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* Atomic Operation Generators (ADR-053 A3)
*
* Generates C code for atomic Read-Modify-Write operations (ADR-049):
* - LDREX/STREX loops for platforms with exclusive access support
* - PRIMASK-based wrappers for interrupt-safe operations
*
* These are helper functions called from assignment generation,
* not top-level statement generators.
*/
import TTypeInfo from "../../types/TTypeInfo";
import IGeneratorOutput from "../IGeneratorOutput";
import TGeneratorEffect from "../TGeneratorEffect";
import ITargetCapabilities from "../../types/ITargetCapabilities";
import TYPE_WIDTH from "../../types/TYPE_WIDTH";
/**
* Maps C-Next types to C types (for atomic operations)
*/
const TYPE_MAP: Record<string, string> = {
u8: "uint8_t",
u16: "uint16_t",
u32: "uint32_t",
u64: "uint64_t",
i8: "int8_t",
i16: "int16_t",
i32: "int32_t",
i64: "int64_t",
};
/**
* ADR-049: LDREX intrinsic map for atomic operations
* Maps C-Next types to ARM LDREX (Load-Exclusive) instructions
*/
const LDREX_MAP: Record<string, string> = {
u8: "__LDREXB",
i8: "__LDREXB",
u16: "__LDREXH",
i16: "__LDREXH",
u32: "__LDREXW",
i32: "__LDREXW",
};
/**
* ADR-049: STREX intrinsic map for atomic operations
* Maps C-Next types to ARM STREX (Store-Exclusive) instructions
*/
const STREX_MAP: Record<string, string> = {
u8: "__STREXB",
i8: "__STREXB",
u16: "__STREXH",
i16: "__STREXH",
u32: "__STREXW",
i32: "__STREXW",
};
/**
* Map compound operators to simple operators
*/
const SIMPLE_OP_MAP: Record<string, string> = {
"+=": "+",
"-=": "-",
"*=": "*",
"/=": "/",
"%=": "%",
"&=": "&",
"|=": "|",
"^=": "^",
"<<=": "<<",
">>=": ">>",
};
/**
* Map compound operators to clamp helper operation names
*/
const CLAMP_OP_MAP: Record<string, string> = {
"+=": "add",
"-=": "sub",
"*=": "mul",
};
/**
* Check if clamp behavior applies and return helper operation name.
* Returns null if clamp doesn't apply (wrap behavior, float, or unsupported op).
*/
function getClampHelperOp(cOp: string, typeInfo: TTypeInfo): string | null {
if (
typeInfo.overflowBehavior === "clamp" &&
TYPE_WIDTH[typeInfo.baseType] &&
!typeInfo.baseType.startsWith("f") // Floats use native C arithmetic
) {
return CLAMP_OP_MAP[cOp] || null;
}
return null;
}
/**
* Generate the inner operation for atomic RMW.
* Handles clamp/wrap behavior for arithmetic operations.
*
* @returns Object with code and effects (may include helper effects for clamp)
*/
function generateInnerAtomicOp(
cOp: string,
value: string,
typeInfo: TTypeInfo,
): IGeneratorOutput {
const effects: TGeneratorEffect[] = [];
const simpleOp = SIMPLE_OP_MAP[cOp] || "+";
// Handle clamp behavior for arithmetic operations (integers only)
const helperOp = getClampHelperOp(cOp, typeInfo);
if (helperOp) {
effects.push({
type: "helper",
operation: helperOp,
cnxType: typeInfo.baseType,
});
return {
code: `cnx_clamp_${helperOp}_${typeInfo.baseType}(__old, ${value})`,
effects,
};
}
// For wrap behavior, floats, or non-clamp ops, use natural arithmetic
return { code: `__old ${simpleOp} ${value}`, effects };
}
/**
* Generate LDREX/STREX retry loop for atomic RMW.
* Uses ARM exclusive access instructions for lock-free atomics.
*
* @returns Object with code and effects (includes cmsis header)
*/
function generateLdrexStrexLoop(
target: string,
innerOp: string,
typeInfo: TTypeInfo,
innerEffects: readonly TGeneratorEffect[],
): IGeneratorOutput {
const effects: TGeneratorEffect[] = [...innerEffects];
const ldrex = LDREX_MAP[typeInfo.baseType];
const strex = STREX_MAP[typeInfo.baseType];
const cType = TYPE_MAP[typeInfo.baseType];
// Mark that we need CMSIS headers
effects.push({ type: "include", header: "cmsis" });
// Generate LDREX/STREX retry loop
// Uses do-while because we always need at least one attempt
const code = `do {
${cType} __old = ${ldrex}(&${target});
${cType} __new = ${innerOp};
if (${strex}(__new, &${target}) == 0) break;
} while (1);`;
return { code, effects };
}
/**
* Generate PRIMASK-based atomic wrapper.
* Disables all interrupts during the RMW operation.
*
* @returns Object with code and effects (includes cmsis header, may include helper)
*/
function generatePrimaskWrapper(
target: string,
cOp: string,
value: string,
typeInfo: TTypeInfo,
): IGeneratorOutput {
const effects: TGeneratorEffect[] = [];
// Mark that we need CMSIS headers
effects.push({ type: "include", header: "cmsis" });
// Generate the actual assignment operation inside the critical section
let assignment: string;
// Handle clamp behavior (integers only)
const helperOp = getClampHelperOp(cOp, typeInfo);
if (helperOp) {
effects.push({
type: "helper",
operation: helperOp,
cnxType: typeInfo.baseType,
});
assignment = `${target} = cnx_clamp_${helperOp}_${typeInfo.baseType}(${target}, ${value});`;
} else {
assignment = `${target} ${cOp} ${value};`;
}
// Generate PRIMASK save/restore wrapper
const code = `{
uint32_t __primask = __get_PRIMASK();
__disable_irq();
${assignment}
__set_PRIMASK(__primask);
}`;
return { code, effects };
}
/**
* ADR-049: Generate atomic Read-Modify-Write operation.
* Uses LDREX/STREX on platforms that support it, otherwise PRIMASK.
*
* @param target - The target variable expression
* @param cOp - The C compound assignment operator (+=, -=, etc.)
* @param value - The value expression
* @param typeInfo - Type information for the target
* @param targetCapabilities - Platform capabilities
* @returns Generated code and effects
*/
function generateAtomicRMW(
target: string,
cOp: string,
value: string,
typeInfo: TTypeInfo,
targetCapabilities: ITargetCapabilities,
): IGeneratorOutput {
const baseType = typeInfo.baseType;
// Generate the inner operation (handles clamp/wrap)
const innerResult = generateInnerAtomicOp(cOp, value, typeInfo);
// Use LDREX/STREX if available for this type, otherwise PRIMASK fallback
if (targetCapabilities.hasLdrexStrex && LDREX_MAP[baseType]) {
return generateLdrexStrexLoop(
target,
innerResult.code,
typeInfo,
innerResult.effects,
);
} else {
return generatePrimaskWrapper(target, cOp, value, typeInfo);
}
}
// Export all atomic generators
const atomicGenerators = {
generateAtomicRMW,
generateInnerAtomicOp,
generateLdrexStrexLoop,
generatePrimaskWrapper,
};
export default atomicGenerators;
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