Rework deferred compilation mechanism.

Author: vchuravy

examples/jit.jl

@@ -116,31 +116,31 @@ function get_trampoline(job)
     return addr
 end
 
-import GPUCompiler: deferred_codegen_jobs
-@generated function deferred_codegen(f::F, ::Val{tt}, ::Val{world}) where {F,tt,world}
-    # manual version of native_job because we have a function type
-    source = methodinstance(F, Base.to_tuple_type(tt), world)
-    target = NativeCompilerTarget(; jlruntime=true, llvm_always_inline=true)
-    # XXX: do we actually require the Julia runtime?
-    #      with jlruntime=false, we reach an unreachable.
-    params = TestCompilerParams()
-    config = CompilerConfig(target, params; kernel=false)
-    job = CompilerJob(source, config, world)
-    # XXX: invoking GPUCompiler from a generated function is not allowed!
-    #      for things to work, we need to forward the correct world, at least.
-
-    addr = get_trampoline(job)
-    trampoline = pointer(addr)
-    id = Base.reinterpret(Int, trampoline)
-
-    deferred_codegen_jobs[id] = job
-
-    quote
-        ptr = ccall("extern deferred_codegen", llvmcall, Ptr{Cvoid}, (Ptr{Cvoid},), $trampoline)
-        assume(ptr != C_NULL)
-        return ptr
-    end
-end
+# import GPUCompiler: deferred_codegen_jobs
+# @generated function deferred_codegen(f::F, ::Val{tt}, ::Val{world}) where {F,tt,world}
+#     # manual version of native_job because we have a function type
+#     source = methodinstance(F, Base.to_tuple_type(tt), world)
+#     target = NativeCompilerTarget(; jlruntime=true, llvm_always_inline=true)
+#     # XXX: do we actually require the Julia runtime?
+#     #      with jlruntime=false, we reach an unreachable.
+#     params = TestCompilerParams()
+#     config = CompilerConfig(target, params; kernel=false)
+#     job = CompilerJob(source, config, world)
+#     # XXX: invoking GPUCompiler from a generated function is not allowed!
+#     #      for things to work, we need to forward the correct world, at least.
+
+#     addr = get_trampoline(job)
+#     trampoline = pointer(addr)
+#     id = Base.reinterpret(Int, trampoline)
+
+#     deferred_codegen_jobs[id] = job
+
+#     quote
+#         ptr = ccall("extern deferred_codegen", llvmcall, Ptr{Cvoid}, (Ptr{Cvoid},), $trampoline)
+#         assume(ptr != C_NULL)
+#         return ptr
+#     end
+# end
 
 @generated function abi_call(f::Ptr{Cvoid}, rt::Type{RT}, tt::Type{T}, func::F, args::Vararg{Any, N}) where {T, RT, F, N}
     argtt    = tt.parameters[1]
@@ -224,8 +224,9 @@ end
 @inline function call_delayed(f::F, args...) where F
     tt = Tuple{map(Core.Typeof, args)...}
     rt = Core.Compiler.return_type(f, tt)
-    world = GPUCompiler.tls_world_age()
-    ptr = deferred_codegen(f, Val(tt), Val(world))
+    # FIXME: Horrible idea, have `var"gpuc.deferred"` actually do the work
+    #        But that will only be needed here, and in Enzyme...
+    ptr = GPUCompiler.var"gpuc.deferred"(f, args...)
     abi_call(ptr, rt, tt, f, args...)
 end
 

src/driver.jl

@@ -39,6 +39,17 @@ function JuliaContext(f; kwargs...)
 end
 
 
+## deferred compilation
+
+"""
+    var"gpuc.deferred"(f, args...)::Ptr{Cvoid}
+
+As if we were to call `f(args...)` but instead we are
+putting down a marker and return a function pointer to later
+call.
+"""
+function var"gpuc.deferred" end
+
 ## compiler entrypoint
 
 export compile
@@ -127,33 +138,6 @@ function codegen(output::Symbol, @nospecialize(job::CompilerJob); toplevel::Bool
     error("Unknown compilation output $output")
 end
 
-# primitive mechanism for deferred compilation, for implementing CUDA dynamic parallelism.
-# this could both be generalized (e.g. supporting actual function calls, instead of
-# returning a function pointer), and be integrated with the nonrecursive codegen.
-const deferred_codegen_jobs = Dict{Int, Any}()
-
-# We make this function explicitly callable so that we can drive OrcJIT's
-# lazy compilation from, while also enabling recursive compilation.
-Base.@ccallable Ptr{Cvoid} function deferred_codegen(ptr::Ptr{Cvoid})
-    ptr
-end
-
-@generated function deferred_codegen(::Val{ft}, ::Val{tt}) where {ft,tt}
-    id = length(deferred_codegen_jobs) + 1
-    deferred_codegen_jobs[id] = (; ft, tt)
-    # don't bother looking up the method instance, as we'll do so again during codegen
-    # using the world age of the parent.
-    #
-    # this also works around an issue on <1.10, where we don't know the world age of
-    # generated functions so use the current world counter, which may be too new
-    # for the world we're compiling for.
-
-    quote
-        # TODO: add an edge to this method instance to support method redefinitions
-        ccall("extern deferred_codegen", llvmcall, Ptr{Cvoid}, (Int,), $id)
-    end
-end
-
 const __llvm_initialized = Ref(false)
 
 @locked function emit_llvm(@nospecialize(job::CompilerJob); toplevel::Bool,
@@ -183,79 +167,76 @@ const __llvm_initialized = Ref(false)
     entry = finish_module!(job, ir, entry)
 
     # deferred code generation
-    has_deferred_jobs = toplevel && !only_entry && haskey(functions(ir), "deferred_codegen")
-    jobs = Dict{CompilerJob, String}(job => entry_fn)
-    if has_deferred_jobs
-        dyn_marker = functions(ir)["deferred_codegen"]
-
-        # iterative compilation (non-recursive)
-        changed = true
-        while changed
-            changed = false
-
-            # find deferred compiler
-            # TODO: recover this information earlier, from the Julia IR
-            worklist = Dict{CompilerJob, Vector{LLVM.CallInst}}()
-            for use in uses(dyn_marker)
-                # decode the call
-                call = user(use)::LLVM.CallInst
-                id = convert(Int, first(operands(call)))
-
-                global deferred_codegen_jobs
-                dyn_val = deferred_codegen_jobs[id]
-
-                # get a job in the appopriate world
-                dyn_job = if dyn_val isa CompilerJob
-                    # trust that the user knows what they're doing
-                    dyn_val
+    run_optimization_for_deferred = false
+    if haskey(functions(ir), "gpuc.lookup")
+        run_optimization_for_deferred = true
+        dyn_marker = functions(ir)["gpuc.lookup"]
+
+        # gpuc.deferred is lowered to a gpuc.lookup foreigncall, so we need to extract the
+        # target method instance from the LLVM IR
+        function find_base_object(val)
+            while true
+                if val isa ConstantExpr && (opcode(val) == LLVM.API.LLVMIntToPtr ||
+                                            opcode(val) == LLVM.API.LLVMBitCast ||
+                                            opcode(val) == LLVM.API.LLVMAddrSpaceCast)
+                    val = first(operands(val))
+                elseif val isa LLVM.IntToPtrInst ||
+                       val isa LLVM.BitCastInst ||
+                       val isa LLVM.AddrSpaceCastInst
+                    val = first(operands(val))
+                elseif val isa LLVM.LoadInst
+                    # In 1.11+ we no longer embed integer constants directly.
+                    gv = first(operands(val))
+                    if gv isa LLVM.GlobalValue
+                        val = LLVM.initializer(gv)
+                        continue
+                    end
+                    break
                 else
-                    ft, tt = dyn_val
-                    dyn_src = methodinstance(ft, tt, tls_world_age())
-                    CompilerJob(dyn_src, job.config)
+                    break
                 end
-
-                push!(get!(worklist, dyn_job, LLVM.CallInst[]), call)
             end
+            return val
+        end
 
-            # compile and link
-            for dyn_job in keys(worklist)
-                # cached compilation
-                dyn_entry_fn = get!(jobs, dyn_job) do
-                    dyn_ir, dyn_meta = codegen(:llvm, dyn_job; toplevel=false,
-                                                               parent_job=job)
-                    dyn_entry_fn = LLVM.name(dyn_meta.entry)
-                    merge!(compiled, dyn_meta.compiled)
-                    @assert context(dyn_ir) == context(ir)
-                    link!(ir, dyn_ir)
-                    changed = true
-                    dyn_entry_fn
-                end
-                dyn_entry = functions(ir)[dyn_entry_fn]
-
-                # insert a pointer to the function everywhere the entry is used
-                T_ptr = convert(LLVMType, Ptr{Cvoid})
-                for call in worklist[dyn_job]
-                    @dispose builder=IRBuilder() begin
-                        position!(builder, call)
-                        fptr = if LLVM.version() >= v"17"
-                            T_ptr = LLVM.PointerType()
-                            bitcast!(builder, dyn_entry, T_ptr)
-                        elseif VERSION >= v"1.12.0-DEV.225"
-                            T_ptr = LLVM.PointerType(LLVM.Int8Type())
-                            bitcast!(builder, dyn_entry, T_ptr)
-                        else
-                            ptrtoint!(builder, dyn_entry, T_ptr)
-                        end
-                        replace_uses!(call, fptr)
+        worklist = Dict{Any, Vector{LLVM.CallInst}}()
+        for use in uses(dyn_marker)
+            # decode the call
+            call = user(use)::LLVM.CallInst
+            dyn_mi_inst = find_base_object(operands(call)[1])
+            @compiler_assert isa(dyn_mi_inst, LLVM.ConstantInt) job
+            dyn_mi = Base.unsafe_pointer_to_objref(
+                convert(Ptr{Cvoid}, convert(Int, dyn_mi_inst)))
+            push!(get!(worklist, dyn_mi, LLVM.CallInst[]), call)
+        end
+
+        for dyn_mi in keys(worklist)
+            dyn_fn_name = compiled[dyn_mi].specfunc
+            dyn_fn = functions(ir)[dyn_fn_name]
+
+            # insert a pointer to the function everywhere the entry is used
+            T_ptr = convert(LLVMType, Ptr{Cvoid})
+            for call in worklist[dyn_mi]
+                @dispose builder=IRBuilder() begin
+                    position!(builder, call)
+                    fptr = if LLVM.version() >= v"17"
+                        T_ptr = LLVM.PointerType()
+                        bitcast!(builder, dyn_fn, T_ptr)
+                    elseif VERSION >= v"1.12.0-DEV.225"
+                        T_ptr = LLVM.PointerType(LLVM.Int8Type())
+                        bitcast!(builder, dyn_fn, T_ptr)
+                    else
+                        ptrtoint!(builder, dyn_fn, T_ptr)
                     end
-                    erase!(call)
+                    replace_uses!(call, fptr)
                 end
+                unsafe_delete!(LLVM.parent(call), call)
             end
         end
 
         # all deferred compilations should have been resolved
         @compiler_assert isempty(uses(dyn_marker)) job
-        erase!(dyn_marker)
+        unsafe_delete!(ir, dyn_marker)
     end
 
     if libraries
@@ -285,7 +266,7 @@ const __llvm_initialized = Ref(false)
         # global variables. this makes sure that the optimizer can, e.g.,
         # rewrite function signatures.
         if toplevel
-            preserved_gvs = collect(values(jobs))
+            preserved_gvs = [entry_fn]
             for gvar in globals(ir)
                 if linkage(gvar) == LLVM.API.LLVMExternalLinkage
                     push!(preserved_gvs, LLVM.name(gvar))
@@ -317,7 +298,7 @@ const __llvm_initialized = Ref(false)
                 # deferred codegen has some special optimization requirements,
                 # which also need to happen _after_ regular optimization.
                 # XXX: make these part of the optimizer pipeline?
-                if has_deferred_jobs
+                if run_optimization_for_deferred
                     @dispose pb=NewPMPassBuilder() begin
                         add!(pb, NewPMFunctionPassManager()) do fpm
                             add!(fpm, InstCombinePass())
@@ -353,15 +334,15 @@ const __llvm_initialized = Ref(false)
         # finish the module
         #
         # we want to finish the module after optimization, so we cannot do so
-        # during deferred code generation. instead, process the deferred jobs
-        # here.
+        # during deferred code generation. Instead, process the merged module
+        # from all the jobs here.
         if toplevel
             entry = finish_ir!(job, ir, entry)
 
-            for (job′, fn′) in jobs
-                job′ == job && continue
-                finish_ir!(job′, ir, functions(ir)[fn′])
-            end
+            # for (job′, fn′) in jobs
+            #     job′ == job && continue
+            #     finish_ir!(job′, ir, functions(ir)[fn′])
+            # end
         end
 
         # replace non-entry function definitions with a declaration

src/irgen.jl

@@ -80,6 +80,17 @@ function irgen(@nospecialize(job::CompilerJob))
     compiled[job.source] =
         (; compiled[job.source].ci, func, specfunc)
 
+    # Earlier we sanitize global names, this invalidates the
+    # func, specfunc names safed in compiled. Update the names now,
+    # such that when when use the compiled mappings to lookup the
+    # llvm function for a methodinstance (deferred codegen) we have 
+    # valid targets.
+    for mi in keys(compiled)
+        mi == job.source && continue
+        ci, func, specfunc = compiled[mi]
+        compiled[mi] = (; ci, func=safe_name(func), specfunc=safe_name(specfunc))
+    end
+
     # minimal required optimization
     @timeit_debug to "rewrite" begin
         if job.config.kernel && needs_byval(job)