feat(sv): support $sformatf and $sformat by tignear · Pull Request #2402 · celox-sim/celox

tignear · 2026-10-28T07:18:09Z

Implement formatting to a string (IEEE 1800-2023 21.3.3). The analyzer binds
$sformatf(format, args...) as a string operation, so it is typed string
wherever a string value is valid: assignments, function results, arguments,
concatenations and conditional operands. $sformat(output, format, args...)
assigns the same value to a string variable, a function's return variable or
a string class property.

A call with conversions is a synchronous host request of the scheduled
process. The host renders the format with the $display renderer, so every
conversion, field width, X/Z digit and %m scope matches $display, and
interns the text as the result. A literal format is fixed at compile time and
its %t values are scaled as the analyzer scales those of $display; a
string or integral format is read when the call runs and the host scales
its %t values. A literal without conversions or arguments is a constant.
Integral outputs, %p and the $swrite family remain unsupported.

A host request in a later input of a subroutine call would otherwise lose the
registers computed for earlier inputs across the suspension, so those inputs
are kept, converted to their formals, in temporaries; operands of string,
object and container operations are materialized as the heap helpers already
do. A cached transitive check finds subroutines
that make host requests, including in the defaults of omitted arguments. A
format read at run time keeps bytes that are not UTF-8.
$display now resolves every string-valued argument, not only string
identifiers, so a string conditional prints its text.

The shared string_format cases compare $sformatf and $sformat with
$display on all backends and in a native image. Verilator 5.052 passes all
of them (the four-state case is unsupported there); Icarus 13.0 limitations
(string conditional crash, class-property output, integral format) and an
xezim 0.11.3 integral-format bug are retained with evidence.

tignear · 2026-10-28T07:18:12Z

This pull request is part of a Mergify stack:

#	Pull Request	Link
1	feat(sv): support $sformatf and $sformat	#2402	👈
2	feat(sv): support the $swrite family	#2403
3	feat(sv): support %p for integral, string, handle and container values	#2423

chatgpt-codex-connector · 2026-10-28T07:18:21Z

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-28T17:55:36.202429Z	`242cd1f`	New commits

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mergify · 2026-10-28T08:01:02Z

Queued — the merge queue status continues in this comment ↓.

tignear · 2026-10-28T08:40:59Z

Revision history

#	Type	Changes	Reason	Date
1	initial	`290e018`		2026-10-28 08:40 UTC
2	content	`290e018 → 27e5a3d`	Address Codex review 5679124714: check omitted-argument defaults (and nested defaults) when deciding whether a call can make a host request, evaluate subroutine inputs before a later host request, an…	2026-10-28 08:40 UTC
3	content	`27e5a3d → d484bec`		2026-10-28 10:18 UTC
4	content	`d484bec → 3703011`		2026-10-28 11:31 UTC
5	content	`3703011 → f7aeb22`	Sync with master after #2322: Format host requests use family 7 (Process took 6), and $sformatf bypasses the new operand materialization in string_call, which truncated its format literal to 32 bits.	2026-10-28 12:53 UTC
6	content	`f7aeb22 → 5ab0f09`		2026-10-28 13:52 UTC
7	content	`5ab0f09 → bfa9061`		2026-10-28 16:23 UTC
8	content	`bfa9061 → 242cd1f`		2026-10-28 17:51 UTC

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mergify · 2026-10-28T14:50:59Z

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Implement formatting to a string (IEEE 1800-2023 21.3.3). The analyzer binds `$sformatf(format, args...)` as a string operation, so it is typed `string` wherever a string value is valid: assignments, function results, arguments, concatenations and conditional operands. `$sformat(output, format, args...)` assigns the same value to a string variable, a function's return variable or a string class property. A call with conversions is a synchronous host request of the scheduled process. The host renders the format with the `$display` renderer, so every conversion, field width, X/Z digit and `%m` scope matches `$display`, and interns the text as the result. A literal format is fixed at compile time and its `%t` values are scaled as the analyzer scales those of `$display`; a `string` or integral format is read when the call runs and the host scales its `%t` values. A literal without conversions or arguments is a constant. Integral outputs, `%p` and the `$swrite` family remain unsupported. A host request in a later input of a subroutine call would otherwise lose the registers computed for earlier inputs across the suspension, so those inputs are kept, converted to their formals, in temporaries; operands of string, object and container operations are materialized as the heap helpers already do. A cached transitive check finds subroutines that make host requests, including in the defaults of omitted arguments. A format read at run time keeps bytes that are not UTF-8. `$display` now resolves every string-valued argument, not only string identifiers, so a string conditional prints its text. The shared string_format cases compare `$sformatf` and `$sformat` with `$display` on all backends and in a native image. Verilator 5.052 passes all of them (the four-state case is unsupported there); Icarus 13.0 limitations (string conditional crash, class-property output, integral format) and an xezim 0.11.3 integral-format bug are retained with evidence. Change-Id: Ife5fd5bc64ccbecb7a73976fc8b68f22e5216d53

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chatgpt-codex-connector · 2026-10-28T17:55:32Z

+        Ok(sv::ir::Expr::Ident(name))
+    }


Preserve DPI-C inputs across formatting host requests

With sv-dpi enabled, a formatting request in a later DPI-C argument leaves earlier arguments live in registers across suspension. For example, combine(a, formatted_length()), where formatted_length() calls $sformatf and returns the resulting string's length, reaches Ff::dpi_call, which evaluates and retains a in registers before hoisting the second argument (ff.rs:1993–2018). The formatting request resumes through a new kernel invocation, so that earlier register is no longer available when the ExternCall executes. The new input-preservation logic only covers ordinary subroutine calls; apply equivalent formal-type-aware capture and reload to DPI-C arguments as well.

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mergify · 2026-10-28T18:17:52Z

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✅ Entered the queue Wed 28 Oct, 18:17 · rule changes · triggered by rule Queue explicitly requested merges
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Conflicting file: crates/celox-design/src/lib.rs

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tignear mentioned this pull request Oct 28, 2026

feat(sv): support the $swrite family #2403

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Comment thread crates/celox-frontend-sv/src/lowering/procedural.rs

Comment thread crates/celox/src/simulator/host/format.rs Outdated

tignear force-pushed the stack/tignear/feat/sv-uvm-string-format/support-sformatf-sformat--fe5fd5bc branch from 290e018 to 27e5a3d Compare October 28, 2026 08:40

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feat(sv): support %p for integral, string, handle and container values #2423

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