Sema: implement coerce_result_ptr for optionals

New AIR instruction: `optional_payload_ptr_set`
It's like `optional_payload_ptr` except it sets the non-null bit.

When storing to the payload via a result location that is an optional,
`optional_payload_ptr_set` is now emitted. There is a new algorithm in
`zirCoerceResultPtr` which stores a dummy value through the result
pointer into a temporary block, and then pops off the AIR instructions
from the temporary block in order to determine how to transform the
result location pointer in case any in-between coercions need to happen.

Fixes a couple of behavior tests regarding optionals.

1 files changed, 7 insertions, 0 deletions

diff --git a/src/arch/arm/CodeGen.zig b/src/arch/arm/CodeGen.zig
index 0bf6fd2b83..0aad12e8b7 100644
--- a/src/arch/arm/CodeGen.zig
+++ b/src/arch/arm/CodeGen.zig
@@ -510,6 +510,7 @@ fn genBody(self: *Self, body: []const Air.Inst.Index) InnerError!void {
 
                     .optional_payload           => try self.airOptionalPayload(inst),
                     .optional_payload_ptr       => try self.airOptionalPayloadPtr(inst),
+                    .optional_payload_ptr_set   => try self.airOptionalPayloadPtrSet(inst),
                     .unwrap_errunion_err        => try self.airUnwrapErrErr(inst),
                     .unwrap_errunion_payload    => try self.airUnwrapErrPayload(inst),
                     .unwrap_errunion_err_ptr    => try self.airUnwrapErrErrPtr(inst),
@@ -1008,6 +1009,12 @@ fn airOptionalPayloadPtr(self: *Self, inst: Air.Inst.Index) !void {
     return self.finishAir(inst, result, .{ ty_op.operand, .none, .none });
 }
 
+fn airOptionalPayloadPtrSet(self: *Self, inst: Air.Inst.Index) !void {
+    const ty_op = self.air.instructions.items(.data)[inst].ty_op;
+    const result: MCValue = if (self.liveness.isUnused(inst)) .dead else return self.fail("TODO implement .optional_payload_ptr_set for {}", .{self.target.cpu.arch});
+    return self.finishAir(inst, result, .{ ty_op.operand, .none, .none });
+}
+
 fn airUnwrapErrErr(self: *Self, inst: Air.Inst.Index) !void {
     const ty_op = self.air.instructions.items(.data)[inst].ty_op;
     const result: MCValue = if (self.liveness.isUnused(inst)) .dead else return self.fail("TODO implement unwrap error union error for {}", .{self.target.cpu.arch});