Use EI_CLASS for base ABI encoding. #47

scylaac · 2022-04-19T03:35:03Z

No description provided.

xen0n

为得各下游项目命名一致，可给 0x1 0x2 0x3 起名，例如 EF_LOONGARCH_FPABI_S EF_LOONGARCH_FPABI_F EF_LOONGARCH_FPABI_D 这样。反正 binutils 那边也必须起名。

MaskRay · 2022-04-19T04:56:13Z

docs/LoongArch-ELF-ABI-EN.adoc

-The ABI type of an ELF object is uniquely identified by `e_flags[7:0]` in its header.
+The ABI type of an ELF object is uniquely identified by `e_flags[7:0]` and `EI_CLASS` in its header.
+Within this combination, `e_flags[2:0]` and `EI_CLASS` correspond to the **base ABI** type,
+where `EI_CLASS` determines how C integral and pointer types are expressed (<<c-lang-data-model, data model>>)


The description of EI_CLASS is inaccurate.

See http://www.sco.com/developers/gabi/latest/ch4.eheader.html

这儿不是对 EI_CLASS 本身语义的描述，而是 "借用" EI_CLASS 标记龙芯架构基础 ABI 类型信息，如 ELF32 只容纳 ilp32* ABI 的程序。如果确实容易引起误解的话，应该怎么修改比较好呢？

RISC-V 那边是这么写的：

EI_CLASS
Specifies the base ISA, either RV32 or RV64. We don’t let users link RV32 and RV64 code together.

好像也有这个问题……

改成 "the expression of C integral and pointer types are uniquely determined by EI_CLASS value, we don't support LP64 ABIs with ELFCLASS32 or ILP32 ABIs with ELFCLASS64" 这样？

scylaac · 2022-04-19T07:10:09Z

为得各下游项目命名一致，可给 0x1 0x2 0x3 起名，例如 EF_LOONGARCH_FPABI_S EF_LOONGARCH_FPABI_F EF_LOONGARCH_FPABI_D 这样。反正 binutils 那边也必须起名。

这个我们再讨论一下吧... base ABI 还是一个整体，不是特别希望 e_flags[2:0] 被视为单独的 "FPABI"，否则省出这些编码空间也没有多大灵活性。😂

xen0n · 2022-04-19T07:54:58Z

为得各下游项目命名一致，可给 0x1 0x2 0x3 起名，例如 EF_LOONGARCH_FPABI_S EF_LOONGARCH_FPABI_F EF_LOONGARCH_FPABI_D 这样。反正 binutils 那边也必须起名。

这个我们再讨论一下吧... base ABI 还是一个整体，不是特别希望 e_flags[2:0] 被视为单独的 "FPABI"，否则省出这些编码空间也没有多大灵活性。:joy:

这可能就是个取名问题，不希望被理解成 FPABI 的话，那我觉得叫 FPABI_MARKER 之类一眼能看出来不是独立组成部分的名字就好了。

SixWeining · 2022-07-22T02:59:06Z

docs/LoongArch-ELF-ABI-EN.adoc


 [%header,cols="1,1,1,1"]
 |====
 | Bit 31 - 8 | Bit 7 - 6   | Bit 5 - 3      | Bit 2 - 0
-| (reserved) | ABI version | ABI extension  | Base ABI
+| (reserved) | ABI version | ABI extension  | Base ABI (partial)


I think we should give bits[2-0] a better name. Something like 'FP ABI Maker' as @xen0n proposed can be considered?

scylaac · 2022-07-25T02:44:43Z

感谢提议，要不我们改叫 Base ABI Modifier 吧。

…rchTargetStreamer Reference: https://github.com/loongson/LoongArch-Documentation The last commit hash (main branch) is: 99016636af64d02dee05e39974d4c1e55875c45b Note: There are several PRs [1][2][3] that may affect the e_flags. After they got closed or merged, we should update the implementation here accordingly. [1] loongson/LoongArch-Documentation#33 [2] loongson/LoongArch-Documentation#47 [2] loongson/LoongArch-Documentation#61 Differential Revision: https://reviews.llvm.org/D130239

ChenghuaXu

Ok.

xen0n · 2022-08-16T07:20:10Z

起一下 ELF 常量名字？Base ABI Modifier，EF_LOONGARCH_ABIMOD_{S,F,D}? 感觉和一切带 LoongArch 全称的名字一样，太长了。。叫 EF_LOONGARCH_BASE_ABI_MODIFIER_xx 是断然不可接受的，叫 EF_LOONGARCH_BAM_xx 又太晦涩。

ChenghuaXu · 2022-08-16T07:37:42Z

起一下 ELF 常量名字？Base ABI Modifier，EF_LOONGARCH_ABIMOD_{S,F,D}? 感觉和一切带 LoongArch 全称的名字一样，太长了。。叫 EF_LOONGARCH_BASE_ABI_MODIFIER_xx 是断然不可接受的，叫 EF_LOONGARCH_BAM_xx 又太晦涩。
ABI Modifier指位域名称。里面的枚举值简单一些EF_LARCH_S/F/D?

xen0n · 2022-08-16T07:58:57Z

起一下 ELF 常量名字？Base ABI Modifier，EF_LOONGARCH_ABIMOD_{S,F,D}? 感觉和一切带 LoongArch 全称的名字一样，太长了。。叫 EF_LOONGARCH_BASE_ABI_MODIFIER_xx 是断然不可接受的，叫 EF_LOONGARCH_BAM_xx 又太晦涩。
ABI Modifier指位域名称。里面的枚举值简单一些EF_LARCH_S/F/D?

现在是叫 EF_LOONGARCH_xxx 的。

/* Processor specific flags for the ELF header e_flags field.  */
/*The flag lp64s/lp64f/lp64d/ilp32s/ilp32f/ilp32d 3bits. */
#define EF_LOONGARCH_ABI_LP64_SOFT_FLOAT        0x1
#define EF_LOONGARCH_ABI_LP64_SINGLE_FLOAT      0x2
#define EF_LOONGARCH_ABI_LP64_DOUBLE_FLOAT      0x3

#define EF_LOONGARCH_ABI_ILP32_SOFT_FLOAT       0x5
#define EF_LOONGARCH_ABI_ILP32_SINGLE_FLOAT     0x6
#define EF_LOONGARCH_ABI_ILP32_DOUBLE_FLOAT     0x7

#define EF_LOONGARCH_ABI_MASK                   0x7
#define EF_LOONGARCH_ABI_ILP32_MASK             0x4
#define EF_LOONGARCH_ABI_FLOAT_MASK             0x3
#define EF_LOONGARCH_ABI_SOFT_FLOAT_MASK        0x1
#define EF_LOONGARCH_ABI_SINGLE_FLOAT_MASK      0x2
#define EF_LOONGARCH_ABI_DOUBLE_FLOAT_MASK      0x3

#define EF_LOONGARCH_ABI(abi)   (EF_LOONGARCH_ABI_MASK & (abi))

#define EF_LOONGARCH_IS_LP64(abi) \
  (EF_LOONGARCH_ABI(abi) && (!(EF_LOONGARCH_ABI(abi) & EF_LOONGARCH_ABI_ILP32_MASK)))
#define EF_LOONGARCH_IS_ILP32(abi) \
  (EF_LOONGARCH_ABI(abi) && (EF_LOONGARCH_ABI(abi) & EF_LOONGARCH_ABI_ILP32_MASK))

#define EF_LOONGARCH_IS_SOFT_FLOAT(abi) \
  (!((EF_LOONGARCH_ABI(abi) & EF_LOONGARCH_ABI_FLOAT_MASK) ^ EF_LOONGARCH_ABI_SOFT_FLOAT_MASK))

#define EF_LOONGARCH_IS_SINGLE_FLOAT(abi) \
  (!((EF_LOONGARCH_ABI(abi) & EF_LOONGARCH_ABI_FLOAT_MASK) ^ EF_LOONGARCH_ABI_SINGLE_FLOAT_MASK))

#define EF_LOONGARCH_IS_DOUBLE_FLOAT(abi) \
  (!((EF_LOONGARCH_ABI(abi) & EF_LOONGARCH_ABI_FLOAT_MASK) ^ EF_LOONGARCH_ABI_DOUBLE_FLOAT_MASK))

那叫 EF_LOONGARCH_ABI_{S,F,D} 其实就好了？或者仍然保留 xxx_ABI_SOFT_FLOAT 这样的较长的形式，改动相对更小。别的定义也相应微调一下就好。

xen0n · 2022-08-16T08:03:02Z

/* Processor specific flags for the ELF header e_flags field.  */
/* Base ABI modifier, 3bits. */
#define EF_LOONGARCH_ABI_SOFT_FLOAT        0x1
#define EF_LOONGARCH_ABI_SINGLE_FLOAT      0x2
#define EF_LOONGARCH_ABI_DOUBLE_FLOAT      0x3
#define EF_LOONGARCH_ABI_MODIFIER_MASK     0x7
#define EF_LOONGARCH_ABI_MODIFIER(abi)     (EF_LOONGARCH_ABI_MODIFIER_MASK & (abi))

#define EF_LOONGARCH_IS_SOFT_FLOAT(abi) \
  (EF_LOONGARCH_ABI_MODIFIER(abi) == EF_LOONGARCH_ABI_SOFT_FLOAT)

#define EF_LOONGARCH_IS_SINGLE_FLOAT(abi) \
  (EF_LOONGARCH_ABI_MODIFIER(abi) == EF_LOONGARCH_ABI_SINGLE_FLOAT)

#define EF_LOONGARCH_IS_DOUBLE_FLOAT(abi) \
  (EF_LOONGARCH_ABI_MODIFIER(abi) == EF_LOONGARCH_ABI_DOUBLE_FLOAT)

ChenghuaXu · 2022-08-17T03:20:37Z

文档是不是可以合了，至于代码中如何改可以参考这个。

/* Processor specific flags for the ELF header e_flags field.  */
/* Base ABI modifier, 3bits. */
#define EF_LOONGARCH_ABI_SOFT_FLOAT        0x1
#define EF_LOONGARCH_ABI_SINGLE_FLOAT      0x2
#define EF_LOONGARCH_ABI_DOUBLE_FLOAT      0x3
#define EF_LOONGARCH_ABI_MODIFIER_MASK     0x7
#define EF_LOONGARCH_ABI_MODIFIER(abi)     (EF_LOONGARCH_ABI_MODIFIER_MASK & (abi))

#define EF_LOONGARCH_IS_SOFT_FLOAT(abi) \
  (EF_LOONGARCH_ABI_MODIFIER(abi) == EF_LOONGARCH_ABI_SOFT_FLOAT)

#define EF_LOONGARCH_IS_SINGLE_FLOAT(abi) \
  (EF_LOONGARCH_ABI_MODIFIER(abi) == EF_LOONGARCH_ABI_SINGLE_FLOAT)

#define EF_LOONGARCH_IS_DOUBLE_FLOAT(abi) \
  (EF_LOONGARCH_ABI_MODIFIER(abi) == EF_LOONGARCH_ABI_DOUBLE_FLOAT)

yetist

LGTM

…rchTargetStreamer Reference: https://github.com/loongson/LoongArch-Documentation The last commit hash (main branch) is: 99016636af64d02dee05e39974d4c1e55875c45b Note: There are several PRs [1][2][3] that may affect the e_flags. After they got closed or merged, we should update the implementation here accordingly. [1] loongson/LoongArch-Documentation#33 [2] loongson/LoongArch-Documentation#47 [2] loongson/LoongArch-Documentation#61 Differential Revision: https://reviews.llvm.org/D130239

Update handling of e_flags according to the documentation update [1] (discussions [2][3]). Object file bitness is now represented in the EI_CLASS byte. The e_flags field is now interpreted as follows: e_flags[2:0]: Base ABI modifier - 0x1: soft-float - 0x2: single-precision hard-float - 0x3: double-precision hard-float e_flags[7:6]: ELF object ABI version - 0x0: v0 - 0x1: v1 [1]: https://github.com/loongson/LoongArch-Documentation/blob/main/docs/LoongArch-ELF-ABI-EN.adoc#e_flags-identifies-abi-type-and-version [2]: loongson/LoongArch-Documentation#61 [3]: loongson/LoongArch-Documentation#47

Update handling of e_flags according to the documentation update [1] (discussions [2][3]). Object file bitness is now represented in the EI_CLASS byte. The e_flags field is now interpreted as follows: e_flags[2:0]: Base ABI modifier - 0x1: soft-float - 0x2: single-precision hard-float - 0x3: double-precision hard-float e_flags[7:6]: ELF object ABI version - 0x0: v0 - 0x1: v1 [1]: https://github.com/loongson/LoongArch-Documentation/blob/main/docs/LoongArch-ELF-ABI-EN.adoc#e_flags-identifies-abi-type-and-version [2]: loongson/LoongArch-Documentation#61 [3]: loongson/LoongArch-Documentation#47 (cherry picked from commit c4a7e6b)

scylaac requested review from lzshhxx, FreeFlyingSheep and ChenghuaXu April 19, 2022 03:35

xen0n reviewed Apr 19, 2022

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MaskRay reviewed Apr 19, 2022

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Use EI_CLASS for base ABI encoding.

4da1932

scylaac force-pushed the simplify-eflags branch from 2bca885 to 4da1932 Compare April 20, 2022 09:17

SixWeining reviewed Jul 22, 2022

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Refer to e_flags[2:0] as the "base ABI modifier".

7720b73

scylaac requested a review from SixWeining July 27, 2022 01:59

SixWeining mentioned this pull request Aug 10, 2022

LoongArch:docs: Update e_flags for new relocations. #61

Merged

ChenghuaXu approved these changes Aug 16, 2022

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ChenghuaXu requested a review from chenglulu326 August 17, 2022 03:21

lzshhxx approved these changes Aug 17, 2022

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ChenghuaXu requested a review from yetist August 17, 2022 03:23

lzshhxx approved these changes Aug 17, 2022

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SixWeining approved these changes Aug 17, 2022

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yetist approved these changes Aug 17, 2022

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FreeFlyingSheep merged commit 6c49901 into loongson:main Aug 17, 2022

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Use EI_CLASS for base ABI encoding. #47

Use EI_CLASS for base ABI encoding. #47

scylaac commented Apr 19, 2022

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Use EI_CLASS for base ABI encoding. #47

Use EI_CLASS for base ABI encoding. #47

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