Codegen regression in check_top_bit after MethodInstance/CodeInstance split

[maleadt]

Ran into this because invoke is GPU incompatible and check_top_bit is used by integer conversions. Nonetheless, it seems bad to have a dynamic dispatch and gcframe in such hot code. It kinda defeats the purpose of the noinline throw_inexacterror.

Bisected to #31191:

commit 8c445663547791e59f33f9e8d49b276332107614
Author: Jameson Nash <vtjnash@gmail.com>
Date:   Fri Mar 29 12:11:33 2019 -0400

    internals: better representation for code (#31191)

   _       _ _(_)_     |  Documentation: https://docs.julialang.org
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   _ _   _| |_  __ _   |  Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 1.2.0-DEV.573 (2019-03-29)
 _/ |\__'_|_|_|\__'_|  |  Commit 8c44566354* (26 days old master)
|__/                   |

julia> code_llvm(Core.check_top_bit, Tuple{UInt})

;  @ boot.jl:573 within `check_top_bit'
define i64 @julia_check_top_bit_10434(i64) {
top:
  %1 = alloca %jl_value_t addrspace(10)*, i32 4
  %gcframe = alloca %jl_value_t addrspace(10)*, i32 3
  %2 = bitcast %jl_value_t addrspace(10)** %gcframe to i8*
  call void @llvm.memset.p0i8.i32(i8* %2, i8 0, i32 24, i32 0, i1 false)
  %thread_ptr = call i8* asm "movq %fs:0, $0", "=r"()
  %ptls_i8 = getelementptr i8, i8* %thread_ptr, i64 -15560
  %ptls = bitcast i8* %ptls_i8 to %jl_value_t***
;  @ boot.jl:574 within `check_top_bit'
; ┌ @ boot.jl:564 within `is_top_bit_set'
   %3 = getelementptr %jl_value_t addrspace(10)*, %jl_value_t addrspace(10)** %gcframe, i32 0
   %4 = bitcast %jl_value_t addrspace(10)** %3 to i64*
   store i64 2, i64* %4
   %5 = getelementptr %jl_value_t**, %jl_value_t*** %ptls, i32 0
   %6 = load %jl_value_t**, %jl_value_t*** %5
   %7 = getelementptr %jl_value_t addrspace(10)*, %jl_value_t addrspace(10)** %gcframe, i32 1
   %8 = bitcast %jl_value_t addrspace(10)** %7 to %jl_value_t***
   store %jl_value_t** %6, %jl_value_t*** %8
   %9 = bitcast %jl_value_t*** %5 to %jl_value_t addrspace(10)***
   store %jl_value_t addrspace(10)** %gcframe, %jl_value_t addrspace(10)*** %9
   %10 = icmp sgt i64 %0, -1
; └
  br i1 %10, label %L7, label %L5

L5:                                               ; preds = %top
  %11 = call %jl_value_t addrspace(10)* @jl_box_uint64(i64 zeroext %0)
  %12 = getelementptr %jl_value_t addrspace(10)*, %jl_value_t addrspace(10)** %gcframe, i32 2
  store %jl_value_t addrspace(10)* %11, %jl_value_t addrspace(10)** %12
  %13 = getelementptr %jl_value_t addrspace(10)*, %jl_value_t addrspace(10)** %1, i32 0
  store %jl_value_t addrspace(10)* addrspacecast (%jl_value_t* inttoptr (i64 140226490904560 to %jl_value_t*) to %jl_value_t addrspace(10)*), %jl_value_t addrspace(10)** %13
  %14 = getelementptr %jl_value_t addrspace(10)*, %jl_value_t addrspace(10)** %1, i32 1
  store %jl_value_t addrspace(10)* addrspacecast (%jl_value_t* inttoptr (i64 140226415235320 to %jl_value_t*) to %jl_value_t addrspace(10)*), %jl_value_t addrspace(10)** %14
  %15 = getelementptr %jl_value_t addrspace(10)*, %jl_value_t addrspace(10)** %1, i32 2
  store %jl_value_t addrspace(10)* addrspacecast (%jl_value_t* inttoptr (i64 140226418510032 to %jl_value_t*) to %jl_value_t addrspace(10)*), %jl_value_t addrspace(10)** %15
  %16 = getelementptr %jl_value_t addrspace(10)*, %jl_value_t addrspace(10)** %1, i32 3
  store %jl_value_t addrspace(10)* %11, %jl_value_t addrspace(10)** %16
  %17 = call nonnull %jl_value_t addrspace(10)* @jl_invoke(%jl_value_t addrspace(10)* addrspacecast (%jl_value_t* inttoptr (i64 140226491409328 to %jl_value_t*) to %jl_value_t addrspace(10)*), %jl_value_t addrspace(10)** %1, i32 4)
  call void @llvm.trap()
  unreachable

L7:                                               ; preds = %top
;  @ boot.jl:575 within `check_top_bit'
  %18 = getelementptr %jl_value_t addrspace(10)*, %jl_value_t addrspace(10)** %gcframe, i32 1
  %19 = load %jl_value_t addrspace(10)*, %jl_value_t addrspace(10)** %18
  %20 = getelementptr %jl_value_t**, %jl_value_t*** %ptls, i32 0
  %21 = bitcast %jl_value_t*** %20 to %jl_value_t addrspace(10)**
  store %jl_value_t addrspace(10)* %19, %jl_value_t addrspace(10)** %21
  ret i64 %0
}

Latest good commit, right before that:

commit 4b1230277ca50c70ee517578db1ec30483cf9ad9
Author: Kristoffer Carlsson <kristoffer.carlsson@chalmers.se>
Date:   Fri Mar 29 16:16:47 2019 +0100

    add a nop conversion for some (#31536)

    _       _ _(_)_     |  Documentation: https://docs.julialang.org
  (_)     | (_) (_)    |
   _ _   _| |_  __ _   |  Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 1.2.0-DEV.572 (2019-03-29)
 _/ |\__'_|_|_|\__'_|  |  Commit 4b1230277c* (26 days old master)
|__/                   |

julia> code_llvm(Core.check_top_bit, Tuple{UInt})

;  @ boot.jl:570 within `check_top_bit'
define i64 @julia_check_top_bit_8001(i64) {
top:
;  @ boot.jl:571 within `check_top_bit'
; ┌ @ boot.jl:561 within `is_top_bit_set'
   %1 = icmp sgt i64 %0, -1
; └
  br i1 %1, label %L7, label %L5

L5:                                               ; preds = %top
  call void @julia_throw_inexacterror_90(%jl_value_t addrspace(10)* addrspacecast (%jl_value_t* inttoptr (i64 139625077153768 to %jl_value_t*) to %jl_value_t addrspace(10)*), %jl_value_t addrspace(10)* addrspacecast (%jl_value_t* inttoptr (i64 139625080981712 to %jl_value_t*) to %jl_value_t addrspace(10)*), i64 %0)
  call void @llvm.trap()
  unreachable

L7:                                               ; preds = %top
;  @ boot.jl:572 within `check_top_bit'
  ret i64 %0
}

Adding to the 1.2 milestone (are we doing that now we've branched?) since it seems bad to have this in a release, and it breaks lots of GPU code.

[KristofferC]

Adding to the 1.2 milestone (are we doing that now we've branched?)

Yes.