cranelift_codegen/
settings.rs

1//! Shared settings module.
2//!
3//! This module defines data structures to access the settings defined in the meta language.
4//!
5//! Each settings group is translated to a `Flags` struct either in this module or in its
6//! ISA-specific `settings` module. The struct provides individual getter methods for all of the
7//! settings as well as computed predicate flags.
8//!
9//! The `Flags` struct is immutable once it has been created. A `Builder` instance is used to
10//! create it.
11//!
12//! # Example
13//! ```
14//! use cranelift_codegen::settings::{self, Configurable};
15//!
16//! let mut b = settings::builder();
17//! b.set("opt_level", "speed_and_size");
18//!
19//! let f = settings::Flags::new(b);
20//! assert_eq!(f.opt_level(), settings::OptLevel::SpeedAndSize);
21//! ```
22
23use crate::constant_hash::{probe, simple_hash};
24use crate::isa::TargetIsa;
25use alloc::boxed::Box;
26use alloc::string::{String, ToString};
27use core::fmt;
28use core::str;
29
30/// A string-based configurator for settings groups.
31///
32/// The `Configurable` protocol allows settings to be modified by name before a finished `Flags`
33/// struct is created.
34pub trait Configurable {
35    /// Set the string value of any setting by name.
36    ///
37    /// This can set any type of setting whether it is numeric, boolean, or enumerated.
38    fn set(&mut self, name: &str, value: &str) -> SetResult<()>;
39
40    /// Enable a boolean setting or apply a preset.
41    ///
42    /// If the identified setting isn't a boolean or a preset, a `BadType` error is returned.
43    fn enable(&mut self, name: &str) -> SetResult<()>;
44}
45
46/// Represents the kind of setting.
47#[derive(Clone, Copy, Debug, Eq, PartialEq)]
48pub enum SettingKind {
49    /// The setting is an enumeration.
50    Enum,
51    /// The setting is a number.
52    Num,
53    /// The setting is a boolean.
54    Bool,
55    /// The setting is a preset.
56    Preset,
57}
58
59/// Represents an available builder setting.
60///
61/// This is used for iterating settings in a builder.
62#[derive(Clone, Copy, Debug)]
63pub struct Setting {
64    /// The name of the setting.
65    pub name: &'static str,
66    /// The description of the setting.
67    pub description: &'static str,
68    /// The kind of the setting.
69    pub kind: SettingKind,
70    /// The supported values of the setting (for enum values).
71    pub values: Option<&'static [&'static str]>,
72}
73
74/// Represents a setting value.
75///
76/// This is used for iterating values in `Flags`.
77pub struct Value {
78    /// The name of the setting associated with this value.
79    pub name: &'static str,
80    pub(crate) detail: detail::Detail,
81    pub(crate) values: Option<&'static [&'static str]>,
82    pub(crate) value: u8,
83}
84
85impl Value {
86    /// Gets the kind of setting.
87    pub fn kind(&self) -> SettingKind {
88        match &self.detail {
89            detail::Detail::Enum { .. } => SettingKind::Enum,
90            detail::Detail::Num => SettingKind::Num,
91            detail::Detail::Bool { .. } => SettingKind::Bool,
92            detail::Detail::Preset => unreachable!(),
93        }
94    }
95
96    /// Gets the enum value if the value is from an enum setting.
97    pub fn as_enum(&self) -> Option<&'static str> {
98        self.values.map(|v| v[self.value as usize])
99    }
100
101    /// Gets the numerical value if the value is from a num setting.
102    pub fn as_num(&self) -> Option<u8> {
103        match &self.detail {
104            detail::Detail::Num => Some(self.value),
105            _ => None,
106        }
107    }
108
109    /// Gets the boolean value if the value is from a boolean setting.
110    pub fn as_bool(&self) -> Option<bool> {
111        match &self.detail {
112            detail::Detail::Bool { bit } => Some(self.value & (1 << bit) != 0),
113            _ => None,
114        }
115    }
116
117    /// Builds a string from the current value
118    pub fn value_string(&self) -> String {
119        match self.kind() {
120            SettingKind::Enum => self.as_enum().map(|b| b.to_string()),
121            SettingKind::Num => self.as_num().map(|b| b.to_string()),
122            SettingKind::Bool => self.as_bool().map(|b| b.to_string()),
123            SettingKind::Preset => unreachable!(),
124        }
125        .unwrap()
126    }
127}
128
129impl fmt::Display for Value {
130    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
131        if let Some(enum_variant) = self.as_enum() {
132            write!(f, "{}={}", self.name, enum_variant)
133        } else if let Some(num) = self.as_num() {
134            write!(f, "{}={}", self.name, num)
135        } else if let Some(b) = self.as_bool() {
136            if b {
137                write!(f, "{}=1", self.name)
138            } else {
139                write!(f, "{}=0", self.name)
140            }
141        } else {
142            unreachable!()
143        }
144    }
145}
146
147/// Collect settings values based on a template.
148#[derive(Clone, Hash)]
149pub struct Builder {
150    template: &'static detail::Template,
151    bytes: Box<[u8]>,
152}
153
154impl Builder {
155    /// Create a new builder with defaults and names from the given template.
156    pub fn new(tmpl: &'static detail::Template) -> Self {
157        Self {
158            template: tmpl,
159            bytes: tmpl.defaults.into(),
160        }
161    }
162
163    /// Extract contents of builder once everything is configured.
164    pub fn state_for(&self, name: &str) -> &[u8] {
165        assert_eq!(name, self.template.name);
166        &self.bytes
167    }
168
169    /// Iterates the available settings in the builder.
170    pub fn iter(&self) -> impl Iterator<Item = Setting> + use<> {
171        let template = self.template;
172
173        template.descriptors.iter().map(move |d| {
174            let (kind, values) = match d.detail {
175                detail::Detail::Enum { last, enumerators } => {
176                    let values = template.enums(last, enumerators);
177                    (SettingKind::Enum, Some(values))
178                }
179                detail::Detail::Num => (SettingKind::Num, None),
180                detail::Detail::Bool { .. } => (SettingKind::Bool, None),
181                detail::Detail::Preset => (SettingKind::Preset, None),
182            };
183
184            Setting {
185                name: d.name,
186                description: d.description,
187                kind,
188                values,
189            }
190        })
191    }
192
193    /// Set the value of a single bit.
194    fn set_bit(&mut self, offset: usize, bit: u8, value: bool) {
195        let byte = &mut self.bytes[offset];
196        let mask = 1 << bit;
197        if value {
198            *byte |= mask;
199        } else {
200            *byte &= !mask;
201        }
202    }
203
204    /// Apply a preset. The argument is a slice of (mask, value) bytes.
205    fn apply_preset(&mut self, values: &[(u8, u8)]) {
206        for (byte, &(mask, value)) in self.bytes.iter_mut().zip(values) {
207            *byte = (*byte & !mask) | value;
208        }
209    }
210
211    /// Look up a descriptor by name.
212    fn lookup(&self, name: &str) -> SetResult<(usize, detail::Detail)> {
213        match probe(self.template, name, simple_hash(name)) {
214            Err(_) => Err(SetError::BadName(name.to_string())),
215            Ok(entry) => {
216                let d = &self.template.descriptors[self.template.hash_table[entry] as usize];
217                Ok((d.offset as usize, d.detail))
218            }
219        }
220    }
221}
222
223fn parse_bool_value(value: &str) -> SetResult<bool> {
224    match value {
225        "true" | "on" | "yes" | "1" => Ok(true),
226        "false" | "off" | "no" | "0" => Ok(false),
227        _ => Err(SetError::BadValue("bool".to_string())),
228    }
229}
230
231fn parse_enum_value(value: &str, choices: &[&str]) -> SetResult<u8> {
232    match choices.iter().position(|&tag| tag == value) {
233        Some(idx) => Ok(idx as u8),
234        None => Err(SetError::BadValue(format!(
235            "any among {}",
236            choices.join(", ")
237        ))),
238    }
239}
240
241impl Configurable for Builder {
242    fn enable(&mut self, name: &str) -> SetResult<()> {
243        use self::detail::Detail;
244        let (offset, detail) = self.lookup(name)?;
245        match detail {
246            Detail::Bool { bit } => {
247                self.set_bit(offset, bit, true);
248                Ok(())
249            }
250            Detail::Preset => {
251                self.apply_preset(&self.template.presets[offset..]);
252                Ok(())
253            }
254            _ => Err(SetError::BadType),
255        }
256    }
257
258    fn set(&mut self, name: &str, value: &str) -> SetResult<()> {
259        use self::detail::Detail;
260        let (offset, detail) = self.lookup(name)?;
261        match detail {
262            Detail::Bool { bit } => {
263                self.set_bit(offset, bit, parse_bool_value(value)?);
264            }
265            Detail::Num => {
266                self.bytes[offset] = value
267                    .parse()
268                    .map_err(|_| SetError::BadValue("number".to_string()))?;
269            }
270            Detail::Enum { last, enumerators } => {
271                self.bytes[offset] =
272                    parse_enum_value(value, self.template.enums(last, enumerators))?;
273            }
274            Detail::Preset => return Err(SetError::BadName(name.to_string())),
275        }
276        Ok(())
277    }
278}
279
280/// An error produced when changing a setting.
281#[derive(Debug, PartialEq, Eq)]
282pub enum SetError {
283    /// No setting by this name exists.
284    BadName(String),
285
286    /// Type mismatch for setting (e.g., setting an enum setting as a bool).
287    BadType,
288
289    /// This is not a valid value for this setting.
290    BadValue(String),
291}
292
293impl std::error::Error for SetError {}
294
295impl fmt::Display for SetError {
296    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
297        match self {
298            SetError::BadName(name) => write!(f, "No existing setting named '{name}'"),
299            SetError::BadType => {
300                write!(f, "Trying to set a setting with the wrong type")
301            }
302            SetError::BadValue(value) => {
303                write!(f, "Unexpected value for a setting, expected {value}")
304            }
305        }
306    }
307}
308
309/// A result returned when changing a setting.
310pub type SetResult<T> = Result<T, SetError>;
311
312/// A reference to just the boolean predicates of a settings object.
313///
314/// The settings objects themselves are generated and appear in the `isa/*/settings.rs` modules.
315/// Each settings object provides a `predicate_view()` method that makes it possible to query
316/// ISA predicates by number.
317#[derive(Clone, Copy, Hash)]
318pub struct PredicateView<'a>(&'a [u8]);
319
320impl<'a> PredicateView<'a> {
321    /// Create a new view of a precomputed predicate vector.
322    ///
323    /// See the `predicate_view()` method on the various `Flags` types defined for each ISA.
324    pub fn new(bits: &'a [u8]) -> Self {
325        PredicateView(bits)
326    }
327
328    /// Check a numbered predicate.
329    pub fn test(self, p: usize) -> bool {
330        self.0[p / 8] & (1 << (p % 8)) != 0
331    }
332}
333
334/// Implementation details for generated code.
335///
336/// This module holds definitions that need to be public so the can be instantiated by generated
337/// code in other modules.
338pub mod detail {
339    use crate::constant_hash;
340    use core::fmt;
341    use core::hash::Hash;
342
343    /// An instruction group template.
344    #[derive(Hash)]
345    pub struct Template {
346        /// Name of the instruction group.
347        pub name: &'static str,
348        /// List of setting descriptors.
349        pub descriptors: &'static [Descriptor],
350        /// Union of all enumerators.
351        pub enumerators: &'static [&'static str],
352        /// Hash table of settings.
353        pub hash_table: &'static [u16],
354        /// Default values.
355        pub defaults: &'static [u8],
356        /// Pairs of (mask, value) for presets.
357        pub presets: &'static [(u8, u8)],
358    }
359
360    impl Template {
361        /// Get enumerators corresponding to a `Details::Enum`.
362        pub fn enums(&self, last: u8, enumerators: u16) -> &[&'static str] {
363            let from = enumerators as usize;
364            let len = usize::from(last) + 1;
365            &self.enumerators[from..from + len]
366        }
367
368        /// Format a setting value as a TOML string. This is mostly for use by the generated
369        /// `Display` implementation.
370        pub fn format_toml_value(
371            &self,
372            detail: Detail,
373            byte: u8,
374            f: &mut fmt::Formatter,
375        ) -> fmt::Result {
376            match detail {
377                Detail::Bool { bit } => write!(f, "{}", (byte & (1 << bit)) != 0),
378                Detail::Num => write!(f, "{byte}"),
379                Detail::Enum { last, enumerators } => {
380                    if byte <= last {
381                        let tags = self.enums(last, enumerators);
382                        write!(f, "\"{}\"", tags[usize::from(byte)])
383                    } else {
384                        write!(f, "{byte}")
385                    }
386                }
387                // Presets aren't printed. They are reflected in the other settings.
388                Detail::Preset { .. } => Ok(()),
389            }
390        }
391    }
392
393    /// The template contains a hash table for by-name lookup.
394    impl<'a> constant_hash::Table<&'a str> for Template {
395        fn len(&self) -> usize {
396            self.hash_table.len()
397        }
398
399        fn key(&self, idx: usize) -> Option<&'a str> {
400            let e = self.hash_table[idx] as usize;
401            if e < self.descriptors.len() {
402                Some(self.descriptors[e].name)
403            } else {
404                None
405            }
406        }
407    }
408
409    /// A setting descriptor holds the information needed to generically set and print a setting.
410    ///
411    /// Each settings group will be represented as a constant DESCRIPTORS array.
412    #[derive(Hash)]
413    pub struct Descriptor {
414        /// Lower snake-case name of setting as defined in meta.
415        pub name: &'static str,
416
417        /// The description of the setting.
418        pub description: &'static str,
419
420        /// Offset of byte containing this setting.
421        pub offset: u32,
422
423        /// Additional details, depending on the kind of setting.
424        pub detail: Detail,
425    }
426
427    /// The different kind of settings along with descriptor bits that depend on the kind.
428    #[derive(Clone, Copy, Hash)]
429    pub enum Detail {
430        /// A boolean setting only uses one bit, numbered from LSB.
431        Bool {
432            /// 0-7.
433            bit: u8,
434        },
435
436        /// A numerical setting uses the whole byte.
437        Num,
438
439        /// An Enum setting uses a range of enumerators.
440        Enum {
441            /// Numerical value of last enumerator, allowing for 1-256 enumerators.
442            last: u8,
443
444            /// First enumerator in the ENUMERATORS table.
445            enumerators: u16,
446        },
447
448        /// A preset is not an individual setting, it is a collection of settings applied at once.
449        ///
450        /// The `Descriptor::offset` field refers to the `PRESETS` table.
451        Preset,
452    }
453
454    impl Detail {
455        /// Check if a detail is a Detail::Preset. Useful because the Descriptor
456        /// offset field has a different meaning when the detail is a preset.
457        pub fn is_preset(self) -> bool {
458            match self {
459                Self::Preset => true,
460                _ => false,
461            }
462        }
463    }
464}
465
466// Include code generated by `meta/gen_settings.rs`. This file contains a public `Flags` struct
467// with an implementation for all of the settings defined in
468// `cranelift-codegen/meta/src/shared/settings.rs`.
469include!(concat!(env!("OUT_DIR"), "/settings.rs"));
470
471/// Wrapper containing flags and optionally a `TargetIsa` trait object.
472///
473/// A few passes need to access the flags but only optionally a target ISA. The `FlagsOrIsa`
474/// wrapper can be used to pass either, and extract the flags so they are always accessible.
475#[derive(Clone, Copy)]
476pub struct FlagsOrIsa<'a> {
477    /// Flags are always present.
478    pub flags: &'a Flags,
479
480    /// The ISA may not be present.
481    pub isa: Option<&'a dyn TargetIsa>,
482}
483
484impl<'a> From<&'a Flags> for FlagsOrIsa<'a> {
485    fn from(flags: &'a Flags) -> FlagsOrIsa<'a> {
486        FlagsOrIsa { flags, isa: None }
487    }
488}
489
490impl<'a> From<&'a dyn TargetIsa> for FlagsOrIsa<'a> {
491    fn from(isa: &'a dyn TargetIsa) -> FlagsOrIsa<'a> {
492        FlagsOrIsa {
493            flags: isa.flags(),
494            isa: Some(isa),
495        }
496    }
497}
498
499#[cfg(test)]
500mod tests {
501    use super::Configurable;
502    use super::SetError::*;
503    use super::{builder, Flags};
504    use alloc::string::ToString;
505
506    #[test]
507    fn display_default() {
508        let b = builder();
509        let f = Flags::new(b);
510        let actual = f.to_string();
511        let expected = r#"[shared]
512regalloc_algorithm = "backtracking"
513opt_level = "none"
514tls_model = "none"
515stack_switch_model = "none"
516libcall_call_conv = "isa_default"
517probestack_size_log2 = 12
518probestack_strategy = "outline"
519bb_padding_log2_minus_one = 0
520regalloc_checker = false
521regalloc_verbose_logs = false
522enable_alias_analysis = true
523enable_verifier = true
524enable_pcc = false
525is_pic = false
526use_colocated_libcalls = false
527enable_float = true
528enable_nan_canonicalization = false
529enable_pinned_reg = false
530enable_atomics = true
531enable_safepoints = false
532enable_llvm_abi_extensions = false
533enable_multi_ret_implicit_sret = false
534unwind_info = true
535preserve_frame_pointers = false
536machine_code_cfg_info = false
537enable_probestack = false
538enable_jump_tables = true
539enable_heap_access_spectre_mitigation = true
540enable_table_access_spectre_mitigation = true
541enable_incremental_compilation_cache_checks = false
542"#;
543        if actual != expected {
544            panic!(
545                "Default settings do not match expectations:\n\n{}",
546                similar::TextDiff::from_lines(expected, &actual)
547                    .unified_diff()
548                    .header("expected", "actual")
549            );
550        }
551        assert_eq!(f.opt_level(), super::OptLevel::None);
552    }
553
554    #[test]
555    fn modify_bool() {
556        let mut b = builder();
557        assert_eq!(b.enable("not_there"), Err(BadName("not_there".to_string())));
558        assert_eq!(b.enable("enable_atomics"), Ok(()));
559        assert_eq!(b.set("enable_atomics", "false"), Ok(()));
560
561        let f = Flags::new(b);
562        assert_eq!(f.enable_atomics(), false);
563    }
564
565    #[test]
566    fn modify_string() {
567        let mut b = builder();
568        assert_eq!(
569            b.set("not_there", "true"),
570            Err(BadName("not_there".to_string()))
571        );
572        assert_eq!(
573            b.set("enable_atomics", ""),
574            Err(BadValue("bool".to_string()))
575        );
576        assert_eq!(
577            b.set("enable_atomics", "best"),
578            Err(BadValue("bool".to_string()))
579        );
580        assert_eq!(
581            b.set("opt_level", "true"),
582            Err(BadValue(
583                "any among none, speed, speed_and_size".to_string()
584            ))
585        );
586        assert_eq!(b.set("opt_level", "speed"), Ok(()));
587        assert_eq!(b.set("enable_atomics", "0"), Ok(()));
588
589        let f = Flags::new(b);
590        assert_eq!(f.enable_atomics(), false);
591        assert_eq!(f.opt_level(), super::OptLevel::Speed);
592    }
593}
cranelift_codegen/settings.rs

cranelift_codegen/
settings.rs
