Object representation (in slack-jp)

Coerce2.hs

import Unsafe.Coerce


{-# NOINLINE bool_var1 #-}
bool_var1 :: Bool
bool_var1 = True


main :: IO ()
main = print $ (unsafeCoerce bool_var1 :: Int)

Execution.txt

------------------------------------------------------------------------
$ ./Coerce2 
4611686018427405893
(0x4000_0000_0000_4645)



------------------------------------------------------------------------
$ ghc -O -fforce-recomp -ddump-stg     Coerce2.hs > z.stg

Main.bool_var1 [InlPrag=NOINLINE] :: GHC.Types.Bool
[GblId, Caf=NoCafRefs, Unf=OtherCon []] =
    CCS_DONT_CARE GHC.Types.True! [];


------------------------------------------------------------------------
$ ghc -O -fforce-recomp -ddump-opt-cmm Coerce2.hs > z.opt-cmm

section ""data" . Main.bool_var1_closure" {
    Main.bool_var1_closure:
        const GHC.Types.True_con_info;
}


------------------------------------------------------------------------
$ ghc -O -fforce-recomp -ddump-asm     Coerce2.hs > z.asm

.section .data
.align 8
.align 1
.globl Main.bool_var1_closure
.type Main.bool_var1_closure, @object
Main.bool_var1_closure:
        .quad   GHC.Types.True_con_info


------------------------------------------------------------------------
$ objdump -D Coerce2 > z.disas

00000000004a4300 <Main_boolzuvar1_closure>:                           <----- closure(info ptr) of "Main.bool_var1" 
  4a4300:       38 44 46 00             cmp    %al,0x0(%rsi,%rax,2)
  4a4304:       00 00                   add    %al,(%rax)
        ...

00000000004a4308 <Main_zdtrModule3_closure>:
  4a4308:       98                      cwtl   
  4a4309:       45                      rex.RB                        <----- +9 (little endian)
  4a430a:       46 00 00                rex.RX add %r8b,(%rax)
  4a430d:       00 00                   add    %al,(%rax)
  4a430f:       00 40 ba                add    %al,-0x46(%rax)
  4a4312:       48 00 00                rex.W add %al,(%rax)
  4a4315:       00 00                   add    %al,(%rax)


0000000000464438 <ghczmprim_GHCziTypes_True_con_info>:
  464438:       48 83 c3 02             add    $0x2,%rbx
  46443c:       ff 65 00                jmpq   *0x0(%rbp)
  46443f:       90                      nop