cmd/internal/obj/riscv: add assembly support of Zfa extension by lxq015 · Pull Request #76996 · golang/go

lxq015 · 2025-12-26T08:30:52Z

This patch adds the assembly support of Zfa extension, which is defined
in chapter 26 of RISC-V ISA manual.

Zfa adds several additional floating-point instructions and is mandatory
in RVA23 profile.

Follow-up to CL 631575

Co-authored-by: wangpengcheng.pp@bytedance.com

gopherbot · 2025-12-26T08:36:56Z

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gopherbot · 2025-12-26T08:44:55Z

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Patch Set 1:

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gopherbot · 2025-12-26T09:08:52Z

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Patch Set 2:

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gopherbot · 2025-12-27T06:56:16Z

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Patch Set 3:

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gopherbot · 2026-03-27T01:21:59Z

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Patch Set 3:

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gopherbot · 2026-05-22T12:13:33Z

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Patch Set 3:

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gopherbot · 2026-05-26T01:25:37Z

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gopherbot · 2026-05-26T01:53:20Z

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Patch Set 4:

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gopherbot · 2026-06-22T09:06:16Z

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Patch Set 4: Code-Review+2 Commit-Queue+1

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gopherbot · 2026-06-22T09:06:16Z

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Patch Set 4:

Dry run: CV is trying the patch.

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gopherbot · 2026-06-22T09:06:17Z

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Patch Set 4: -Commit-Queue

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gopherbot · 2026-06-22T09:06:18Z

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Patch Set 4:

This CL has failed the run. Reason:

Tryjob golang/try/x_tools-gotip-linux-amd64 has failed with summary (view all results):

go on master (change 732700) / tools on master (commit 216d7a7)

Error: Failed to run "fetch \"golang.org/x/tools/gopls\" dependencies": exit status 1

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gopherbot · 2026-06-22T09:06:18Z

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Patch Set 4: LUCI-TryBot-Result-1

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gopherbot · 2026-09-28T03:49:56Z

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gopherbot · 2026-09-28T10:12:14Z

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Patch Set 5: Commit-Queue+1

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gopherbot · 2026-09-28T10:12:15Z

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Patch Set 5:

Dry run: CV is trying the patch.

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gopherbot · 2026-09-28T10:34:25Z

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Patch Set 5: -Commit-Queue

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gopherbot · 2026-09-28T10:34:25Z

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Patch Set 5:

This CL has failed the run. Reason:

Tryjob golang/try/gotip-linux-arm64_debian13 has failed with summary (view all results):

go on master (change 732700)

To reproduce, try gomote repro 8669425104989874593.

Additional links for debugging:

go tool dist test -json output [shard 4]

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gopherbot · 2026-09-28T10:34:26Z

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Patch Set 5: LUCI-TryBot-Result-1

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gopherbot · 2026-10-02T15:09:27Z

Message from Julian Zhu:

Patch Set 5:

(4 comments)

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…ouble The single fimmMapping keyed by float64 served both FLIS (single-precision immediate) and FLID (double-precision immediate), which made progedit and the encoder disagree: progedit looked up float64(f32) (the operand rounded to float32 then widened back) while the encoder looked up the original float64 operand. A double like 1.0000000000000002 rounds to 1.0 as float32 and would pass progedit's check but fail the encoder's, producing an "unknown floating point immediate" error. Split the map into flisMapping (float32 keys) and flidMapping (float64 keys), and check each instruction in its own domain: FLIS keys on the float32 value, FLID on the float64 value. Also check NaN on float32 directly (f32 != f32) since math.IsNaN only accepts float64.

flidMapping[1] was copied from flisMapping and held the single-precision minimum positive normal (2^-126, 1.1754943508222875e-38). Per the RISC-V Zfa spec, entry 1 (the minimum positive normal value) has a numerically different value for double-precision, so flidMapping[1] must be the double-precision minimum positive normal 2^-1022 (2.2250738585072014e-308). Update the corresponding FLID test line in riscv64.s to use the double value; its encoding (index 1) is unchanged.

The Zfa fround/froundnx instructions take an explicit rounding mode in the rm field (bits 14:12), but AFROUNDS/AFROUNDNXS/AFROUNDD/AFROUNDNXD were only given rFFEncoding, which hardcoded funct3 to 0 (RNE) with no way to select another rounding mode. Wire them into the existing rounding-mode suffix mechanism used by fcvt: ParseSuffix now accepts .RNE/.RTZ/.RDN/.RUP/.RMM on the fround instructions and stores the mode in Scond, and instructionsForProg writes it into funct3, defaulting to RNE when no suffix is given (preserving the previous encoding for suffix-free fround). Add end-to-end tests for all four fround instructions across all five rounding modes.

gopherbot · 2026-10-10T07:26:50Z

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gopherbot · 2026-10-10T08:07:52Z

Message from Xueqi Luo:

Patch Set 6:

(5 comments)

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hbrooks mentioned this pull request May 28, 2026

cmd/internal/obj/riscv: add assembly support of Zfa extension ellipsis-dev-test/go#11

Open

lxq015 force-pushed the zfa_asm branch from ef6f524 to faa5743 Compare September 28, 2026 03:44

lxq015 added 7 commits October 10, 2026 09:31

cmd/internal/obj/riscv: add assembly support of Zfa extension

b60c1ae

fix fimmMapping error

f42aec7

cmd/internal/obj/riscv: fix formatting

da7e499

cmd/internal/obj/riscv: gofmt flidMapping table alignment

fa904af

lxq015 force-pushed the zfa_asm branch from faa5743 to c661ca4 Compare October 10, 2026 07:19

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