stage2: elemPtr for slices

* Restructure elemPtr a bit
* New AIR instruction: slice_elem_ptr, which returns a pointer to an element of a slice
* Value: adapt elemPtr to work on slices

1 files changed, 10 insertions, 0 deletions

diff --git a/src/codegen.zig b/src/codegen.zig
index 873260329c..5963cdd376 100644
--- a/src/codegen.zig
+++ b/src/codegen.zig
@@ -848,6 +848,7 @@ fn Function(comptime arch: std.Target.Cpu.Arch) type {
 
                     .array_elem_val      => try self.airArrayElemVal(inst),
                     .slice_elem_val      => try self.airSliceElemVal(inst),
+                    .slice_elem_ptr      => try self.airSliceElemPtr(inst),
                     .ptr_elem_val        => try self.airPtrElemVal(inst),
                     .ptr_elem_ptr        => try self.airPtrElemPtr(inst),
 
@@ -1533,6 +1534,15 @@ fn Function(comptime arch: std.Target.Cpu.Arch) type {
             return self.finishAir(inst, result, .{ bin_op.lhs, bin_op.rhs, .none });
         }
 
+        fn airSliceElemPtr(self: *Self, inst: Air.Inst.Index) !void {
+            const ty_pl = self.air.instructions.items(.data)[inst].ty_pl;
+            const extra = self.air.extraData(Air.Bin, ty_pl.payload).data;
+            const result: MCValue = if (self.liveness.isUnused(inst)) .dead else switch (arch) {
+                else => return self.fail("TODO implement slice_elem_ptr for {}", .{self.target.cpu.arch}),
+            };
+            return self.finishAir(inst, result, .{ extra.lhs, extra.rhs, .none });
+        }
+
         fn airArrayElemVal(self: *Self, inst: Air.Inst.Index) !void {
             const bin_op = self.air.instructions.items(.data)[inst].bin_op;
             const result: MCValue = if (self.liveness.isUnused(inst)) .dead else switch (arch) {