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/// Implementation details for generated code.
313///
314/// This module holds definitions that need to be public so the can be instantiated by generated
315/// code in other modules.
316pub mod detail {
317    use crate::constant_hash;
318    use core::fmt;
319    use core::hash::Hash;
320
321    /// An instruction group template.
322    #[derive(Hash)]
323    pub struct Template {
324        /// Name of the instruction group.
325        pub name: &'static str,
326        /// List of setting descriptors.
327        pub descriptors: &'static [Descriptor],
328        /// Union of all enumerators.
329        pub enumerators: &'static [&'static str],
330        /// Hash table of settings.
331        pub hash_table: &'static [u16],
332        /// Default values.
333        pub defaults: &'static [u8],
334        /// Pairs of (mask, value) for presets.
335        pub presets: &'static [(u8, u8)],
336    }
337
338    impl Template {
339        /// Get enumerators corresponding to a `Details::Enum`.
340        pub fn enums(&self, last: u8, enumerators: u16) -> &[&'static str] {
341            let from = enumerators as usize;
342            let len = usize::from(last) + 1;
343            &self.enumerators[from..from + len]
344        }
345
346        /// Format a setting value as a TOML string. This is mostly for use by the generated
347        /// `Display` implementation.
348        pub fn format_toml_value(
349            &self,
350            detail: Detail,
351            byte: u8,
352            f: &mut fmt::Formatter,
353        ) -> fmt::Result {
354            match detail {
355                Detail::Bool { bit } => write!(f, "{}", (byte & (1 << bit)) != 0),
356                Detail::Num => write!(f, "{byte}"),
357                Detail::Enum { last, enumerators } => {
358                    if byte <= last {
359                        let tags = self.enums(last, enumerators);
360                        write!(f, "\"{}\"", tags[usize::from(byte)])
361                    } else {
362                        write!(f, "{byte}")
363                    }
364                }
365                // Presets aren't printed. They are reflected in the other settings.
366                Detail::Preset { .. } => Ok(()),
367            }
368        }
369    }
370
371    /// The template contains a hash table for by-name lookup.
372    impl<'a> constant_hash::Table<&'a str> for Template {
373        fn len(&self) -> usize {
374            self.hash_table.len()
375        }
376
377        fn key(&self, idx: usize) -> Option<&'a str> {
378            let e = self.hash_table[idx] as usize;
379            if e < self.descriptors.len() {
380                Some(self.descriptors[e].name)
381            } else {
382                None
383            }
384        }
385    }
386
387    /// A setting descriptor holds the information needed to generically set and print a setting.
388    ///
389    /// Each settings group will be represented as a constant DESCRIPTORS array.
390    #[derive(Hash)]
391    pub struct Descriptor {
392        /// Lower snake-case name of setting as defined in meta.
393        pub name: &'static str,
394
395        /// The description of the setting.
396        pub description: &'static str,
397
398        /// Offset of byte containing this setting.
399        pub offset: u32,
400
401        /// Additional details, depending on the kind of setting.
402        pub detail: Detail,
403    }
404
405    /// The different kind of settings along with descriptor bits that depend on the kind.
406    #[derive(Clone, Copy, Hash)]
407    pub enum Detail {
408        /// A boolean setting only uses one bit, numbered from LSB.
409        Bool {
410            /// 0-7.
411            bit: u8,
412        },
413
414        /// A numerical setting uses the whole byte.
415        Num,
416
417        /// An Enum setting uses a range of enumerators.
418        Enum {
419            /// Numerical value of last enumerator, allowing for 1-256 enumerators.
420            last: u8,
421
422            /// First enumerator in the ENUMERATORS table.
423            enumerators: u16,
424        },
425
426        /// A preset is not an individual setting, it is a collection of settings applied at once.
427        ///
428        /// The `Descriptor::offset` field refers to the `PRESETS` table.
429        Preset,
430    }
431
432    impl Detail {
433        /// Check if a detail is a Detail::Preset. Useful because the Descriptor
434        /// offset field has a different meaning when the detail is a preset.
435        pub fn is_preset(self) -> bool {
436            match self {
437                Self::Preset => true,
438                _ => false,
439            }
440        }
441    }
442}
443
444// Include code generated by `meta/gen_settings.rs`. This file contains a public `Flags` struct
445// with an implementation for all of the settings defined in
446// `cranelift-codegen/meta/src/shared/settings.rs`.
447include!(concat!(env!("OUT_DIR"), "/settings.rs"));
448
449/// Wrapper containing flags and optionally a `TargetIsa` trait object.
450///
451/// A few passes need to access the flags but only optionally a target ISA. The `FlagsOrIsa`
452/// wrapper can be used to pass either, and extract the flags so they are always accessible.
453#[derive(Clone, Copy)]
454pub struct FlagsOrIsa<'a> {
455    /// Flags are always present.
456    pub flags: &'a Flags,
457
458    /// The ISA may not be present.
459    pub isa: Option<&'a dyn TargetIsa>,
460}
461
462impl<'a> From<&'a Flags> for FlagsOrIsa<'a> {
463    fn from(flags: &'a Flags) -> FlagsOrIsa<'a> {
464        FlagsOrIsa { flags, isa: None }
465    }
466}
467
468impl<'a> From<&'a dyn TargetIsa> for FlagsOrIsa<'a> {
469    fn from(isa: &'a dyn TargetIsa) -> FlagsOrIsa<'a> {
470        FlagsOrIsa {
471            flags: isa.flags(),
472            isa: Some(isa),
473        }
474    }
475}
476
477#[cfg(test)]
478mod tests {
479    use super::Configurable;
480    use super::SetError::*;
481    use super::{Flags, builder};
482    use alloc::string::ToString;
483
484    #[test]
485    fn display_default() {
486        let b = builder();
487        let f = Flags::new(b);
488        let actual = f.to_string();
489        let expected = r#"[shared]
490regalloc_algorithm = "backtracking"
491opt_level = "none"
492tls_model = "none"
493stack_switch_model = "none"
494libcall_call_conv = "isa_default"
495probestack_size_log2 = 12
496probestack_strategy = "outline"
497bb_padding_log2_minus_one = 0
498log2_min_function_alignment = 0
499regalloc_checker = false
500regalloc_verbose_logs = false
501enable_alias_analysis = true
502enable_verifier = true
503enable_pcc = false
504is_pic = false
505use_colocated_libcalls = false
506enable_float = true
507enable_nan_canonicalization = false
508enable_pinned_reg = false
509enable_atomics = true
510enable_safepoints = false
511enable_llvm_abi_extensions = false
512enable_multi_ret_implicit_sret = false
513unwind_info = true
514preserve_frame_pointers = false
515machine_code_cfg_info = false
516enable_probestack = false
517enable_jump_tables = true
518enable_heap_access_spectre_mitigation = true
519enable_table_access_spectre_mitigation = true
520enable_incremental_compilation_cache_checks = false
521"#;
522        if actual != expected {
523            panic!(
524                "Default settings do not match expectations:\n\n{}",
525                similar::TextDiff::from_lines(expected, &actual)
526                    .unified_diff()
527                    .header("expected", "actual")
528            );
529        }
530        assert_eq!(f.opt_level(), super::OptLevel::None);
531    }
532
533    #[test]
534    fn modify_bool() {
535        let mut b = builder();
536        assert_eq!(b.enable("not_there"), Err(BadName("not_there".to_string())));
537        assert_eq!(b.enable("enable_atomics"), Ok(()));
538        assert_eq!(b.set("enable_atomics", "false"), Ok(()));
539
540        let f = Flags::new(b);
541        assert_eq!(f.enable_atomics(), false);
542    }
543
544    #[test]
545    fn modify_string() {
546        let mut b = builder();
547        assert_eq!(
548            b.set("not_there", "true"),
549            Err(BadName("not_there".to_string()))
550        );
551        assert_eq!(
552            b.set("enable_atomics", ""),
553            Err(BadValue("bool".to_string()))
554        );
555        assert_eq!(
556            b.set("enable_atomics", "best"),
557            Err(BadValue("bool".to_string()))
558        );
559        assert_eq!(
560            b.set("opt_level", "true"),
561            Err(BadValue(
562                "any among none, speed, speed_and_size".to_string()
563            ))
564        );
565        assert_eq!(b.set("opt_level", "speed"), Ok(()));
566        assert_eq!(b.set("enable_atomics", "0"), Ok(()));
567
568        let f = Flags::new(b);
569        assert_eq!(f.enable_atomics(), false);
570        assert_eq!(f.opt_level(), super::OptLevel::Speed);
571    }
572}
cranelift_codegen/settings.rs

cranelift_codegen/
settings.rs
