Add documentation for top-level items in cranelift-codegen/meta

cranelift/codegen/meta/src/cdsl/mod.rs

@@ -39,6 +39,7 @@ macro_rules! predicate {
     };
 }
 
+/// A macro that joins boolean settings into a list (e.g. `preset!(feature_a && feature_b)`).
 #[macro_export]
 macro_rules! preset {
     () => {

cranelift/codegen/meta/src/default_map.rs

@@ -1,3 +1,4 @@
+//! Trait for extending `HashMap` with `get_or_default`.
 use std::collections::HashMap;
 use std::hash::Hash;
 

cranelift/codegen/meta/src/error.rs

@@ -1,3 +1,4 @@
+//! Error returned during meta code-generation.
 use std::fmt;
 use std::io;
 

cranelift/codegen/meta/src/gen_inst.rs

@@ -1,3 +1,4 @@
+//! Generate instruction data (including opcodes, formats, builders, etc.).
 use std::fmt;
 
 use cranelift_codegen_shared::constant_hash;

cranelift/codegen/meta/src/gen_legalizer.rs

@@ -1,3 +1,4 @@
+//! Generate transformations to legalize instructions without encodings.
 use crate::cdsl::ast::{Def, DefPool, Expr, VarPool};
 use crate::cdsl::isa::TargetIsa;
 use crate::cdsl::operands::Operand;

cranelift/codegen/meta/src/gen_registers.rs

@@ -1,3 +1,4 @@
+//! Generate the ISA-specific registers.
 use crate::cdsl::isa::TargetIsa;
 use crate::cdsl::regs::{RegBank, RegClass};
 use crate::error;

cranelift/codegen/meta/src/gen_settings.rs

@@ -1,3 +1,4 @@
+//! Generate the ISA-specific settings.
 use std::collections::HashMap;
 
 use cranelift_codegen_shared::constant_hash::{generate_table, simple_hash};

cranelift/codegen/meta/src/isa/mod.rs

@@ -1,3 +1,4 @@
+//! Define supported ISAs; includes ISA-specific instructions, encodings, registers, settings, etc.
 use crate::cdsl::isa::TargetIsa;
 use crate::shared::Definitions as SharedDefinitions;
 use std::fmt;

cranelift/codegen/meta/src/lib.rs

@@ -1,3 +1,5 @@
+//! This crate generates Rust sources for use by
+//! [`cranelift_codegen`](../cranelift_codegen/index.html).
 #[macro_use]
 mod cdsl;
 mod srcgen;
@@ -17,6 +19,7 @@ mod default_map;
 mod shared;
 mod unique_table;
 
+/// Generate an ISA from an architecture string (e.g. "x86_64").
 pub fn isa_from_arch(arch: &str) -> Result<isa::Isa, String> {
     isa::Isa::from_arch(arch).ok_or_else(|| format!("no supported isa found for arch `{}`", arch))
 }

cranelift/codegen/meta/src/unique_table.rs

@@ -1,3 +1,4 @@
+//! An index-accessed table implementation that avoids duplicate entries.
 use std::collections::HashMap;
 use std::hash::Hash;
 use std::slice;