stage2: generate a switch for `@errSetCast` safety

2 files changed, 49 insertions, 0 deletions

diff --git a/src/codegen/c.zig b/src/codegen/c.zig
index 74e4404bce..81a892183f 100644
--- a/src/codegen/c.zig
+++ b/src/codegen/c.zig
@@ -1954,6 +1954,7 @@ fn genBody(f: *Function, body: []const Air.Inst.Index) error{ AnalysisFail, OutO
             => return f.fail("TODO implement optimized float mode", .{}),
 
             .is_named_enum_value => return f.fail("TODO: C backend: implement is_named_enum_value", .{}),
+            .error_set_has_value => return f.fail("TODO: C backend: implement error_set_has_value", .{}),
             // zig fmt: on
         };
         switch (result_value) {
diff --git a/src/codegen/llvm.zig b/src/codegen/llvm.zig
index 38f7d285ae..5da3e7e327 100644
--- a/src/codegen/llvm.zig
+++ b/src/codegen/llvm.zig
@@ -4247,6 +4247,7 @@ pub const FuncGen = struct {
                 .prefetch       => try self.airPrefetch(inst),
 
                 .is_named_enum_value => try self.airIsNamedEnumValue(inst),
+                .error_set_has_value => try self.airErrorSetHasValue(inst),
 
                 .reduce           => try self.airReduce(inst, false),
                 .reduce_optimized => try self.airReduce(inst, true),
@@ -7983,6 +7984,53 @@ pub const FuncGen = struct {
         }
     }
 
+    fn airErrorSetHasValue(self: *FuncGen, inst: Air.Inst.Index) !?*const llvm.Value {
+        if (self.liveness.isUnused(inst)) return null;
+
+        const ty_op = self.air.instructions.items(.data)[inst].ty_op;
+        const operand = try self.resolveInst(ty_op.operand);
+        const error_set_ty = self.air.getRefType(ty_op.ty);
+
+        const names = error_set_ty.errorSetNames();
+        const valid_block = self.dg.context.appendBasicBlock(self.llvm_func, "Valid");
+        const invalid_block = self.dg.context.appendBasicBlock(self.llvm_func, "Invalid");
+        const end_block = self.context.appendBasicBlock(self.llvm_func, "End");
+        const switch_instr = self.builder.buildSwitch(operand, invalid_block, @intCast(c_uint, names.len));
+
+        for (names) |name| {
+            const err_int = self.dg.module.global_error_set.get(name).?;
+            const this_tag_int_value = int: {
+                var tag_val_payload: Value.Payload.U64 = .{
+                    .base = .{ .tag = .int_u64 },
+                    .data = err_int,
+                };
+                break :int try self.dg.lowerValue(.{
+                    .ty = Type.u16,
+                    .val = Value.initPayload(&tag_val_payload.base),
+                });
+            };
+            switch_instr.addCase(this_tag_int_value, valid_block);
+        }
+        self.builder.positionBuilderAtEnd(valid_block);
+        _ = self.builder.buildBr(end_block);
+
+        self.builder.positionBuilderAtEnd(invalid_block);
+        _ = self.builder.buildBr(end_block);
+
+        self.builder.positionBuilderAtEnd(end_block);
+
+        const llvm_type = self.dg.context.intType(1);
+        const incoming_values: [2]*const llvm.Value = .{
+            llvm_type.constInt(1, .False), llvm_type.constInt(0, .False),
+        };
+        const incoming_blocks: [2]*const llvm.BasicBlock = .{
+            valid_block, invalid_block,
+        };
+        const phi_node = self.builder.buildPhi(llvm_type, "");
+        phi_node.addIncoming(&incoming_values, &incoming_blocks, 2);
+        return phi_node;
+    }
+
     fn airIsNamedEnumValue(self: *FuncGen, inst: Air.Inst.Index) !?*const llvm.Value {
         if (self.liveness.isUnused(inst)) return null;