Re: [PATCH v2 2/2] LoongArch: When the code model is extreme, the symbol address is obtained through macro instructions regardless of the value of -mexplicit-relocs.

[Xi Ruoyao <xry111@xry111.site>]

On Wed, 2024-01-17 at 17:38 +0800, chenglulu wrote:
> 
> 在 2024/1/13 下午9:05, Xi Ruoyao 写道:
> > 在 2024-01-13星期六的 15:01 +0800，chenglulu写道：
> > > 在 2024/1/12 下午7:42, Xi Ruoyao 写道:
> > > > 在 2024-01-12星期五的 09:46 +0800，chenglulu写道：
> > > > 
> > > > > > I found an issue bootstrapping GCC with -mcmodel=extreme in BOOT_CFLAGS:
> > > > > > we need a target hook to tell the generic code
> > > > > > UNSPEC_LA_PCREL_64_PART{1,2} are just a wrapper around symbols, or we'll
> > > > > > see millions lines of messages like
> > > > > > 
> > > > > > ../../gcc/gcc/tree.h:4171:1: note: non-delegitimized UNSPEC
> > > > > > UNSPEC_LA_PCREL_64_PART1 (42) found in variable location
> > > > > I build GCC with -mcmodel=extreme in BOOT_CFLAGS, but I haven't reproduced the problem you mentioned.
> > > > > 
> > > > >       $ ../configure --host=loongarch64-linux-gnu --target=loongarch64-linux-gnu --build=loongarch64-linux-gnu \
> > > > >           --with-arch=loongarch64 --with-abi=lp64d --enable-tls --enable-languages=c,c++,fortran,lto --enable-plugin \
> > > > >           --disable-multilib --disable-host-shared --enable-bootstrap --enable-checking=release
> > > > >       $ make BOOT_FLAGS="-mcmodel=extreme"
> > > > > 
> > > > > What did I do wrong?:-(
> > > > BOOT_CFLAGS, not BOOT_FLAGS :).
> > > > 
> > > This is so strange. My compilation here stopped due to syntax problems,
> > > 
> > > and I still haven't reproduced the information you mentioned about
> > > UNSPEC_LA_PCREL_64_PART1.
> > I used:
> > 
> > ../gcc/configure --with-system-zlib --disable-fixincludes \
> >                   --enable-default-ssp --enable-default-pie \
> >                   --disable-werror --disable-multilib \
> >                   --prefix=/home/xry111/gcc-dev
> > 
> > and then
> > 
> > make STAGE1_{C,CXX}FLAGS="-O2 -g" -j8 \
> >       BOOT_{C,CXX}FLAGS="-O2 -g -mcmodel=extreme" &| tee gcc-build.log
> > 
> > I guess "-g" is needed to reproduce the issue as well as the messages
> > were produced in dwarf generation.
> > 
> I have reproduced this problem, and it can be solved by adding a hook.
> 
> But unfortunately, when using '-mcmodel=extreme -mexplicit-relocs=always'
> 
> to test spec2006 403.gcc, an error will occur. Others have not been 
> tested yet.
> 
> I roughly debugged it, and the problem should be this:
> 
> The problem is that the address of the instruction ‘ldx.d $r12, $r25, 
> $r6’ is wrong.
> 
> Wrong assembly:
> 
>     5826         pcalau12i       $r13,%got_pc_hi20(recog_data)
>   5827         addi.d  $r12,$r0,%got_pc_lo12(recog_data)
>   5828         lu32i.d $r12,%got64_pc_lo20(recog_data)
>   5829         lu52i.d $r12,$r12,%got64_pc_hi12(recog_data)
>   5830         ldx.d   $r12,$r13,$r12
>   5831         ld.b    $r8,$r12,997
>   5832         .loc 1 829 18 discriminator 1 view .LVU1527
>   5833         ble     $r8,$r0,.L476
>   5834         ld.d    $r6,$r3,16
>   5835         ld.d    $r9,$r3,88
>   5836 .LBB189 = .
>   5837         .loc 1 839 24 view .LVU1528
>   5838         alsl.d  $r7,$r19,$r19,2
>   5839         ldx.d   $r12,$r25,$r6
>   5840         addi.d  $r17,$r3,120
>   5841 .LBE189 = .
>   5842         .loc 1 829 18 discriminator 1 view .LVU1529
>   5843         or      $r13,$r0,$r0
>   5844         addi.d  $r4,$r12,992
> 
> Assembly that works fine using macros:
> 
> 3040         la.global       $r12,$r13,recog_data
> 3041         ld.b    $r9,$r12,997
> 3042         ble     $r9,$r0,.L475
> 3043         alsl.d  $r5,$r16,$r16,2
> 3044         la.global       $r15,$r17,recog_data
> 3045         addi.d  $r4,$r12,992
> 3046         addi.d  $r18,$r3,48
> 3047         or      $r13,$r0,$r0
> 
> Comparing the assembly, we can see that lines 5844 and 3045 have the 
> same function,
> 
> but there is a problem with the base address register optimization at 
> line 5844.
> 
> regrename.c.283r.loop2_init:
> 
> (insn 6 497 2741 34 (set (reg:DI 180 [ ivtmp.713D.15724 ])
>          (const_int 0 [0])) "regrename.c":829:18 discrim 1 156 
> {*movdi_64bit}
> (nil))
> (insn 2741 6 2744 34 (parallel [
>              (set (reg:DI 1502)
>                  (unspec:DI [
>                          (symbol_ref:DI ("recog_data") [flags 0xc0]  
> <var_decl 0x7f8c5ffd66c0 recog_data>)
>                      ] UNSPEC_LA_PCREL_64_PART1))
>              (set (reg/f:DI 1479)
>                  (unspec:DI [
>                          (symbol_ref:DI ("recog_data") [flags 0xc0]  
> <var_decl 0x7f8c5ffd66c0 recog_data>)
>                      ] UNSPEC_LA_PCREL_64_PART2))
>          ]) -1
>       (expr_list:REG_UNUSED (reg/f:DI 1479)
> (nil)))
> (insn 2744 2741 2745 34 (set (reg/f:DI 1503)
>          (mem:DI (plus:DI (reg/f:DI 1479)
>                  (reg:DI 1502)) [0  S8 A8])) 156 {*movdi_64bit}
>       (expr_list:REG_EQUAL (symbol_ref:DI ("recog_data") [flags 0xc0] 
> <var_decl 0x7f8c5ffd66c0 recog_data>)
> (nil)))
> 
> 
> Virtual register 1479 will be used in insn 2744, but register 1479 was
> assigned the REG_UNUSED attribute in the previous instruction.
> 
> The attached file is the wrong file.
> The compilation command is as follows:
> 
> $ ./gcc/cc1 -fpreprocessed regrename.i -quiet -dp -dumpbase regrename.c 
> -dumpbase-ext .c -mno-relax -mabi=lp64d -march=loongarch64 -mfpu=64 
> -msimd=lasx -mcmodel=extreme -mtune=loongarch64 -g3 -O2 
> -Wno-int-conversion -Wno-implicit-int -Wno-implicit-function-declaration 
> -Wno-incompatible-pointer-types -version -o regrename.s 
> -mexplicit-relocs=always -fdump-rtl-all-all

I've seen some "guality" test failures in GCC test suite as well. 
Normally I just ignore the guality failures but this time they look very
suspicious.  I'll investigate these issues...

-- 
Xi Ruoyao <xry111@xry111.site>
School of Aerospace Science and Technology, Xidian University