diff options
Diffstat (limited to 'backends/cxxrtl/cxxrtl_capi.h')
| -rw-r--r-- | backends/cxxrtl/cxxrtl_capi.h | 129 |
1 files changed, 121 insertions, 8 deletions
diff --git a/backends/cxxrtl/cxxrtl_capi.h b/backends/cxxrtl/cxxrtl_capi.h index 46aa662b2..385d6dcf3 100644 --- a/backends/cxxrtl/cxxrtl_capi.h +++ b/backends/cxxrtl/cxxrtl_capi.h @@ -26,6 +26,7 @@ #include <stddef.h> #include <stdint.h> +#include <assert.h> #ifdef __cplusplus extern "C" { @@ -54,12 +55,28 @@ cxxrtl_handle cxxrtl_create(cxxrtl_toplevel design); // Release all resources used by a design and its handle. void cxxrtl_destroy(cxxrtl_handle handle); +// Evaluate the design, propagating changes on inputs to the `next` value of internal state and +// output wires. +// +// Returns 1 if the design is known to immediately converge, 0 otherwise. +int cxxrtl_eval(cxxrtl_handle handle); + +// Commit the design, replacing the `curr` value of internal state and output wires with the `next` +// value. +// +// Return 1 if any of the `curr` values were updated, 0 otherwise. +int cxxrtl_commit(cxxrtl_handle handle); + // Simulate the design to a fixed point. // // Returns the number of delta cycles. size_t cxxrtl_step(cxxrtl_handle handle); // Type of a simulated object. +// +// The type of a simulated object indicates the way it is stored and the operations that are legal +// to perform on it (i.e. won't crash the simulation). It says very little about object semantics, +// which is specified through flags. enum cxxrtl_type { // Values correspond to singly buffered netlist nodes, i.e. nodes driven exclusively by // combinatorial cells, or toplevel input nodes. @@ -73,7 +90,8 @@ enum cxxrtl_type { CXXRTL_VALUE = 0, // Wires correspond to doubly buffered netlist nodes, i.e. nodes driven, at least in part, by - // storage cells, or by combinatorial cells that are a part of a feedback path. + // storage cells, or by combinatorial cells that are a part of a feedback path. They are also + // present in non-optimized builds. // // Wires can be inspected via the `curr` pointer and modified via the `next` pointer (which are // distinct for wires). Note that changes to the bits driven by combinatorial cells will be @@ -89,7 +107,74 @@ enum cxxrtl_type { // always NULL. CXXRTL_MEMORY = 2, - // More object types will be added in the future, but the existing ones will never change. + // Aliases correspond to netlist nodes driven by another node such that their value is always + // exactly equal. + // + // Aliases can be inspected via the `curr` pointer. They cannot be modified, and the `next` + // pointer is always NULL. + CXXRTL_ALIAS = 3, + + // More object types may be added in the future, but the existing ones will never change. +}; + +// Flags of a simulated object. +// +// The flags of a simulated object indicate its role in the netlist: +// * The flags `CXXRTL_INPUT` and `CXXRTL_OUTPUT` designate module ports. +// * The flags `CXXRTL_DRIVEN_SYNC`, `CXXRTL_DRIVEN_COMB`, and `CXXRTL_UNDRIVEN` specify +// the semantics of node state. An object with several of these flags set has different bits +// follow different semantics. +enum cxxrtl_flag { + // Node is a module input port. + // + // This flag can be set on objects of type `CXXRTL_VALUE` and `CXXRTL_WIRE`. It may be combined + // with `CXXRTL_OUTPUT`, as well as other flags. + CXXRTL_INPUT = 1 << 0, + + // Node is a module output port. + // + // This flag can be set on objects of type `CXXRTL_WIRE`. It may be combined with `CXXRTL_INPUT`, + // as well as other flags. + CXXRTL_OUTPUT = 1 << 1, + + // Node is a module inout port. + // + // This flag can be set on objects of type `CXXRTL_WIRE`. It may be combined with other flags. + CXXRTL_INOUT = (CXXRTL_INPUT|CXXRTL_OUTPUT), + + // Node has bits that are driven by a storage cell. + // + // This flag can be set on objects of type `CXXRTL_WIRE`. It may be combined with + // `CXXRTL_DRIVEN_COMB` and `CXXRTL_UNDRIVEN`, as well as other flags. + // + // This flag is set on wires that have bits connected directly to the output of a flip-flop or + // a latch, and hold its state. Many `CXXRTL_WIRE` objects may not have the `CXXRTL_DRIVEN_SYNC` + // flag set; for example, output ports and feedback wires generally won't. Writing to the `next` + // pointer of these wires updates stored state, and for designs without combinatorial loops, + // capturing the value from every of these wires through the `curr` pointer creates a complete + // snapshot of the design state. + CXXRTL_DRIVEN_SYNC = 1 << 2, + + // Node has bits that are driven by a combinatorial cell or another node. + // + // This flag can be set on objects of type `CXXRTL_VALUE` and `CXXRTL_WIRE`. It may be combined + // with `CXXRTL_DRIVEN_SYNC` and `CXXRTL_UNDRIVEN`, as well as other flags. + // + // This flag is set on objects that have bits connected to the output of a combinatorial cell, + // or directly to another node. For designs without combinatorial loops, writing to such bits + // through the `next` pointer (if it is not NULL) has no effect. + CXXRTL_DRIVEN_COMB = 1 << 3, + + // Node has bits that are not driven. + // + // This flag can be set on objects of type `CXXRTL_VALUE` and `CXXRTL_WIRE`. It may be combined + // with `CXXRTL_DRIVEN_SYNC` and `CXXRTL_DRIVEN_COMB`, as well as other flags. + // + // This flag is set on objects that have bits not driven by an output of any cell or by another + // node, such as inputs and dangling wires. + CXXRTL_UNDRIVEN = 1 << 4, + + // More object flags may be added in the future, but the existing ones will never change. }; // Description of a simulated object. @@ -103,12 +188,21 @@ struct cxxrtl_object { // determines all other properties of the object. uint32_t type; // actually `enum cxxrtl_type` + // Flags of the object. + uint32_t flags; // actually bit mask of `enum cxxrtl_flags` + // Width of the object in bits. size_t width; + // Index of the least significant bit. + size_t lsb_at; + // Depth of the object. Only meaningful for memories; for other objects, always 1. size_t depth; + // Index of the first word. Only meaningful for memories; for other objects, always 0; + size_t zero_at; + // Bits stored in the object, as 32-bit chunks, least significant bits first. // // The width is rounded up to a multiple of 32; the padding bits are always set to 0 by @@ -123,7 +217,7 @@ struct cxxrtl_object { uint32_t *curr; uint32_t *next; - // More description fields will be added in the future, but the existing ones will never change. + // More description fields may be added in the future, but the existing ones will never change. }; // Retrieve description of a simulated object. @@ -133,17 +227,36 @@ struct cxxrtl_object { // the top-level module instantiates a module `foo`, which in turn contains a wire `bar`, the full // hierarchical name is `\foo \bar`. // -// Returns the object if it was found, NULL otherwise. The returned value is valid until the design -// is destroyed. -struct cxxrtl_object *cxxrtl_get(cxxrtl_handle handle, const char *name); +// The storage of a single abstract object may be split (usually with the `splitnets` pass) into +// many physical parts, all of which correspond to the same hierarchical name. To handle such cases, +// this function returns an array and writes its length to `parts`. The array is sorted by `lsb_at`. +// +// Returns the object parts if it was found, NULL otherwise. The returned parts are valid until +// the design is destroyed. +struct cxxrtl_object *cxxrtl_get_parts(cxxrtl_handle handle, const char *name, size_t *parts); + +// Retrieve description of a single part simulated object. +// +// This function is a shortcut for the most common use of `cxxrtl_get_parts`. It asserts that, +// if the object exists, it consists of a single part. If assertions are disabled, it returns NULL +// for multi-part objects. +inline struct cxxrtl_object *cxxrtl_get(cxxrtl_handle handle, const char *name) { + size_t parts = 0; + struct cxxrtl_object *object = cxxrtl_get_parts(handle, name, &parts); + assert(object == NULL || parts == 1); + if (object == NULL || parts == 1) + return object; + return NULL; +} // Enumerate simulated objects. // // For every object in the simulation, `callback` is called with the provided `data`, the full -// hierarchical name of the object (see `cxxrtl_get` for details), and the object description. +// hierarchical name of the object (see `cxxrtl_get` for details), and the object parts. // The provided `name` and `object` values are valid until the design is destroyed. void cxxrtl_enum(cxxrtl_handle handle, void *data, - void (*callback)(void *data, const char *name, struct cxxrtl_object *object)); + void (*callback)(void *data, const char *name, + struct cxxrtl_object *object, size_t parts)); #ifdef __cplusplus } |