#16298: Awful(?) code in AArch64 stg_BLACKHOLE entry code -------------------------------------+------------------------------------- Reporter: bgamari | Owner: (none) Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.7 Resolution: | Keywords: Operating System: Unknown/Multiple | Architecture: aarch64 Type of failure: Runtime | Test Case: performance bug | Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by bgamari): I have been staring more at this code and have found it's even worse than I thought. Far more repetition than I would have thought would be necessary. Here's the full dump: {{{ Dump of assembler code for function stg_BLACKHOLE_info$def: 0x0000ffffb66d6118 <+0>: mov x23, x22 // x23 == x22 == blackhole closure 0x0000ffffb66d611c <+4>: ldr x22, [x22, #8] // x22 = bh->indirectee 0x0000ffffb66d6120 <+8>: tst x22, #0x7 // GET_TAG(bh->indirectee) == 0? 0x0000ffffb66d6124 <+12>: b.ne 0xffffb66d6224 // b.any 0x0000ffffb66d6128 <+16>: adrp x25, 0xffffb66fb000 0x0000ffffb66d612c <+20>: adrp x26, 0xffffb66fb000 0x0000ffffb66d6130 <+24>: adrp x27, 0xffffb66fb000 0x0000ffffb66d6134 <+28>: adrp x29, 0xffffb66fb000 0x0000ffffb66d6138 <+32>: ldr x25, [x25, #3880] 0x0000ffffb66d613c <+36>: ldr x26, [x26, #3888] 0x0000ffffb66d6140 <+40>: ldr x27, [x27, #3896] 0x0000ffffb66d6144 <+44>: ldr x29, [x29, #3904] 0x0000ffffb66d6148 <+48>: sub x24, x19, #0x18 0x0000ffffb66d614c <+52>: ldr x8, [x22] 0x0000ffffb66d6150 <+56>: cmp x8, x25 0x0000ffffb66d6154 <+60>: b.eq 0xffffb66d61a8 // b.none 0x0000ffffb66d6158 <+64>: cmp x8, x26 0x0000ffffb66d615c <+68>: b.eq 0xffffb66d6178 // b.none 0x0000ffffb66d6160 <+72>: cmp x8, x29 0x0000ffffb66d6164 <+76>: b.eq 0xffffb66d6178 // b.none 0x0000ffffb66d6168 <+80>: adrp x9, 0xffffb66fb000 0x0000ffffb66d616c <+84>: ldr x9, [x9, #3912] 0x0000ffffb66d6170 <+88>: cmp x8, x9 0x0000ffffb66d6174 <+92>: b.ne 0xffffb66d61b4 // b.any 0x0000ffffb66d6178 <+96>: orr w1, wzr, #0x4 0x0000ffffb66d617c <+100>: mov x0, x24 0x0000ffffb66d6180 <+104>: bl 0xffffb66c6fe8 <allocate> 0x0000ffffb66d6184 <+108>: str x27, [x0] 0x0000ffffb66d6188 <+112>: ldr x8, [x19, #872] 0x0000ffffb66d618c <+116>: mov x22, x0 0x0000ffffb66d6190 <+120>: mov x1, x22 0x0000ffffb66d6194 <+124>: stp x8, x23, [x0, #16] 0x0000ffffb66d6198 <+128>: mov x0, x24 0x0000ffffb66d619c <+132>: bl 0xffffb66ae648 <messageBlackHole> 0x0000ffffb66d61a0 <+136>: cbnz x0, 0xffffb66d61e4 0x0000ffffb66d61a4 <+140>: ldr x22, [x23, #8] 0x0000ffffb66d61a8 <+144>: tst x22, #0x7 0x0000ffffb66d61ac <+148>: b.eq 0xffffb66d614c // b.none 0x0000ffffb66d61b0 <+152>: b 0xffffb66d6224 0x0000ffffb66d61b4 <+156>: tst x22, #0x7 0x0000ffffb66d61b8 <+160>: b.ne 0xffffb66d6224 // b.any 0x0000ffffb66d61bc <+164>: b 0xffffb66d61c4 0x0000ffffb66d61c0 <+168>: ldr x8, [x22] // $x8 = indirectee->info => 0x0000ffffb66d61c4 <+172>: ldursw x9, [x8, #-8] 0x0000ffffb66d61c8 <+176>: sub x10, x9, #0x1b 0x0000ffffb66d61cc <+180>: cmp x10, #0x2 0x0000ffffb66d61d0 <+184>: b.cs 0xffffb66d6204 // b.hs, b.nlast 0x0000ffffb66d61d4 <+188>: ldr x22, [x22, #8] 0x0000ffffb66d61d8 <+192>: tst x22, #0x7 0x0000ffffb66d61dc <+196>: b.eq 0xffffb66d61c0 // b.none 0x0000ffffb66d61e0 <+200>: b 0xffffb66d6224 0x0000ffffb66d61e4 <+204>: ldr x8, [x19, #872] 0x0000ffffb66d61e8 <+208>: orr w9, wzr, #0x2 0x0000ffffb66d61ec <+212>: strh w9, [x8, #34] 0x0000ffffb66d61f0 <+216>: ldr x8, [x19, #872] 0x0000ffffb66d61f4 <+220>: str x22, [x8, #40] 0x0000ffffb66d61f8 <+224>: mov x22, x23 0x0000ffffb66d61fc <+228>: bl 0xffffb66d2808 0x0000ffffb66d6200 <+232>: ret 0x0000ffffb66d6204 <+236>: cmp x9, #0x19 0x0000ffffb66d6208 <+240>: b.hi 0xffffb66d6230 // b.pmore 0x0000ffffb66d620c <+244>: orr w10, wzr, #0x1 0x0000ffffb66d6210 <+248>: lsl x9, x10, x9 0x0000ffffb66d6214 <+252>: mov w10, #0x7f00 // #32512 0x0000ffffb66d6218 <+256>: movk w10, #0x280, lsl #16 0x0000ffffb66d621c <+260>: tst x9, x10 0x0000ffffb66d6220 <+264>: b.eq 0xffffb66d6230 // b.none 0x0000ffffb66d6224 <+268>: ldr x8, [x20] 0x0000ffffb66d6228 <+272>: blr x8 0x0000ffffb66d622c <+276>: ret 0x0000ffffb66d6230 <+280>: blr x8 0x0000ffffb66d6234 <+284>: ret End of assembler dump. }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/16298#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler