Add generated Interop.addrspacecast for LLVMPtr (#322)

Base's reinterpret only calls bitcast, which is insufficient when the
source and destination pointers have different address spaces.

Co-authored-by: Valentin Churavy <[email protected]>

Author: jpsamaroo

src/interop/pointer.jl

@@ -114,6 +114,31 @@ Base.:(+)(x::Integer, y::LLVMPtr) = y + x
 Base.unsigned(x::LLVMPtr) = UInt(x)
 Base.signed(x::LLVMPtr) = Int(x)
 
+@generated function addrspacecast(::Type{LLVMPtr{TDest, ASDest}}, src::LLVMPtr{TSrc, ASSrc}) where {TDest, ASDest, TSrc, ASSrc}
+    @dispose ctx=Context() begin
+        T_dest = convert(LLVMType, LLVMPtr{TDest, ASDest}; ctx)
+        T_src = convert(LLVMType, LLVMPtr{TSrc, ASSrc}; ctx)
+
+        llvm_f, _ = create_function(T_dest, [T_src])
+        mod = LLVM.parent(llvm_f)
+
+        @dispose builder=Builder(ctx) begin
+            entry = BasicBlock(llvm_f, "entry"; ctx)
+            position!(builder, entry)
+
+            dest_ptr = if ASDest != ASSrc
+                addrspacecast!(builder, parameters(llvm_f)[1], T_dest)
+            else
+                parameters(llvm_f)[1]
+            end
+            ret!(builder, bitcast!(builder, dest_ptr, T_dest))
+        end
+
+        call_function(llvm_f, LLVMPtr{TDest, ASDest},
+                      Tuple{LLVMPtr{TSrc, ASSrc}}, :src)
+    end
+end
+
 
 # type-preserving ccall
 

test/interop.jl

@@ -202,6 +202,19 @@ end
     @test contains(ir, r"load i64, i64\* %\d+, align 4")
 end
 
+@testset "reinterpret with addrspacecast" begin
+    ptr = reinterpret(Core.LLVMPtr{Int64, 4}, 0)
+    for eltype_dest in (Int64, Int32), AS_dest in (4, 3)
+        T_dest = Core.LLVMPtr{eltype_dest, AS_dest}
+        ir = sprint(io->code_llvm(io, LLVM.Interop.addrspacecast, Tuple{Type{T_dest}, typeof(ptr)}))
+        if AS_dest == 3
+            @test contains(ir, r"addrspacecast i8 addrspace\(4\)\* %\d+ to i8 addrspace\(3\)\*")
+        else
+            @test !contains(ir, r"addrspacecast i8 addrspace\(4\)\* %\d+ to i8 addrspace\(3\)\*")
+        end
+    end
+end
+
 @testset "reinterpret(Nothing, nothing)" begin
     ptr = reinterpret(Core.LLVMPtr{Nothing,0}, C_NULL)
     @test unsafe_load(ptr) === nothing