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Oct 5, 2024

tgross35 added a commit to tgross35/rust that referenced this pull request

Nov 5, 2024

…rkingjubilee

Support clobber_abi and vector registers (clobber-only) in PowerPC inline assembly

This supports clobber_abi which is one of the requirements of stabilization mentioned in rust-lang#93335.

This basically does a similar thing I did in rust-lang#130630 to implement clobber_abi for s390x, but for powerpc/powerpc64/powerpc64le.

This also supports vector registers (as vreg) as clobber-only, which need to support clobbering of them to implement clobber_abi.
vreg should be able to accept #[repr(simd)] types as input/output if the unstable altivec target feature is enabled, but core::arch::{powerpc,powerpc64} vector types, #[repr(simd)], and core::simd are all unstable, so the fact that this is currently a clobber-only should not be considered a blocker of clobber_abi implementation or stabilization. So I have not implemented it in this PR.
- See rust-lang#131551 (which is based on this PR) for a PR to implement this.
- (I'm not sticking to whether that PR should be a separate PR or part of this PR, so I can merge that PR into this PR if needed.)

Refs:

PPC32 SysV: Section "Function Calling Sequence" in System V Application Binary Interface PowerPC Processor Supplement
PPC64 ELFv1: Section 3.2 "Function Calling Sequence" in 64-bit PowerPC ELF Application Binary Interface Supplement
PPC64 ELFv2: Section 2.2 "Function Calling Sequence" in 64-Bit ELF V2 ABI Specification
AIX: Register usage and conventions, Special registers in the PowerPC®, AIX vector programming
Register definition in LLVM: https://github.com/llvm/llvm-project/blob/llvmorg-19.1.0/llvm/lib/Target/PowerPC/PPCRegisterInfo.td#L189

If I understand the above four ABI documentations correctly, except for the PPC32 SysV's VR (Vector Registers) and 32-bit AIX (currently not supported by rustc)'s r13, there does not appear to be important differences in terms of implementing clobber_abi:

The above four ABIs are consistent about FPR (0-13: volatile, 14-31: nonvolatile), CR (0-1,5-7: volatile, 2-4: nonvolatile), XER (volatile), and CTR (volatile).
As for GPR, only the registers we are treating as reserved are slightly different
- r0, r3-r12 are volatile
- r1(sp, reserved), r14-31 are nonvolatile
- r2(reserved) is TOC pointer in PPC64 ELF/AIX, system-reserved register in PPC32 SysV (AFAIK used as thread pointer in Linux/BSDs)
- r13(reserved for non-32-bit-AIX) is thread pointer in PPC64 ELF, small data area pointer register in PPC32 SysV, "reserved under 64-bit environment; not restored across system calls[^r13]" in AIX)
As for FPSCR, volatile in PPC64 ELFv1/AIX, some fields are volatile only in certain situations (rest are volatile) in PPC32 SysV/PPC64 ELFv2.
As for VR (Vector Registers), it is not mentioned in PPC32 SysV, v0-v19 are volatile in both in PPC64 ELF/AIX, v20-v31 are nonvolatile in PPC64 ELF, reserved or nonvolatile depending on the ABI (vec-extabi vs vec-default in LLVM, we are [using vec-extabi](rust-lang#131341 (comment))) in AIX:

When the default Vector enabled mode is used, these registers are reserved and must not be used. In the extended ABI vector enabled mode, these registers are nonvolatile and their values are preserved across function calls

I left [FIXME comment about PPC32 SysV](rust-lang#131341 (comment)) and added ABI check for AIX.
As for VRSAVE, it is not mentioned in PPC32 SysV, nonvolatile in PPC64 ELFv1, reserved in PPC64 ELFv2/AIX
As for VSCR, it is not mentioned in PPC32 SysV/PPC64 ELFv1, some fields are volatile only in certain situations (rest are volatile) in PPC64 ELFv2, volatile in AIX

We are currently treating r1-r2, r13 (non-32-bit-AIX), r29-r31, LR, CTR, and VRSAVE as reserved. We are currently not processing anything about FPSCR and VSCR, but I feel those are things that should be processed by preserves_flags rather than clobber_abi if we need to do something about them. (However, PPCRegisterInfo.td in LLVM does not seem to define anything about them.)

Replaces rust-lang#111335 and rust-lang#124279

cc @ecnelises @bzEq @lu-zero

r? @Amanieu

@rustbot label +O-PowerPC +A-inline-assembly

[^r13]: callee-saved, according to LLVM and GCC.

bors added a commit to rust-lang-ci/rust that referenced this pull request

Nov 5, 2024

…ingjubilee

Support clobber_abi and vector registers (clobber-only) in PowerPC inline assembly

This supports clobber_abi which is one of the requirements of stabilization mentioned in rust-lang#93335.

This basically does a similar thing I did in rust-lang#130630 to implement clobber_abi for s390x, but for powerpc/powerpc64/powerpc64le.

This also supports vector registers (as vreg) as clobber-only, which need to support clobbering of them to implement clobber_abi.
vreg should be able to accept #[repr(simd)] types as input/output if the unstable altivec target feature is enabled, but core::arch::{powerpc,powerpc64} vector types, #[repr(simd)], and core::simd are all unstable, so the fact that this is currently a clobber-only should not be considered a blocker of clobber_abi implementation or stabilization. So I have not implemented it in this PR.
- See rust-lang#131551 (which is based on this PR) for a PR to implement this.
- (I'm not sticking to whether that PR should be a separate PR or part of this PR, so I can merge that PR into this PR if needed.)

Refs:

PPC32 SysV: Section "Function Calling Sequence" in System V Application Binary Interface PowerPC Processor Supplement
PPC64 ELFv1: Section 3.2 "Function Calling Sequence" in 64-bit PowerPC ELF Application Binary Interface Supplement
PPC64 ELFv2: Section 2.2 "Function Calling Sequence" in 64-Bit ELF V2 ABI Specification
AIX: Register usage and conventions, Special registers in the PowerPC®, AIX vector programming
Register definition in LLVM: https://github.com/llvm/llvm-project/blob/llvmorg-19.1.0/llvm/lib/Target/PowerPC/PPCRegisterInfo.td#L189

The above four ABIs are consistent about FPR (0-13: volatile, 14-31: nonvolatile), CR (0-1,5-7: volatile, 2-4: nonvolatile), XER (volatile), and CTR (volatile).
As for GPR, only the registers we are treating as reserved are slightly different
- r0, r3-r12 are volatile
- r1(sp, reserved), r14-31 are nonvolatile
- r2(reserved) is TOC pointer in PPC64 ELF/AIX, system-reserved register in PPC32 SysV (AFAIK used as thread pointer in Linux/BSDs)
- r13(reserved for non-32-bit-AIX) is thread pointer in PPC64 ELF, small data area pointer register in PPC32 SysV, "reserved under 64-bit environment; not restored across system calls[^r13]" in AIX)
As for FPSCR, volatile in PPC64 ELFv1/AIX, some fields are volatile only in certain situations (rest are volatile) in PPC32 SysV/PPC64 ELFv2.
As for VR (Vector Registers), it is not mentioned in PPC32 SysV, v0-v19 are volatile in both in PPC64 ELF/AIX, v20-v31 are nonvolatile in PPC64 ELF, reserved or nonvolatile depending on the ABI (vec-extabi vs vec-default in LLVM, we are [using vec-extabi](rust-lang#131341 (comment))) in AIX:

When the default Vector enabled mode is used, these registers are reserved and must not be used. In the extended ABI vector enabled mode, these registers are nonvolatile and their values are preserved across function calls

I left [FIXME comment about PPC32 SysV](rust-lang#131341 (comment)) and added ABI check for AIX.
As for VRSAVE, it is not mentioned in PPC32 SysV, nonvolatile in PPC64 ELFv1, reserved in PPC64 ELFv2/AIX
As for VSCR, it is not mentioned in PPC32 SysV/PPC64 ELFv1, some fields are volatile only in certain situations (rest are volatile) in PPC64 ELFv2, volatile in AIX

Replaces rust-lang#111335 and rust-lang#124279

cc @ecnelises @bzEq @lu-zero

r? @Amanieu

@rustbot label +O-PowerPC +A-inline-assembly

[^r13]: callee-saved, according to LLVM and GCC.

antoyo pushed a commit to antoyo/rust that referenced this pull request

Jan 13, 2025

…ingjubilee

Support clobber_abi and vector registers (clobber-only) in PowerPC inline assembly

This supports clobber_abi which is one of the requirements of stabilization mentioned in rust-lang#93335.

This basically does a similar thing I did in rust-lang#130630 to implement clobber_abi for s390x, but for powerpc/powerpc64/powerpc64le.

This also supports vector registers (as vreg) as clobber-only, which need to support clobbering of them to implement clobber_abi.
vreg should be able to accept #[repr(simd)] types as input/output if the unstable altivec target feature is enabled, but core::arch::{powerpc,powerpc64} vector types, #[repr(simd)], and core::simd are all unstable, so the fact that this is currently a clobber-only should not be considered a blocker of clobber_abi implementation or stabilization. So I have not implemented it in this PR.
- See rust-lang#131551 (which is based on this PR) for a PR to implement this.
- (I'm not sticking to whether that PR should be a separate PR or part of this PR, so I can merge that PR into this PR if needed.)

Refs:

PPC32 SysV: Section "Function Calling Sequence" in System V Application Binary Interface PowerPC Processor Supplement
PPC64 ELFv1: Section 3.2 "Function Calling Sequence" in 64-bit PowerPC ELF Application Binary Interface Supplement
PPC64 ELFv2: Section 2.2 "Function Calling Sequence" in 64-Bit ELF V2 ABI Specification
AIX: Register usage and conventions, Special registers in the PowerPC®, AIX vector programming
Register definition in LLVM: https://github.com/llvm/llvm-project/blob/llvmorg-19.1.0/llvm/lib/Target/PowerPC/PPCRegisterInfo.td#L189

The above four ABIs are consistent about FPR (0-13: volatile, 14-31: nonvolatile), CR (0-1,5-7: volatile, 2-4: nonvolatile), XER (volatile), and CTR (volatile).
As for GPR, only the registers we are treating as reserved are slightly different
- r0, r3-r12 are volatile
- r1(sp, reserved), r14-31 are nonvolatile
- r2(reserved) is TOC pointer in PPC64 ELF/AIX, system-reserved register in PPC32 SysV (AFAIK used as thread pointer in Linux/BSDs)
- r13(reserved for non-32-bit-AIX) is thread pointer in PPC64 ELF, small data area pointer register in PPC32 SysV, "reserved under 64-bit environment; not restored across system calls[^r13]" in AIX)
As for FPSCR, volatile in PPC64 ELFv1/AIX, some fields are volatile only in certain situations (rest are volatile) in PPC32 SysV/PPC64 ELFv2.
As for VR (Vector Registers), it is not mentioned in PPC32 SysV, v0-v19 are volatile in both in PPC64 ELF/AIX, v20-v31 are nonvolatile in PPC64 ELF, reserved or nonvolatile depending on the ABI (vec-extabi vs vec-default in LLVM, we are [using vec-extabi](rust-lang#131341 (comment))) in AIX:

When the default Vector enabled mode is used, these registers are reserved and must not be used. In the extended ABI vector enabled mode, these registers are nonvolatile and their values are preserved across function calls

I left [FIXME comment about PPC32 SysV](rust-lang#131341 (comment)) and added ABI check for AIX.
As for VRSAVE, it is not mentioned in PPC32 SysV, nonvolatile in PPC64 ELFv1, reserved in PPC64 ELFv2/AIX
As for VSCR, it is not mentioned in PPC32 SysV/PPC64 ELFv1, some fields are volatile only in certain situations (rest are volatile) in PPC64 ELFv2, volatile in AIX

Replaces rust-lang#111335 and rust-lang#124279

cc @ecnelises @bzEq @lu-zero

r? @Amanieu

@rustbot label +O-PowerPC +A-inline-assembly

[^r13]: callee-saved, according to LLVM and GCC.