stage2: improve LLVM backend for enums

 * support lowering enum types and constants to LLVM IR
 * fix cmp instruction to support enum operands

Author: andrewrk

src/codegen/llvm.zig

@@ -588,6 +588,12 @@ pub const DeclGen = struct {
                 const info = t.intInfo(self.module.getTarget());
                 return self.context.intType(info.bits);
             },
+            .Enum => {
+                var buffer: Type.Payload.Bits = undefined;
+                const int_ty = t.enumTagType(&buffer);
+                const bit_count = int_ty.intInfo(self.module.getTarget()).bits;
+                return self.context.intType(bit_count);
+            },
             .Float => switch (t.floatBits(self.module.getTarget())) {
                 16 => return self.context.halfType(),
                 32 => return self.context.floatType(),
@@ -686,7 +692,6 @@ pub const DeclGen = struct {
 
             .BoundFn => @panic("TODO remove BoundFn from the language"),
 
-            .Enum,
             .Union,
             .Opaque,
             .Frame,
@@ -723,6 +728,17 @@ pub const DeclGen = struct {
                 }
                 return llvm_int;
             },
+            .Enum => {
+                const llvm_type = try self.llvmType(tv.ty);
+                const uint: u64 = uint: {
+                    if (tv.val.castTag(.enum_field_index)) |payload| {
+                        break :uint payload.data;
+                    }
+                    break :uint tv.val.toUnsignedInt();
+                };
+                const llvm_int = llvm_type.constInt(uint, .False);
+                return llvm_int;
+            },
             .Float => {
                 if (tv.ty.floatBits(self.module.getTarget()) <= 64) {
                     const llvm_ty = try self.llvmType(tv.ty);
@@ -907,7 +923,18 @@ pub const DeclGen = struct {
             .ComptimeFloat => unreachable,
             .Type => unreachable,
             .EnumLiteral => unreachable,
-            else => return self.todo("implement const of type '{}'", .{tv.ty}),
+            .Void => unreachable,
+            .NoReturn => unreachable,
+            .Undefined => unreachable,
+            .Null => unreachable,
+            .BoundFn => unreachable,
+            .Opaque => unreachable,
+
+            .Union,
+            .Frame,
+            .AnyFrame,
+            .Vector,
+            => return self.todo("implement const of type '{}'", .{tv.ty}),
         }
     }
 
@@ -1195,21 +1222,15 @@ pub const FuncGen = struct {
         const bin_op = self.air.instructions.items(.data)[inst].bin_op;
         const lhs = try self.resolveInst(bin_op.lhs);
         const rhs = try self.resolveInst(bin_op.rhs);
-        const inst_ty = self.air.typeOfIndex(inst);
+        const operand_ty = self.air.typeOf(bin_op.lhs);
 
-        switch (self.air.typeOf(bin_op.lhs).zigTypeTag()) {
-            .Int, .Bool, .Pointer, .ErrorSet => {
-                const is_signed = inst_ty.isSignedInt();
-                const operation = switch (op) {
-                    .eq => .EQ,
-                    .neq => .NE,
-                    .lt => @as(llvm.IntPredicate, if (is_signed) .SLT else .ULT),
-                    .lte => @as(llvm.IntPredicate, if (is_signed) .SLE else .ULE),
-                    .gt => @as(llvm.IntPredicate, if (is_signed) .SGT else .UGT),
-                    .gte => @as(llvm.IntPredicate, if (is_signed) .SGE else .UGE),
-                };
-                return self.builder.buildICmp(operation, lhs, rhs, "");
+        const int_ty = switch (operand_ty.zigTypeTag()) {
+            .Enum => blk: {
+                var buffer: Type.Payload.Bits = undefined;
+                const int_ty = operand_ty.enumTagType(&buffer);
+                break :blk int_ty;
             },
+            .Int, .Bool, .Pointer, .ErrorSet => operand_ty,
             .Float => {
                 const operation: llvm.RealPredicate = switch (op) {
                     .eq => .OEQ,
@@ -1222,7 +1243,17 @@ pub const FuncGen = struct {
                 return self.builder.buildFCmp(operation, lhs, rhs, "");
             },
             else => unreachable,
-        }
+        };
+        const is_signed = int_ty.isSignedInt();
+        const operation = switch (op) {
+            .eq => .EQ,
+            .neq => .NE,
+            .lt => @as(llvm.IntPredicate, if (is_signed) .SLT else .ULT),
+            .lte => @as(llvm.IntPredicate, if (is_signed) .SLE else .ULE),
+            .gt => @as(llvm.IntPredicate, if (is_signed) .SGT else .UGT),
+            .gte => @as(llvm.IntPredicate, if (is_signed) .SGE else .UGE),
+        };
+        return self.builder.buildICmp(operation, lhs, rhs, "");
     }
 
     fn airBlock(self: *FuncGen, inst: Air.Inst.Index) !?*const llvm.Value {

test/behavior/atomics.zig

@@ -118,3 +118,15 @@ test "cmpxchg on a global variable" {
     _ = @cmpxchgWeak(u32, &a_global_variable, 1234, 42, .Acquire, .Monotonic);
     try expect(a_global_variable == 42);
 }
+
+test "atomic load and rmw with enum" {
+    const Value = enum(u8) { a, b, c };
+    var x = Value.a;
+
+    try expect(@atomicLoad(Value, &x, .SeqCst) != .b);
+
+    _ = @atomicRmw(Value, &x, .Xchg, .c, .SeqCst);
+    try expect(@atomicLoad(Value, &x, .SeqCst) == .c);
+    try expect(@atomicLoad(Value, &x, .SeqCst) != .a);
+    try expect(@atomicLoad(Value, &x, .SeqCst) != .b);
+}

test/behavior/atomics_stage1.zig

@@ -3,22 +3,6 @@ const expect = std.testing.expect;
 const expectEqual = std.testing.expectEqual;
 const builtin = @import("builtin");
 
-test "atomic load and rmw with enum" {
-    const Value = enum(u8) {
-        a,
-        b,
-        c,
-    };
-    var x = Value.a;
-
-    try expect(@atomicLoad(Value, &x, .SeqCst) != .b);
-
-    _ = @atomicRmw(Value, &x, .Xchg, .c, .SeqCst);
-    try expect(@atomicLoad(Value, &x, .SeqCst) == .c);
-    try expect(@atomicLoad(Value, &x, .SeqCst) != .a);
-    try expect(@atomicLoad(Value, &x, .SeqCst) != .b);
-}
-
 test "atomic store" {
     var x: u32 = 0;
     @atomicStore(u32, &x, 1, .SeqCst);