Clarify the new toolchain conventions revision.

docs/LoongArch-toolchain-conventions-CN.adoc

@@ -1,6 +1,6 @@
 = 龙芯架构工具链约定
 龙芯中科技术股份有限公司
-v1.00
+v2.00
 :docinfodir: ../themes
 :docinfo: shared
 :doctype: book
@@ -290,6 +290,18 @@ ABI 配置的需要。若不能，则应根据下表，在默认可用指令集
 基础 ABI 的浮点部分和 ABI 扩展特性则分别由连续附加在 multiarch 标识符
 `os` 字段后的两个字符串后缀 (`<fabi_suffix><abiext_suffix>`) 标记。
 
+本《约定》的 1.00 版本曾规定了基础 ABI 使用 64 位浮点寄存器传参时的
+`<fabi_suffix>` 后缀为 `f64` （意味着类似 `loongarch64-linux-gnuf64` 的
+multiarch 架构标识符取值）。
+2.00 版本起将其改为空字符串，是考虑到最常见的组合适合尽量短的名字，
+因此不介意文本上的不兼容变更。
+为尽可能维持向后兼容，应在见到 `gnuf64` 这一目标元组环境字段取值时，
+将其视为（标准化为） `gnu` 如果这样做因不会带来其他超越近处业务逻辑的外部副作用而可行。
+（例如：如果维持对 `gnuf64` 的兼容性涉及必须添加符号链接或复制文件，
+从而不得不产生文件系统、目录结构等方面的副作用，那么就不再视这样代价的兼容为“可行”。
+一个具体实例是 Python 的原生扩展 `.so` 文件带且只能带唯一的 multiarch 架构标识符，
+此时便无法做到兼容本《约定》的 v1.00 了。）
+
 .Multiarch `os` 字段，`<fabi_suffix>` 后缀标记及其含义
 [%header,cols="^1,^2"]
 |===
@@ -512,3 +524,15 @@ LoongArch 平台特有的预处理器内建宏。下表列举了这些架构相
 |`\\__SIZEOF_POINTER__` 乘以 8
 |（无）
 |===
+
+== 附录：版本修订历史
+
+- **v1.00**
+
+    * 初始版本。
+
+- **v2.00**
+
+    * 不兼容地修订 multiarch 架构标识符的相关内容：
+    ** 移除为 ILP32 ABIs 预留的 multiarch 架构标识符。
+    ** 修改浮点 ABI 后缀 `f64` 为空值。

docs/LoongArch-toolchain-conventions-EN.adoc

@@ -1,6 +1,6 @@
 = LoongArch Toolchain Conventions
 Loongson Technology Corporation Limited
-v1.00
+v2.00
 :docinfodir: ../themes
 :docinfo: shared
 :doctype: book
@@ -331,6 +331,23 @@ the floating-point base ABI and the ABI extension type are encoded
 with two string suffices (`<fabi-suffix><abiext-suffix>`) to the `os` field of the
 specifier, respectively.
 
+Version 1.00 of this document mandated that a `<fabi-suffix>` of `f64` shall
+be used for cases where the base ABI used 64-bit FPRs for parameter passing
+(meaning multiarch architecture specifier values resembling `loongarch64-linux-gnuf64`).
+From version 2.00 onwards it was changed into the empty string;
+the incompatible textual change is justified by the rationale that shorter
+names are preferred for the more ubiquitous combinations.
+For maintaining best-effort backwards compatibility, the target tuple environment
+value `gnuf64` shall be treated as (canonicalized into) `gnu` if doing so
+would be feasible by not bringing any external side effects that goes beyond
+the local domain-specific logic (aka "business logic").
+(For example: if one must symlink and/or copy files to maintain compatibility
+with `gnuf64`, incurring necessary side effects at the filesystem / directory
+layout level, then the compatibility would be deemed too costly to be "feasible".
+A concrete case would be Python, whose native extensions' file names contain
+exactly one multiarch architecture specifier. In this case there is unfortunately
+no way to accommodate v1.00 of this document.)
+
 .List of possible `<fabi-suffix>`
 [%header,cols="^1,^2"]
 |===
@@ -555,3 +572,15 @@ portable code should not assume existence of these macros, nor use them.
 |`\\__SIZEOF_POINTER__` multiplied by 8
 |n/a
 |===
+
+== Appendix: Revision History
+
+- **v1.00**
+
+    * Initial version of the specification.
+
+- **v2.00**
+
+    * Incompatibly revise the multiarch architecture specifiers:
+    ** Remove multiarch architecture specifiers reserved for the ILP32 ABIs.
+    ** Change the floating-point ABI suffix `f64` into the empty string.