add custom handler for ptr_to_array runtime call (EnzymeAD#2258)

* add custom handler for ptr_to_array runtime call

* Update array.jl

* Update llvmrules.jl

---------

Co-authored-by: William Moses <[email protected]>

Author: vchuravy

src/compiler/validation.jl

@@ -78,11 +78,13 @@ function __init__()
         "jl_get_keyword_sorter",
         "ijl_get_keyword_sorter",
         "jl_ptr_to_array",
+        "ijl_ptr_to_array",
         "jl_box_float32",
         "ijl_box_float32",
         "jl_box_float64",
         "ijl_box_float64",
         "jl_ptr_to_array_1d",
+        "ijl_ptr_to_array_1d",
         "jl_eqtable_get",
         "ijl_eqtable_get",
         "memcmp",

src/rules/llvmrules.jl

@@ -1779,6 +1779,57 @@ end
     return nothing
 end
 
+@register_fwd function jl_ptr_to_array_fwd(B, orig, gutils, normalR, shadowR)
+    if is_constant_inst(gutils, orig)
+        return true
+    end
+    origops = collect(operands(orig))
+    width = get_width(gutils)
+    shadowin = invert_pointer(gutils, origops[2], B)
+
+    valTys = API.CValueType[
+        API.VT_Primal,
+        API.VT_Shadow,
+        API.VT_Primal,
+        API.VT_Primal,
+    ]
+
+    shadowres = UndefValue(LLVM.LLVMType(API.EnzymeGetShadowType(width, value_type(orig))))
+    for idx = 1:width
+        ev = if width == 1
+            shadowin
+        else
+            extract_value!(B, shadowin, idx - 1)
+        end
+
+	args = LLVM.Value[
+	        new_from_original(gutils, origops[1]),
+	        ev, # data
+	        new_from_original(gutils, origops[3]),
+	        new_from_original(gutils, origops[4]),
+	]
+	# TODO do runtime activity relevant errors and checks
+
+        cal = call_samefunc_with_inverted_bundles!(B, gutils, orig, args, valTys, false) #=lookup=#
+        debug_from_orig!(gutils, cal, orig)
+        callconv!(cal, callconv(orig))
+	if width == 1
+	    shadowres = cal
+	else
+            shadowres = insert_value!(B, shadowres, call, idx - 1)
+	end
+    end
+    unsafe_store!(shadowR, shadowres.ref)
+
+    return false
+end
+@register_aug function jl_ptr_to_array_augfwd(B, orig, gutils, normalR, shadowR, tapeR)
+    jl_ptr_to_array_fwd(B, orig, gutils, normalR, shadowR)
+end
+@register_rev function jl_ptr_to_array_rev(B, orig, gutils, tape)
+    return nothing
+end
+
 @register_fwd function genericmemory_copyto_fwd(B, orig, gutils, normalR, shadowR)
     if is_constant_inst(gutils, orig)
         return true
@@ -2400,6 +2451,12 @@ end
         @revfunc(jl_array_ptr_copy_rev),
         @fwdfunc(jl_array_ptr_copy_fwd),
     )
+    register_handler!(
+        ("jl_ptr_to_array_1d", "ijl_ptr_to_array_1d", "jl_ptr_to_array", "ijl_ptr_to_array"),
+        @augfunc(jl_ptr_to_array_augfwd),
+        @revfunc(jl_ptr_to_array_rev),
+        @fwdfunc(jl_ptr_to_array_fwd),
+    )
     register_handler!(
         (),
         @augfunc(jl_unhandled_augfwd),

test/array.jl

@@ -23,3 +23,18 @@ end
 	@test dB[1] === dA1
 	@test dB[2] === dA2
 end
+
+function unsafe_wrap_test(a, i, x)
+	GC.@preserve a begin
+		 ptr = pointer(a)
+		 b = Base.unsafe_wrap(Array, ptr, length(a))
+		 b[i] = x
+	end
+	a[i]
+end
+
+@testset "Unsafe wrap" begin
+   autodiff(Forward, unsafe_wrap_test,  Duplicated(zeros(1), zeros(1)), Const(1), Duplicated(1.0, 2.0))
+
+	# TODO test for batch and reverse
+end