MaskRay

Interesting to see that people are still spending much time on assembly languages :) I've had a lot of fun with it in recent years as well. (Shameless plug: I've written a few on LLVM integrated assembler regarding better fragments and improving expressions and relocations).

When comparing GNU Assembler and MASM, GAS is missing many features: while loop, string processing (.e.g strlen)

> page 3: "It’s important to understand that MASM converts macro invocation arguments to text values before doing the macro expansion"

Like MASM, GAS uses call-by-name evaluation by default. While GAS's altmacro mode does allow for expression evaluation using syntax like `%(1+2)`, it has strict limitations: it only supports absolute expressions and is restricted to argument positions.

In contrast, MASM's % operator (page 8) looks far more general.

While we could utilize zigzag encoding (i>>31) ^ (i<<1) to convert SLEB128-encoded type/addend to use ULEB128 instead, the generate code is inferior to or on par with SLEB128 for one-byte encodings on x86, AArch64, and RISC-V. Haven't tried wider values - but zigzag encoding is likely slower as well

// One-byte case for SLEB128 int64_t from_signext(uint64_t v) { return v < 64 ? v - 128 : v; }

// One-byte case for ULEB128 with zig-zag encoding int64_t from_zigzag(uint64_t z) { return (z >> 1) ^ -(z & 1); }

git switch v6.9

The riscv build succeeded. For the x86-64 build I ran into

    % make O=/tmp/linux/x86 ARCH=x86_64 CC=/tmp/p/claudes-c-compiler/target/release/ccc-x86 HOSTCC=/tmp/p/claudes-c-compiler/target/release/ccc-x86 LDFLAGS=-fuse-ld=bfd LD=ld.bfd -j30 vmlinux -k
    make[1]: Entering directory '/tmp/linux/x86'
    ...
      CC      arch/x86/platform/intel/iosf_mbi.o
    ccc: error: lgdtl requires memory operand
      AR      arch/x86/platform/intel-mid/built-in.a
    make[6]: *** [/home/ray/Dev/linux/scripts/Makefile.build:362: arch/x86/realmode/rm/wakeup_asm.o] Error 1
    ld.bfd: arch/x86/entry/vdso/vdso32/sigreturn.o: warning: relocation in read-only section `.eh_frame'
    ld.bfd: error in arch/x86/entry/vdso/vdso32/sigreturn.o(.eh_frame); no .eh_frame_hdr table will be created
    ld.bfd: warning: creating DT_TEXTREL in a shared object
    ccc: error: unsupported pushw operand

There are many other errors.

tinyconfig and allnoconfig have fewer errors.

    RELOCS  arch/x86/realmode/rm/realmode.relocs
    Invalid absolute R_386_32 relocation: real_mode_seg

Still very impressive.

I want to verify the claim that it builds the Linux kernel. It quickly runs into errors, but yeah, still pretty cool!

make O=/tmp/linux/x86 ARCH=x86_64 CC=/tmp/p/claudes-c-compiler/target/release/ccc -j30 defconfig all

``` /home/ray/Dev/linux/arch/x86/include/asm/preempt.h:44:184: error: expected ';' after expression before 'pto_tmp__' do { u32 pto_val__ = ((u32)(((unsigned long) ~0x80000000) & 0xffffffff)); if (0) { __typeof_unqual__((__preempt_count)) pto_tmp__; pto_tmp__ = (~0x80000000); (void)pto_tmp__; } asm ("and" "l " "%[val], " "%" "[var]" : [var] "+m" (((__preempt_count))) : [val] "ri" (pto_val__)); } while (0); ^~~~~~~~~ fix-it hint: insert ';' /home/ray/Dev/linux/arch/x86/include/asm/preempt.h:49:183: error: expected ';' after expression before 'pto_tmp__' do { u32 pto_val__ = ((u32)(((unsigned long) 0x80000000) & 0xffffffff)); if (0) { __typeof_unqual__((__preempt_count)) pto_tmp__; pto_tmp__ = (0x80000000); (void)pto_tmp__; } asm ("or" "l " "%[val], " "%" "[var]" : [var] "+m" (((__preempt_count))) : [val] "ri" (pto_val__)); } while (0); ^~~~~~~~~ fix-it hint: insert ';' /home/ray/Dev/linux/arch/x86/include/asm/preempt.h:61:212: error: expected ';' after expression before 'pao_tmp__' ```

I recall that google3 switched to -funsigned-char for x86-64 a long time ago.