From 6c16465d45527c195302beb1f3a1a6d41cdcdd92 Mon Sep 17 00:00:00 2001
From: Robin Voetter <robin@voetter.nl>
Date: Tue, 11 Apr 2023 22:29:02 +0200
Subject: [PATCH] spirv: lower air optional_payload

Implements lowering the AIR tag optional_payload.

Also fixes an issue with lowering constant ints.
---
 src/codegen/spirv.zig | 29 ++++++++++++++++++++++++-----
 1 file changed, 24 insertions(+), 5 deletions(-)

diff --git a/src/codegen/spirv.zig b/src/codegen/spirv.zig
index 0388466c10..ab2bdd64a7 100644
--- a/src/codegen/spirv.zig
+++ b/src/codegen/spirv.zig
@@ -957,11 +957,11 @@ pub const DeclGen = struct {
 
         switch (ty.zigTypeTag()) {
             .Int => {
-                const int_bits = if (ty.isSignedInt())
-                    @bitCast(u64, val.toSignedInt(target))
-                else
-                    val.toUnsignedInt(target);
-                try self.genConstInt(result_ty_ref, result_id, int_bits);
+                if (ty.isSignedInt()) {
+                    try self.genConstInt(result_ty_ref, result_id, val.toSignedInt(target));
+                } else {
+                    try self.genConstInt(result_ty_ref, result_id, val.toUnsignedInt(target));
+                }
             },
             .Bool => {
                 const operands = .{ .id_result_type = result_ty_id, .id_result = result_id };
@@ -1717,6 +1717,8 @@ pub const DeclGen = struct {
             .is_null     => try self.airIsNull(inst, .is_null),
             .is_non_null => try self.airIsNull(inst, .is_non_null),
 
+            .optional_payload => try self.airUnwrapOptional(inst),
+
             .assembly => try self.airAssembly(inst),
 
             .call              => try self.airCall(inst, .auto),
@@ -2694,6 +2696,23 @@ pub const DeclGen = struct {
         };
     }
 
+    fn airUnwrapOptional(self: *DeclGen, inst: Air.Inst.Index) !?IdRef {
+        if (self.liveness.isUnused(inst)) return null;
+
+        const ty_op = self.air.instructions.items(.data)[inst].ty_op;
+        const operand_id = try self.resolve(ty_op.operand);
+        const optional_ty = self.air.typeOf(ty_op.operand);
+        const payload_ty = self.air.typeOfIndex(inst);
+
+        if (!payload_ty.hasRuntimeBitsIgnoreComptime()) return null;
+
+        if (optional_ty.optionalReprIsPayload()) {
+            return operand_id;
+        }
+
+        return try self.extractField(payload_ty, operand_id, 0);
+    }
+
     fn airSwitchBr(self: *DeclGen, inst: Air.Inst.Index) !void {
         const target = self.getTarget();
         const pl_op = self.air.instructions.items(.data)[inst].pl_op;