Add Julia pointer intrinsics.

Author: maleadt

src/interop.jl

@@ -9,5 +9,8 @@ const jlctx = Ref{LLVM.Context}()
 include("interop/base.jl")
 include("interop/asmcall.jl")
 include("interop/passes.jl")
+if VERSION >= v"1.5-"
+include("interop/pointer.jl")
+end
 
 end

src/interop/pointer.jl

@@ -0,0 +1,96 @@
+# pointer intrinsics
+
+# TODO: can we use constant propagation instead of passing the alignment as a Val?
+
+using Core: LLVMPtr
+
+function tbaa_make_child(name::String, constant::Bool=false; ctx::LLVM.Context=JuliaContext())
+    tbaa_root = MDNode([MDString("custom_tbaa", ctx)], ctx)
+    tbaa_struct_type =
+        MDNode([MDString("custom_tbaa_$name", ctx),
+                tbaa_root,
+                LLVM.ConstantInt(0, ctx)], ctx)
+    tbaa_access_tag =
+        MDNode([tbaa_struct_type,
+                tbaa_struct_type,
+                LLVM.ConstantInt(0, ctx),
+                LLVM.ConstantInt(constant ? 1 : 0, ctx)], ctx)
+
+    return tbaa_access_tag
+end
+
+tbaa_addrspace(as) = tbaa_make_child("addrspace($(as))")
+
+@generated function pointerref(ptr::LLVMPtr{T,A}, i::Int, ::Val{align}) where {T,A,align}
+    sizeof(T) == 0 && return T.instance
+    eltyp = convert(LLVMType, T)
+
+    T_int = convert(LLVMType, Int)
+    T_ptr = convert(LLVMType, ptr)
+
+    T_typed_ptr = LLVM.PointerType(eltyp, A)
+
+    # create a function
+    param_types = [T_ptr, T_int]
+    llvm_f, _ = create_function(eltyp, param_types)
+
+    # generate IR
+    Builder(JuliaContext()) do builder
+        entry = BasicBlock(llvm_f, "entry", JuliaContext())
+        position!(builder, entry)
+
+        typed_ptr = bitcast!(builder, parameters(llvm_f)[1], T_typed_ptr)
+        typed_ptr = gep!(builder, typed_ptr, [parameters(llvm_f)[2]])
+        ld = load!(builder, typed_ptr)
+
+        if A != 0
+            metadata(ld)[LLVM.MD_tbaa] = tbaa_addrspace(A)
+        end
+        alignment!(ld, align)
+
+        ret!(builder, ld)
+    end
+
+    call_function(llvm_f, T, Tuple{LLVMPtr{T,A}, Int}, :((ptr, Int(i-one(i)))))
+end
+
+@generated function pointerset(ptr::LLVMPtr{T,A}, x::T, i::Int, ::Val{align}) where {T,A,align}
+    sizeof(T) == 0 && return
+    eltyp = convert(LLVMType, T)
+
+    T_int = convert(LLVMType, Int)
+    T_ptr = convert(LLVMType, ptr)
+
+    T_typed_ptr = LLVM.PointerType(eltyp, A)
+
+    # create a function
+    param_types = [T_ptr, eltyp, T_int]
+    llvm_f, _ = create_function(LLVM.VoidType(JuliaContext()), param_types)
+
+    # generate IR
+    Builder(JuliaContext()) do builder
+        entry = BasicBlock(llvm_f, "entry", JuliaContext())
+        position!(builder, entry)
+
+        typed_ptr = bitcast!(builder, parameters(llvm_f)[1], T_typed_ptr)
+        typed_ptr = gep!(builder, typed_ptr, [parameters(llvm_f)[3]])
+        val = parameters(llvm_f)[2]
+        st = store!(builder, val, typed_ptr)
+
+        if A != 0
+            metadata(st)[LLVM.MD_tbaa] = tbaa_addrspace(A)
+        end
+        alignment!(st, align)
+
+        ret!(builder)
+    end
+
+    call_function(llvm_f, Cvoid, Tuple{LLVMPtr{T,A}, T, Int},
+                  :((ptr, convert(T,x), Int(i-one(i)))))
+end
+
+Base.unsafe_load(ptr::Core.LLVMPtr, i::Integer=1, align::Val=Val(1)) =
+    pointerref(ptr, Int(i), align)
+
+Base.unsafe_store!(ptr::Core.LLVMPtr{T}, x, i::Integer=1, align::Val=Val(1)) where {T} =
+    pointerset(ptr, convert(T, x), Int(i), align)

test/interop.jl

@@ -1,4 +1,5 @@
 using LLVM.Interop
+using InteractiveUtils
 
 @testset "interop" begin
 
@@ -126,4 +127,58 @@ end
 end
 end
 
+VERSION >= v"1.5-" && @testset "pointer" begin
+
+a = Int64[1]
+ptr = reinterpret(Core.LLVMPtr{Int64,0}, pointer(a))
+@test unsafe_load(ptr) == 1
+unsafe_store!(ptr, 2)
+@test unsafe_load(ptr) == 2
+
+ir = sprint(io->code_llvm(io, unsafe_load, Tuple{typeof(ptr)}))
+@test contains(ir, r"@julia_unsafe_load_\d+\(i8\*\)")
+@test contains(ir, r"load i64, i64\* %\d+, align 1")
+
+ir = sprint(io->code_llvm(io, unsafe_load, Tuple{typeof(ptr), Int, Val{4}}))
+@test contains(ir, r"load i64, i64\* %\d+, align 4")
+
+@testset "reinterpret(Nothing, nothing)" begin
+    ptr = reinterpret(Core.LLVMPtr{Nothing,0}, C_NULL)
+    @test unsafe_load(ptr) === nothing
+end
+
+@testset "TBAA" begin
+    load(ptr) = unsafe_load(ptr)
+    store(ptr) = unsafe_store!(ptr, 0)
+
+    for f in (load, store)
+        ir = sprint(io->code_llvm(io, f,
+                                  Tuple{Core.LLVMPtr{Float32,1}};
+                                  dump_module=true, raw=true))
+        @test occursin("custom_tbaa_addrspace(1)", ir)
+
+        # no TBAA on generic pointers
+        ir = sprint(io->code_llvm(io, f,
+                                  Tuple{Core.LLVMPtr{Float32,0}};
+                                  dump_module=true, raw=true))
+        @test !occursin("custom_tbaa", ir)
+    end
+end
+
+@testset "ghost values" begin
+    @eval struct Singleton end
+
+    ir = sprint(io->code_llvm(io, unsafe_load,
+                              Tuple{Core.LLVMPtr{Singleton,0}}))
+    @test occursin("ret void", ir)
+    @test unsafe_load(reinterpret(Core.LLVMPtr{Singleton,0}, C_NULL)) === Singleton()
+
+    ir = sprint(io->code_llvm(io, unsafe_store!,
+                              Tuple{Core.LLVMPtr{Singleton,0},
+                              Singleton}))
+    @test !occursin("\bstore\b", ir)
+end
+
+end
+
 end