminatorBitWidth = 6;
74
75 // Return the number of FS passes, excluding the pass adding the base
76 // discriminators.
77 // The number of passes for FS discriminators. Note that the total
78 // number of discriminaitor bits, i.e.
79 // BaseDiscriminatorBitWidth
80 // + FSDiscriminatorBitWidth * getNumFSPasses()
81 // needs to fit in an unsigned int type.
getNumFSPasses()82 static inline unsigned getNumFSPasses() {
83 return static_cast<unsigned>(sampleprof::FSDiscriminatorPass::PassLast);
84 }
85
86 // Return the ending bit for FSPass P.
getFSPassBitEnd(sampleprof::FSDiscriminatorPass P)87 static inline unsigned getFSPassBitEnd(sampleprof::FSDiscriminatorPass P) {
88 unsigned I = static_cast<unsigned>(P);
89 assert(I <= getNumFSPasses() && "Invalid FS discriminator pass number.");
90 return BaseDiscriminatorBitWidth + I * FSDiscriminatorBitWidth - 1;
91 }
92
93 // Return the begining bit for FSPass P.
getFSPassBitBegin(sampleprof::FSDiscriminatorPass P)94 static inline unsigned getFSPassBitBegin(sampleprof::FSDiscriminatorPass P) {
95 if (P == sampleprof::FSDiscriminatorPass::Base)
96 return 0;
97 unsigned I = static_cast<unsigned>(P);
98 assert(I <= getNumFSPasses() && "Invalid FS discriminator pass number.");
99 return getFSPassBitEnd(static_cast<sampleprof::FSDiscriminatorPass>(I - 1)) +
100 1;
101 }
102
103 // Return the beginning bit for the last FSPass.
getLastFSPassBitBegin()104 static inline int getLastFSPassBitBegin() {
105 return getFSPassBitBegin(
106 static_cast<sampleprof::FSDiscriminatorPass>(getNumFSPasses()));
107 }
108
109 // Return the ending bit for the last FSPass.
getLastFSPassBitEnd()110 static inline unsigned getLastFSPassBitEnd() {
111 return getFSPassBitEnd(
112 static_cast<sampleprof::FSDiscriminatorPass>(getNumFSPasses()));
113 }
114
115 // Return the beginning bit for the base (first) FSPass.
getBaseFSBitBegin()116 static inline unsigned getBaseFSBitBegin() { return 0; }
117
118 // Return the ending bit for the base (first) FSPass.
getBaseFSBitEnd()119 static inline unsigned getBaseFSBitEnd() {
120 return BaseDiscriminatorBitWidth - 1;
121 }
122
123 // Set bits in range of [0 .. n] to 1. Used in FS Discriminators.
getN1Bits(int N)124 static inline unsigned getN1Bits(int N) {
125 // Work around the g++ bug that folding "(1U << (N + 1)) - 1" to 0.
126 if (N == 31)
127 return 0xFFFFFFFF;
128 assert((N < 32) && "N is invalid");
129 return (1U << (N + 1)) - 1;
130 }
131
132 } // namespace llvm
133
134 #endif /* LLVM_SUPPORT_DISCRIMINATOR_H */
135