Cc updates #438
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Cc updates #438
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Changes Made
1. Extended IR Initializer enum (ir/mod.rs):
- Added String(String) for char array string literals
- Added Array { elem_size, total_size, elements } for array initializers
- Added Struct { total_size, fields } for struct initializers (with field
sizes)
- Added SymAddr(String) for address-of symbol references
2. Updated linearizer (ir/linearize.rs):
- Added ast_init_to_ir() to convert AST expressions to IR Initializers
- Added ast_init_list_to_ir() to handle {} initializer lists
- Supports designated initializers (.field = value, [index] = value)
- Sorts elements by offset to handle out-of-order designators
- Updated both linearize_global_decl() and linearize_static_local()
3. Added new directive (arch/lir.rs):
- Added Ascii(String) for non-null-terminated strings
- Added QuadSym(Symbol) for 64-bit symbol address relocations
4. Updated codegen (both arch/x86_64/codegen.rs and
arch/aarch64/codegen.rs):
- Added emit_initializer_data() to recursively emit complex initializers
- Handles proper padding/gaps between array elements and struct fields
- Emits correct size directives (.byte, .short, .long, .quad)
5. Added tests (tests/globals/mod.rs):
- test_global_array_init - basic array initializer
- test_global_array_partial_init - partial array init (rest zeros)
- test_global_array_designated - [index] = value syntax
- test_global_struct_init - basic struct initializer
- test_global_struct_designated - .field = value syntax
- test_global_struct_partial_init - partial struct init
- test_global_string_array - char array from string literal
- test_static_local_array - static local array
- test_static_local_struct - static local struct
Changes Made
1. Parser (parse/parser.rs)
- Enhanced eval_const_expr to support:
- sizeof(type) and sizeof(expr)
- Cast expressions
- All comparison operators (were already there)
- Conditional expressions (were already there)
- Fixed array size parsing (2 locations at lines ~3244 and ~3877):
- Was: Only handled IntLit directly
- Now: Uses eval_const_expr to handle full constant expressions like 2 +
3, sizeof(int) * 2, X + Y (enum constants)
2. Linearizer (ir/linearize.rs)
- Enhanced eval_const_expr to match the parser's capabilities (sizeof,
casts, conditionals, all operators)
- Enhanced ast_init_to_ir to:
- Handle enum constants in initializers
- Use eval_const_expr as a fallback for any expression that might be
constant (handles int x = 2 + 3;)
3. Tests (tests/globals/mod.rs)
- Added 3 new tests:
- test_global_const_expr_init: Tests int x = 2 + 3;, 10 * 4 + 2, (1 <<
4) | 10, etc.
- test_array_const_expr_size: Tests int arr[2 + 3];, int arr[sizeof(int)
* 2];
- test_enum_const_expr: Tests using enum constants in array sizes and
initializers
4. Documentation
- Removed "constant expression evaluation" from the "not yet implemented"
list in README.md
jgarzik
added
documentation
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Pull request overview
This PR adds comprehensive support for C99/C11 features including the noreturn attribute, several GCC-style builtins (__builtin_ctz*, __builtin_unreachable), setjmp/longjmp non-local jumps, and complex global/static initializers (arrays, structs, designated initializers). The implementation includes type system updates, parser enhancements, IR extensions, architecture-specific code generation for both x86-64 and AArch64, dead code elimination optimizations, extensive test coverage, and detailed documentation.
Key Changes:
- Added
noreturnfunction attribute support (__attribute__((noreturn))and_Noreturnkeyword) with proper type system integration - Implemented count trailing zeros builtins (
__builtin_ctz,__builtin_ctzl,__builtin_ctzll) with native instruction support (BSF on x86-64, RBIT+CLZ on AArch64) - Added
__builtin_unreachable()for optimization hints with trap instructions (UD2/BRK) and DCE integration - Implemented setjmp/longjmp for non-local control flow with proper ABI-compliant code generation
- Enhanced constant expression evaluation to support sizeof, casts, and complex expressions for array sizes and initializers
- Added complex initializer support (arrays, structs, strings, designated initializers, symbol addresses) with proper zero-padding and offset handling
Reviewed changes
Copilot reviewed 25 out of 25 changed files in this pull request and generated 2 comments.
Show a summary per file
| File | Description |
|---|---|
| cc/types.rs | Added NORETURN type modifier flag and noreturn field to Type struct for function types |
| cc/token/preprocess.rs | Updated __has_attribute and __has_builtin to report support for noreturn and new builtins |
| cc/parse/parser.rs | Added parsing for _Noreturn keyword, ctz/unreachable/setjmp/longjmp builtins, enhanced constant expression evaluation |
| cc/parse/ast.rs | Added AST nodes for Ctz/Ctzl/Ctzll, Unreachable, Setjmp, and Longjmp expressions |
| cc/ir/mod.rs | Added IR opcodes and initializer variants for new features |
| cc/ir/linearize.rs | Implemented linearization for new builtins, enhanced global initializer handling, added inline function semantic checks |
| cc/ir/dce.rs | Extended DCE to handle unreachable blocks and fold branches to unreachable |
| cc/arch/x86_64/lir.rs | Added UD2 (trap) and BSF (bit scan forward) x86-64 instructions |
| cc/arch/x86_64/codegen.rs | Implemented code generation for all new features with proper initializer emission |
| cc/arch/aarch64/lir.rs | Added BRK (trap), RBIT, and CLZ AArch64 instructions |
| cc/arch/aarch64/codegen.rs | Implemented AArch64 code generation for all new features |
| cc/arch/lir.rs | Added .ascii directive and QuadSym for symbol address relocations |
| cc/tests/globals/mod.rs | Added comprehensive tests for global/static array and struct initializers |
| cc/tests/features/*.rs | Added test files for noreturn, unreachable, setjmp, inline, and ctz builtins |
| cc/doc/ATTR.md | New documentation file for function attributes |
| cc/doc/BUILTIN.md | Updated with documentation for new builtins |
| cc/doc/README.md | New documentation index |
| cc/README.md | Updated limitations list to reflect implemented features |
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and clippy warning fix
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