#8955: Syscall intrinsic -------------------------------------+------------------------------------- Reporter: schyler | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler | Version: 7.6.3 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: Type of failure: Runtime | Unknown/Multiple performance bug | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Changes (by slyfox): * cc: slyfox (added) Comment: What is your vision on how it's supposed to be used in haskell? A new 'foreign import' type per OS/arch target type? A new syntax to be able to call assembly instructions directly from haskell?
Also, marginally increased speed for calling syscalls since it doesn't need to go through libffi into C-land.
On at least i386 and amd64 GHC does not use libffi to call simple libc functions. For 'foreign import ccall unsafe' symbols GHC emits '''call <symbol>''' instruction directly. Native/via-libc difference might be in order of a few instructions. Note the amount of existing indirections: {{{#!hs module M where import Foreign.C foreign import ccall unsafe "foo" c_foo :: CInt -> IO CInt }}} gets translated to {{{ .section .data .align 8 .align 1 .globl __stginit_M .type __stginit_M, @object __stginit_M: .section .rodata .align 8 .align 1 c2oj_str: .byte 109 .byte 97 .byte 105 .byte 110 .byte 0 .section .data .align 8 .align 1 .globl M_zdtrModule2_closure .type M_zdtrModule2_closure, @object M_zdtrModule2_closure: .quad ghczmprim_GHCziTypes_TrNameS_static_info .quad c2oj_str .section .rodata .align 8 .align 1 c2om_str: .byte 77 .byte 0 .section .data .align 8 .align 1 .globl M_zdtrModule1_closure .type M_zdtrModule1_closure, @object M_zdtrModule1_closure: .quad ghczmprim_GHCziTypes_TrNameS_static_info .quad c2om_str .section .data .align 8 .align 1 .globl M_zdtrModule_closure .type M_zdtrModule_closure, @object M_zdtrModule_closure: .quad ghczmprim_GHCziTypes_Module_static_info .quad M_zdtrModule2_closure+1 .quad M_zdtrModule1_closure+1 .quad 3 .section .data .align 8 .align 1 r2eE_closure: .quad r2eE_info .section .text .align 8 .align 8 .quad 8589934597 .quad 0 .quad 15 r2eE_info: .Lc2ow: leaq -8(%rbp),%rax cmpq %r15,%rax jb .Lc2oF .Lc2oG: movq $c2ot_info,-8(%rbp) movq %r14,%rbx addq $-8,%rbp testb $7,%bl jne .Lc2ot .Lc2ou: jmp *(%rbx) .Lc2oJ: movq $16,904(%r13) jmp stg_gc_unpt_r1 .align 8 .quad 0 .quad 31 c2ot_info: .Lc2ot: addq $16,%r12 cmpq 856(%r13),%r12 ja .Lc2oJ .Lc2oI: movq 7(%rbx),%rdi subq $8,%rsp xorl %eax,%eax call foo addq $8,%rsp movq $base_GHCziInt_I32zh_con_info,-8(%r12) movslq %eax,%rax movq %rax,(%r12) leaq -7(%r12),%rbx addq $8,%rbp jmp *(%rbp) .Lc2oF: movl $r2eE_closure,%ebx jmp *-8(%r13) .size r2eE_info, .-r2eE_info .section .data .align 8 .align 1 .globl M_czufoo_closure .type M_czufoo_closure, @object M_czufoo_closure: .quad M_czufoo_info .section .text .align 8 .align 8 .quad 8589934597 .quad 0 .quad 15 .globl M_czufoo_info .type M_czufoo_info, @object M_czufoo_info: .Lc2oT: jmp r2eE_info .size M_czufoo_info, .-M_czufoo_info .section .data.rel.ro .align 8 .align 1 S2p0_srt: .section .note.GNU-stack,"",@progbits .ident "GHC 8.1.20160817" }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8955#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler