Re: [PATCH 02/14] MIPS: Always use -Wa,-msoft-float and eliminate GAS_HAS_SET_HARDFLOAT

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On Wed, Jan 4, 2023 at 11:54 AM Nathan Chancellor <nathan@xxxxxxxxxx> wrote:
>
> -Wa,-msoft-float is tested with as-option, which will be a problem for
> clang with an upcoming change to move as-option to use KBUILD_AFLAGS
> instead of KBUILD_CFLAGS due to a lack of '-mno-abicalls' in
> KBUILD_AFLAGS at the point that this check occurs; $(cflags-y) is added
> to KBUILD_AFLAGS towards the end of this file.
>
>   clang: error: ignoring '-fno-PIE' option as it cannot be used with implicit usage of -mabicalls and the N64 ABI [-Werror,-Woption-ignored]
>
> This could be resolved by switching to a cc-option check but
> '$(cflags-y)' would need to be added so that '-mno-abicalls' is present
> for the test. However, this check is no longer necessary, as
> -msoft-float is supported by all supported assembler versions (GNU as
> 2.25+ and LLVM 11+). Eliminate GAS_HAS_SET_HARDFLOAT and all of its
> uses, inlining SET_HARDFLOAT where necessary.
>
> Link: https://lore.kernel.org/202209101939.bvk64Fok-lkp@xxxxxxxxx/
> Reported-by: kernel test robot <lkp@xxxxxxxxx>
> Signed-off-by: Nathan Chancellor <nathan@xxxxxxxxxx>

Thanks for the patch!
Reviewed-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>

> ---
> Cc: tsbogend@xxxxxxxxxxxxxxxx
> Cc: linux-mips@xxxxxxxxxxxxxxx
> ---
>  arch/mips/Makefile                  | 11 +---------
>  arch/mips/include/asm/asmmacro-32.h |  4 ++--
>  arch/mips/include/asm/asmmacro.h    | 42 ++++++++++++++++++-------------------
>  arch/mips/include/asm/fpregdef.h    | 14 -------------
>  arch/mips/include/asm/mipsregs.h    | 20 ++++--------------
>  arch/mips/kernel/genex.S            |  2 +-
>  arch/mips/kernel/r2300_fpu.S        |  4 ++--
>  arch/mips/kernel/r4k_fpu.S          | 12 +++++------
>  arch/mips/kvm/fpu.S                 |  6 +++---
>  9 files changed, 40 insertions(+), 75 deletions(-)
>
> diff --git a/arch/mips/Makefile b/arch/mips/Makefile
> index 490dea07d4e0..a00a6d94e16f 100644
> --- a/arch/mips/Makefile
> +++ b/arch/mips/Makefile
> @@ -95,7 +95,7 @@ all-$(CONFIG_SYS_SUPPORTS_ZBOOT)+= vmlinuz
>  # crossformat linking we rely on the elf2ecoff tool for format conversion.
>  #
>  cflags-y                       += -G 0 -mno-abicalls -fno-pic -pipe
> -cflags-y                       += -msoft-float
> +cflags-y                       += -msoft-float -Wa,-msoft-float
>  LDFLAGS_vmlinux                        += -G 0 -static -n -nostdlib
>  KBUILD_AFLAGS_MODULE           += -mlong-calls
>  KBUILD_CFLAGS_MODULE           += -mlong-calls
> @@ -104,15 +104,6 @@ ifeq ($(CONFIG_RELOCATABLE),y)
>  LDFLAGS_vmlinux                        += --emit-relocs
>  endif
>
> -#
> -# pass -msoft-float to GAS if it supports it.  However on newer binutils
> -# (specifically newer than 2.24.51.20140728) we then also need to explicitly
> -# set ".set hardfloat" in all files which manipulate floating point registers.
> -#
> -ifneq ($(call as-option,-Wa$(comma)-msoft-float,),)
> -       cflags-y                += -DGAS_HAS_SET_HARDFLOAT -Wa,-msoft-float
> -endif
> -
>  cflags-y += -ffreestanding
>
>  cflags-$(CONFIG_CPU_BIG_ENDIAN)                += -EB
> diff --git a/arch/mips/include/asm/asmmacro-32.h b/arch/mips/include/asm/asmmacro-32.h
> index 1c08c1f7903c..83a4940b7c89 100644
> --- a/arch/mips/include/asm/asmmacro-32.h
> +++ b/arch/mips/include/asm/asmmacro-32.h
> @@ -15,7 +15,7 @@
>
>         .macro  fpu_save_single thread tmp=t0
>         .set push
> -       SET_HARDFLOAT
> +       .set hardfloat
>         cfc1    \tmp,  fcr31
>         s.d     $f0,  THREAD_FPR0(\thread)
>         s.d     $f2,  THREAD_FPR2(\thread)
> @@ -39,7 +39,7 @@
>
>         .macro  fpu_restore_single thread tmp=t0
>         .set push
> -       SET_HARDFLOAT
> +       .set hardfloat
>         lw      \tmp, THREAD_FCR31(\thread)
>         l.d     $f0,  THREAD_FPR0(\thread)
>         l.d     $f2,  THREAD_FPR2(\thread)
> diff --git a/arch/mips/include/asm/asmmacro.h b/arch/mips/include/asm/asmmacro.h
> index ca83ada7015f..1c4438f3f2ab 100644
> --- a/arch/mips/include/asm/asmmacro.h
> +++ b/arch/mips/include/asm/asmmacro.h
> @@ -83,7 +83,7 @@
>
>         .macro  fpu_save_16even thread tmp=t0
>         .set    push
> -       SET_HARDFLOAT
> +       .set    hardfloat
>         cfc1    \tmp, fcr31
>         sdc1    $f0,  THREAD_FPR0(\thread)
>         sdc1    $f2,  THREAD_FPR2(\thread)
> @@ -109,7 +109,7 @@
>         .set    push
>         .set    mips64r2
>         .set    fp=64
> -       SET_HARDFLOAT
> +       .set    hardfloat
>         sdc1    $f1,  THREAD_FPR1(\thread)
>         sdc1    $f3,  THREAD_FPR3(\thread)
>         sdc1    $f5,  THREAD_FPR5(\thread)
> @@ -142,7 +142,7 @@
>
>         .macro  fpu_restore_16even thread tmp=t0
>         .set    push
> -       SET_HARDFLOAT
> +       .set    hardfloat
>         lw      \tmp, THREAD_FCR31(\thread)
>         ldc1    $f0,  THREAD_FPR0(\thread)
>         ldc1    $f2,  THREAD_FPR2(\thread)
> @@ -168,7 +168,7 @@
>         .set    push
>         .set    mips64r2
>         .set    fp=64
> -       SET_HARDFLOAT
> +       .set    hardfloat
>         ldc1    $f1,  THREAD_FPR1(\thread)
>         ldc1    $f3,  THREAD_FPR3(\thread)
>         ldc1    $f5,  THREAD_FPR5(\thread)
> @@ -373,7 +373,7 @@
>         .macro  _cfcmsa rd, cs
>         .set    push
>         .set    noat
> -       SET_HARDFLOAT
> +       .set    hardfloat
>         insn_if_mips 0x787e0059 | (\cs << 11)
>         insn32_if_mm 0x587e0056 | (\cs << 11)
>         move    \rd, $1
> @@ -383,7 +383,7 @@
>         .macro  _ctcmsa cd, rs
>         .set    push
>         .set    noat
> -       SET_HARDFLOAT
> +       .set    hardfloat
>         move    $1, \rs
>         insn_if_mips 0x783e0819 | (\cd << 6)
>         insn32_if_mm 0x583e0816 | (\cd << 6)
> @@ -393,7 +393,7 @@
>         .macro  ld_b    wd, off, base
>         .set    push
>         .set    noat
> -       SET_HARDFLOAT
> +       .set    hardfloat
>         PTR_ADDU $1, \base, \off
>         insn_if_mips 0x78000820 | (\wd << 6)
>         insn32_if_mm 0x58000807 | (\wd << 6)
> @@ -403,7 +403,7 @@
>         .macro  ld_h    wd, off, base
>         .set    push
>         .set    noat
> -       SET_HARDFLOAT
> +       .set    hardfloat
>         PTR_ADDU $1, \base, \off
>         insn_if_mips 0x78000821 | (\wd << 6)
>         insn32_if_mm 0x58000817 | (\wd << 6)
> @@ -413,7 +413,7 @@
>         .macro  ld_w    wd, off, base
>         .set    push
>         .set    noat
> -       SET_HARDFLOAT
> +       .set    hardfloat
>         PTR_ADDU $1, \base, \off
>         insn_if_mips 0x78000822 | (\wd << 6)
>         insn32_if_mm 0x58000827 | (\wd << 6)
> @@ -423,7 +423,7 @@
>         .macro  ld_d    wd, off, base
>         .set    push
>         .set    noat
> -       SET_HARDFLOAT
> +       .set    hardfloat
>         PTR_ADDU $1, \base, \off
>         insn_if_mips 0x78000823 | (\wd << 6)
>         insn32_if_mm 0x58000837 | (\wd << 6)
> @@ -433,7 +433,7 @@
>         .macro  st_b    wd, off, base
>         .set    push
>         .set    noat
> -       SET_HARDFLOAT
> +       .set    hardfloat
>         PTR_ADDU $1, \base, \off
>         insn_if_mips 0x78000824 | (\wd << 6)
>         insn32_if_mm 0x5800080f | (\wd << 6)
> @@ -443,7 +443,7 @@
>         .macro  st_h    wd, off, base
>         .set    push
>         .set    noat
> -       SET_HARDFLOAT
> +       .set    hardfloat
>         PTR_ADDU $1, \base, \off
>         insn_if_mips 0x78000825 | (\wd << 6)
>         insn32_if_mm 0x5800081f | (\wd << 6)
> @@ -453,7 +453,7 @@
>         .macro  st_w    wd, off, base
>         .set    push
>         .set    noat
> -       SET_HARDFLOAT
> +       .set    hardfloat
>         PTR_ADDU $1, \base, \off
>         insn_if_mips 0x78000826 | (\wd << 6)
>         insn32_if_mm 0x5800082f | (\wd << 6)
> @@ -463,7 +463,7 @@
>         .macro  st_d    wd, off, base
>         .set    push
>         .set    noat
> -       SET_HARDFLOAT
> +       .set    hardfloat
>         PTR_ADDU $1, \base, \off
>         insn_if_mips 0x78000827 | (\wd << 6)
>         insn32_if_mm 0x5800083f | (\wd << 6)
> @@ -473,7 +473,7 @@
>         .macro  copy_s_w        ws, n
>         .set    push
>         .set    noat
> -       SET_HARDFLOAT
> +       .set    hardfloat
>         insn_if_mips 0x78b00059 | (\n << 16) | (\ws << 11)
>         insn32_if_mm 0x58b00056 | (\n << 16) | (\ws << 11)
>         .set    pop
> @@ -482,7 +482,7 @@
>         .macro  copy_s_d        ws, n
>         .set    push
>         .set    noat
> -       SET_HARDFLOAT
> +       .set    hardfloat
>         insn_if_mips 0x78b80059 | (\n << 16) | (\ws << 11)
>         insn32_if_mm 0x58b80056 | (\n << 16) | (\ws << 11)
>         .set    pop
> @@ -491,7 +491,7 @@
>         .macro  insert_w        wd, n
>         .set    push
>         .set    noat
> -       SET_HARDFLOAT
> +       .set    hardfloat
>         insn_if_mips 0x79300819 | (\n << 16) | (\wd << 6)
>         insn32_if_mm 0x59300816 | (\n << 16) | (\wd << 6)
>         .set    pop
> @@ -500,7 +500,7 @@
>         .macro  insert_d        wd, n
>         .set    push
>         .set    noat
> -       SET_HARDFLOAT
> +       .set    hardfloat
>         insn_if_mips 0x79380819 | (\n << 16) | (\wd << 6)
>         insn32_if_mm 0x59380816 | (\n << 16) | (\wd << 6)
>         .set    pop
> @@ -553,7 +553,7 @@
>         st_d    29, THREAD_FPR29 - FPR_BASE_OFFS, FPR_BASE
>         st_d    30, THREAD_FPR30 - FPR_BASE_OFFS, FPR_BASE
>         st_d    31, THREAD_FPR31 - FPR_BASE_OFFS, FPR_BASE
> -       SET_HARDFLOAT
> +       .set    hardfloat
>         _cfcmsa $1, MSA_CSR
>         sw      $1, THREAD_MSA_CSR(\thread)
>         .set    pop
> @@ -562,7 +562,7 @@
>         .macro  msa_restore_all thread
>         .set    push
>         .set    noat
> -       SET_HARDFLOAT
> +       .set    hardfloat
>         lw      $1, THREAD_MSA_CSR(\thread)
>         _ctcmsa MSA_CSR, $1
>  #ifdef TOOLCHAIN_SUPPORTS_MSA
> @@ -618,7 +618,7 @@
>         .macro  msa_init_all_upper
>         .set    push
>         .set    noat
> -       SET_HARDFLOAT
> +       .set    hardfloat
>         not     $1, zero
>         msa_init_upper  0
>         msa_init_upper  1
> diff --git a/arch/mips/include/asm/fpregdef.h b/arch/mips/include/asm/fpregdef.h
> index f184ba088532..429481f9028d 100644
> --- a/arch/mips/include/asm/fpregdef.h
> +++ b/arch/mips/include/asm/fpregdef.h
> @@ -14,20 +14,6 @@
>
>  #include <asm/sgidefs.h>
>
> -/*
> - * starting with binutils 2.24.51.20140729, MIPS binutils warn about mixing
> - * hardfloat and softfloat object files.  The kernel build uses soft-float by
> - * default, so we also need to pass -msoft-float along to GAS if it supports it.
> - * But this in turn causes assembler errors in files which access hardfloat
> - * registers.  We detect if GAS supports "-msoft-float" in the Makefile and
> - * explicitly put ".set hardfloat" where floating point registers are touched.
> - */
> -#ifdef GAS_HAS_SET_HARDFLOAT
> -#define SET_HARDFLOAT .set hardfloat
> -#else
> -#define SET_HARDFLOAT
> -#endif
> -
>  #if _MIPS_SIM == _MIPS_SIM_ABI32
>
>  /*
> diff --git a/arch/mips/include/asm/mipsregs.h b/arch/mips/include/asm/mipsregs.h
> index 99eeafe6dcab..2d53704d9f24 100644
> --- a/arch/mips/include/asm/mipsregs.h
> +++ b/arch/mips/include/asm/mipsregs.h
> @@ -2367,7 +2367,7 @@ do {                                                                      \
>  /*
>   * Macros to access the floating point coprocessor control registers
>   */
> -#define _read_32bit_cp1_register(source, gas_hardfloat)                        \
> +#define read_32bit_cp1_register(source)                                        \
>  ({                                                                     \
>         unsigned int __res;                                             \
>                                                                         \
> @@ -2377,36 +2377,24 @@ do {                                                                    \
>         "       # gas fails to assemble cfc1 for some archs,    \n"     \
>         "       # like Octeon.                                  \n"     \
>         "       .set    mips1                                   \n"     \
> -       "       "STR(gas_hardfloat)"                            \n"     \
> +       "       .set hardfloat                                  \n"     \
>         "       cfc1    %0,"STR(source)"                        \n"     \
>         "       .set    pop                                     \n"     \
>         : "=r" (__res));                                                \
>         __res;                                                          \
>  })
>
> -#define _write_32bit_cp1_register(dest, val, gas_hardfloat)            \
> +#define write_32bit_cp1_register(dest, val)                            \
>  do {                                                                   \
>         __asm__ __volatile__(                                           \
>         "       .set    push                                    \n"     \
>         "       .set    reorder                                 \n"     \
> -       "       "STR(gas_hardfloat)"                            \n"     \
> +       "       .set hardfloat                                  \n"     \
>         "       ctc1    %0,"STR(dest)"                          \n"     \
>         "       .set    pop                                     \n"     \
>         : : "r" (val));                                                 \
>  } while (0)
>
> -#ifdef GAS_HAS_SET_HARDFLOAT
> -#define read_32bit_cp1_register(source)                                        \
> -       _read_32bit_cp1_register(source, .set hardfloat)
> -#define write_32bit_cp1_register(dest, val)                            \
> -       _write_32bit_cp1_register(dest, val, .set hardfloat)
> -#else
> -#define read_32bit_cp1_register(source)                                        \
> -       _read_32bit_cp1_register(source, )
> -#define write_32bit_cp1_register(dest, val)                            \
> -       _write_32bit_cp1_register(dest, val, )
> -#endif
> -
>  #ifdef TOOLCHAIN_SUPPORTS_DSP
>  #define rddsp(mask)                                                    \
>  ({                                                                     \
> diff --git a/arch/mips/kernel/genex.S b/arch/mips/kernel/genex.S
> index 3425df6019c0..b6de8e88c1bd 100644
> --- a/arch/mips/kernel/genex.S
> +++ b/arch/mips/kernel/genex.S
> @@ -480,7 +480,7 @@ NESTED(nmi_handler, PT_SIZE, sp)
>         .set    push
>         /* gas fails to assemble cfc1 for some archs (octeon).*/ \
>         .set    mips1
> -       SET_HARDFLOAT
> +       .set    hardfloat
>         cfc1    a1, fcr31
>         .set    pop
>         .endm
> diff --git a/arch/mips/kernel/r2300_fpu.S b/arch/mips/kernel/r2300_fpu.S
> index 2748c55820c2..6c745aa9e825 100644
> --- a/arch/mips/kernel/r2300_fpu.S
> +++ b/arch/mips/kernel/r2300_fpu.S
> @@ -64,7 +64,7 @@ LEAF(_restore_fp)
>   */
>  LEAF(_save_fp_context)
>         .set    push
> -       SET_HARDFLOAT
> +       .set    hardfloat
>         li      v0, 0                                   # assume success
>         cfc1    t1, fcr31
>         EX2(s.d $f0, 0(a0))
> @@ -98,7 +98,7 @@ LEAF(_save_fp_context)
>   */
>  LEAF(_restore_fp_context)
>         .set    push
> -       SET_HARDFLOAT
> +       .set    hardfloat
>         li      v0, 0                                   # assume success
>         EX(lw t0, (a1))
>         EX2(l.d $f0, 0(a0))
> diff --git a/arch/mips/kernel/r4k_fpu.S b/arch/mips/kernel/r4k_fpu.S
> index 2e687c60bc4f..4e8c98517d9d 100644
> --- a/arch/mips/kernel/r4k_fpu.S
> +++ b/arch/mips/kernel/r4k_fpu.S
> @@ -26,7 +26,7 @@
>
>         .macro  EX insn, reg, src
>         .set    push
> -       SET_HARDFLOAT
> +       .set    hardfloat
>         .set    nomacro
>  .ex\@: \insn   \reg, \src
>         .set    pop
> @@ -98,14 +98,14 @@ LEAF(_init_msa_upper)
>   */
>  LEAF(_save_fp_context)
>         .set    push
> -       SET_HARDFLOAT
> +       .set    hardfloat
>         cfc1    t1, fcr31
>         .set    pop
>
>  #if defined(CONFIG_64BIT) || defined(CONFIG_CPU_MIPSR2) || \
>      defined(CONFIG_CPU_MIPSR5) || defined(CONFIG_CPU_MIPSR6)
>         .set    push
> -       SET_HARDFLOAT
> +       .set    hardfloat
>  #if defined(CONFIG_CPU_MIPSR2) || defined(CONFIG_CPU_MIPSR5)
>         .set    mips32r2
>         .set    fp=64
> @@ -135,7 +135,7 @@ LEAF(_save_fp_context)
>  #endif
>
>         .set push
> -       SET_HARDFLOAT
> +       .set    hardfloat
>         /* Store the 16 even double precision registers */
>         EX      sdc1 $f0, 0(a0)
>         EX      sdc1 $f2, 16(a0)
> @@ -173,7 +173,7 @@ LEAF(_restore_fp_context)
>  #if defined(CONFIG_64BIT) || defined(CONFIG_CPU_MIPSR2) || \
>      defined(CONFIG_CPU_MIPSR5) || defined(CONFIG_CPU_MIPSR6)
>         .set    push
> -       SET_HARDFLOAT
> +       .set    hardfloat
>  #if defined(CONFIG_CPU_MIPSR2) || defined(CONFIG_CPU_MIPSR5)
>         .set    mips32r2
>         .set    fp=64
> @@ -201,7 +201,7 @@ LEAF(_restore_fp_context)
>  1:     .set pop
>  #endif
>         .set push
> -       SET_HARDFLOAT
> +       .set hardfloat
>         EX      ldc1 $f0, 0(a0)
>         EX      ldc1 $f2, 16(a0)
>         EX      ldc1 $f4, 32(a0)
> diff --git a/arch/mips/kvm/fpu.S b/arch/mips/kvm/fpu.S
> index 16f17c6390dd..eb2e8cc3532f 100644
> --- a/arch/mips/kvm/fpu.S
> +++ b/arch/mips/kvm/fpu.S
> @@ -22,7 +22,7 @@
>
>  LEAF(__kvm_save_fpu)
>         .set    push
> -       SET_HARDFLOAT
> +       .set    hardfloat
>         .set    fp=64
>         mfc0    t0, CP0_STATUS
>         sll     t0, t0, 5                       # is Status.FR set?
> @@ -66,7 +66,7 @@ LEAF(__kvm_save_fpu)
>
>  LEAF(__kvm_restore_fpu)
>         .set    push
> -       SET_HARDFLOAT
> +       .set    hardfloat
>         .set    fp=64
>         mfc0    t0, CP0_STATUS
>         sll     t0, t0, 5                       # is Status.FR set?
> @@ -110,7 +110,7 @@ LEAF(__kvm_restore_fpu)
>
>  LEAF(__kvm_restore_fcsr)
>         .set    push
> -       SET_HARDFLOAT
> +       .set    hardfloat
>         lw      t0, VCPU_FCR31(a0)
>         /*
>          * The ctc1 must stay at this offset in __kvm_restore_fcsr.
>
> --
> 2.39.0



-- 
Thanks,
~Nick Desaulniers



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