Merge pull request #11120 from Vexu/stage2

Stage2: make std.rand tests pass

12 files changed, 392 insertions, 19 deletions

diff --git a/src/Air.zig b/src/Air.zig
index cc15113653..a1d5e1e8d9 100644
--- a/src/Air.zig
+++ b/src/Air.zig
@@ -520,6 +520,9 @@ pub const Inst = struct {
         /// equal to the scalar value.
         /// Uses the `ty_op` field.
         splat,
+        /// Constructs a vector by selecting elements from `a` and `b` based on `mask`.
+        /// Uses the `ty_pl` field with payload `Shuffle`.
+        shuffle,
 
         /// Given dest ptr, value, and len, set all elements at dest to value.
         /// Result type is always void.
@@ -740,6 +743,14 @@ pub const FieldParentPtr = struct {
     field_index: u32,
 };
 
+pub const Shuffle = struct {
+    a: Inst.Ref,
+    b: Inst.Ref,
+    // index to air_values
+    mask: u32,
+    mask_len: u32,
+};
+
 /// Trailing:
 /// 0. `Inst.Ref` for every outputs_len
 /// 1. `Inst.Ref` for every inputs_len
@@ -897,6 +908,7 @@ pub fn typeOfIndex(air: Air, inst: Air.Inst.Index) Type {
         .cmpxchg_weak,
         .cmpxchg_strong,
         .slice,
+        .shuffle,
         .aggregate_init,
         .union_init,
         .field_parent_ptr,
diff --git a/src/Liveness.zig b/src/Liveness.zig
index 077d2f2888..c91288f354 100644
--- a/src/Liveness.zig
+++ b/src/Liveness.zig
@@ -422,6 +422,10 @@ fn analyzeInst(
             }
             return extra_tombs.finish();
         },
+        .shuffle => {
+            const extra = a.air.extraData(Air.Shuffle, inst_datas[inst].ty_pl.payload).data;
+            return trackOperands(a, new_set, inst, main_tomb, .{ extra.a, extra.b, .none });
+        },
         .aggregate_init => {
             const ty_pl = inst_datas[inst].ty_pl;
             const aggregate_ty = a.air.getRefType(ty_pl.ty);
diff --git a/src/Sema.zig b/src/Sema.zig
index 2a3236e8ad..a33861c74c 100644
--- a/src/Sema.zig
+++ b/src/Sema.zig
@@ -4618,7 +4618,7 @@ fn analyzeCall(
                         },
                         else => {},
                     }
-                    should_memoize = should_memoize and !arg_val.isComptimeMutablePtr();
+                    should_memoize = should_memoize and !arg_val.canMutateComptimeVarState();
                     memoized_call_key.args[arg_i] = .{
                         .ty = param_ty,
                         .val = arg_val,
@@ -4644,7 +4644,7 @@ fn analyzeCall(
                         },
                         else => {},
                     }
-                    should_memoize = should_memoize and !arg_val.isComptimeMutablePtr();
+                    should_memoize = should_memoize and !arg_val.canMutateComptimeVarState();
                     memoized_call_key.args[arg_i] = .{
                         .ty = sema.typeOf(uncasted_arg),
                         .val = arg_val,
@@ -5923,6 +5923,10 @@ fn funcCommon(
                     break :ret_ty ret_ty;
                 } else |err| break :err err;
             } else |err| break :err err;
+            // Check for generic params.
+            for (block.params.items) |param| {
+                if (param.ty.tag() == .generic_poison) is_generic = true;
+            }
         };
         switch (err) {
             error.GenericPoison => {
@@ -6111,6 +6115,13 @@ fn zirParam(
 
             if (sema.resolveBody(block, body, inst)) |param_ty_inst| {
                 if (sema.analyzeAsType(block, src, param_ty_inst)) |param_ty| {
+                    if (param_ty.zigTypeTag() == .Fn and param_ty.fnInfo().is_generic) {
+                        // zirFunc will not emit error.GenericPoison to build a
+                        // partial type for generic functions but we still need to
+                        // detect if a function parameter is a generic function
+                        // to force the parent function to also be generic.
+                        break :err error.GenericPoison;
+                    }
                     break :param_ty param_ty;
                 } else |err| break :err err;
             } else |err| break :err err;
@@ -8048,7 +8059,6 @@ fn zirBitwise(
                 rhs_ty.arrayLen(),
             });
         }
-        return sema.fail(block, src, "TODO implement support for vectors in zirBitwise", .{});
     } else if (lhs_ty.zigTypeTag() == .Vector or rhs_ty.zigTypeTag() == .Vector) {
         return sema.fail(block, src, "mixed scalar and vector operands to binary expression: '{}' and '{}'", .{
             lhs_ty,
@@ -8064,6 +8074,9 @@ fn zirBitwise(
 
     if (try sema.resolveMaybeUndefVal(block, lhs_src, casted_lhs)) |lhs_val| {
         if (try sema.resolveMaybeUndefVal(block, rhs_src, casted_rhs)) |rhs_val| {
+            if (resolved_type.zigTypeTag() == .Vector) {
+                return sema.fail(block, src, "TODO implement zirBitwise for vectors at comptime", .{});
+            }
             const result_val = switch (air_tag) {
                 .bit_and => try lhs_val.bitwiseAnd(rhs_val, sema.arena),
                 .bit_or => try lhs_val.bitwiseOr(rhs_val, sema.arena),
@@ -10965,6 +10978,7 @@ fn zirTypeofBuiltin(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileErr
 
     const operand = try sema.resolveBody(&child_block, body, inst);
     const operand_ty = sema.typeOf(operand);
+    if (operand_ty.tag() == .generic_poison) return error.GenericPoison;
     return sema.addType(operand_ty);
 }
 
@@ -10973,19 +10987,21 @@ fn zirTypeofLog2IntType(sema: *Sema, block: *Block, inst: Zir.Inst.Index) Compil
     const src = inst_data.src();
     const operand = sema.resolveInst(inst_data.operand);
     const operand_ty = sema.typeOf(operand);
-    return sema.log2IntType(block, operand_ty, src);
+    const res_ty = try sema.log2IntType(block, operand_ty, src);
+    return sema.addType(res_ty);
 }
 
 fn zirLog2IntType(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileError!Air.Inst.Ref {
     const inst_data = sema.code.instructions.items(.data)[inst].un_node;
     const src = inst_data.src();
     const operand = try sema.resolveType(block, src, inst_data.operand);
-    return sema.log2IntType(block, operand, src);
+    const res_ty = try sema.log2IntType(block, operand, src);
+    return sema.addType(res_ty);
 }
 
-fn log2IntType(sema: *Sema, block: *Block, operand: Type, src: LazySrcLoc) CompileError!Air.Inst.Ref {
+fn log2IntType(sema: *Sema, block: *Block, operand: Type, src: LazySrcLoc) CompileError!Type {
     switch (operand.zigTypeTag()) {
-        .ComptimeInt => return Air.Inst.Ref.comptime_int_type,
+        .ComptimeInt => return Type.@"comptime_int",
         .Int => {
             const bits = operand.bitSize(sema.mod.getTarget());
             const count = if (bits == 0)
@@ -10998,16 +11014,24 @@ fn log2IntType(sema: *Sema, block: *Block, operand: Type, src: LazySrcLoc) Compi
                 }
                 break :blk count;
             };
-            const res = try Module.makeIntType(sema.arena, .unsigned, count);
-            return sema.addType(res);
+            return Module.makeIntType(sema.arena, .unsigned, count);
         },
-        else => return sema.fail(
-            block,
-            src,
-            "bit shifting operation expected integer type, found '{}'",
-            .{operand},
-        ),
+        .Vector => {
+            const elem_ty = operand.elemType2();
+            const log2_elem_ty = try sema.log2IntType(block, elem_ty, src);
+            return Type.Tag.vector.create(sema.arena, .{
+                .len = operand.arrayLen(),
+                .elem_type = log2_elem_ty,
+            });
+        },
+        else => {},
     }
+    return sema.fail(
+        block,
+        src,
+        "bit shifting operation expected integer type, found '{}'",
+        .{operand},
+    );
 }
 
 fn zirTypeofPeer(
@@ -11044,6 +11068,7 @@ fn zirTypeofPeer(
 
     for (args) |arg_ref, i| {
         inst_list[i] = sema.resolveInst(arg_ref);
+        if (sema.typeOf(inst_list[i]).tag() == .generic_poison) return error.GenericPoison;
     }
 
     const result_type = try sema.resolvePeerTypes(block, src, inst_list, .{ .typeof_builtin_call_node_offset = extra.data.src_node });
@@ -13427,8 +13452,193 @@ fn zirReduce(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileError!Air.
 
 fn zirShuffle(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileError!Air.Inst.Ref {
     const inst_data = sema.code.instructions.items(.data)[inst].pl_node;
-    const src = inst_data.src();
-    return sema.fail(block, src, "TODO: Sema.zirShuffle", .{});
+    const extra = sema.code.extraData(Zir.Inst.Shuffle, inst_data.payload_index).data;
+    const elem_ty_src: LazySrcLoc = .{ .node_offset_builtin_call_arg0 = inst_data.src_node };
+    const mask_src: LazySrcLoc = .{ .node_offset_builtin_call_arg3 = inst_data.src_node };
+
+    const elem_ty = try sema.resolveType(block, elem_ty_src, extra.elem_type);
+    try sema.checkVectorElemType(block, elem_ty_src, elem_ty);
+    var a = sema.resolveInst(extra.a);
+    var b = sema.resolveInst(extra.b);
+    var mask = sema.resolveInst(extra.mask);
+    var mask_ty = sema.typeOf(mask);
+
+    const mask_len = switch (sema.typeOf(mask).zigTypeTag()) {
+        .Array, .Vector => sema.typeOf(mask).arrayLen(),
+        else => return sema.fail(block, mask_src, "expected vector or array, found {}", .{sema.typeOf(mask)}),
+    };
+    mask_ty = try Type.Tag.vector.create(sema.arena, .{
+        .len = mask_len,
+        .elem_type = Type.@"i32",
+    });
+    mask = try sema.coerce(block, mask_ty, mask, mask_src);
+    const mask_val = try sema.resolveConstMaybeUndefVal(block, mask_src, mask);
+    return sema.analyzeShuffle(block, inst_data.src_node, elem_ty, a, b, mask_val, @intCast(u32, mask_len));
+}
+
+fn analyzeShuffle(
+    sema: *Sema,
+    block: *Block,
+    src_node: i32,
+    elem_ty: Type,
+    a_arg: Air.Inst.Ref,
+    b_arg: Air.Inst.Ref,
+    mask: Value,
+    mask_len: u32,
+) CompileError!Air.Inst.Ref {
+    const a_src: LazySrcLoc = .{ .node_offset_builtin_call_arg1 = src_node };
+    const b_src: LazySrcLoc = .{ .node_offset_builtin_call_arg2 = src_node };
+    const mask_src: LazySrcLoc = .{ .node_offset_builtin_call_arg3 = src_node };
+    var a = a_arg;
+    var b = b_arg;
+
+    const res_ty = try Type.Tag.vector.create(sema.arena, .{
+        .len = mask_len,
+        .elem_type = elem_ty,
+    });
+
+    var maybe_a_len = switch (sema.typeOf(a).zigTypeTag()) {
+        .Array, .Vector => sema.typeOf(a).arrayLen(),
+        .Undefined => null,
+        else => return sema.fail(block, a_src, "expected vector or array with element type {}, found {}", .{
+            elem_ty,
+            sema.typeOf(a),
+        }),
+    };
+    var maybe_b_len = switch (sema.typeOf(b).zigTypeTag()) {
+        .Array, .Vector => sema.typeOf(b).arrayLen(),
+        .Undefined => null,
+        else => return sema.fail(block, b_src, "expected vector or array with element type {}, found {}", .{
+            elem_ty,
+            sema.typeOf(b),
+        }),
+    };
+    if (maybe_a_len == null and maybe_b_len == null) {
+        return sema.addConstUndef(res_ty);
+    }
+    const a_len = maybe_a_len orelse maybe_b_len.?;
+    const b_len = maybe_b_len orelse a_len;
+
+    const a_ty = try Type.Tag.vector.create(sema.arena, .{
+        .len = a_len,
+        .elem_type = elem_ty,
+    });
+    const b_ty = try Type.Tag.vector.create(sema.arena, .{
+        .len = b_len,
+        .elem_type = elem_ty,
+    });
+
+    if (maybe_a_len == null) a = try sema.addConstUndef(a_ty);
+    if (maybe_b_len == null) b = try sema.addConstUndef(b_ty);
+
+    const operand_info = [2]std.meta.Tuple(&.{ u64, LazySrcLoc, Type }){
+        .{ a_len, a_src, a_ty },
+        .{ b_len, b_src, b_ty },
+    };
+
+    var i: usize = 0;
+    while (i < mask_len) : (i += 1) {
+        var buf: Value.ElemValueBuffer = undefined;
+        const elem = mask.elemValueBuffer(i, &buf);
+        if (elem.isUndef()) continue;
+        const int = elem.toSignedInt();
+        var unsigned: u32 = undefined;
+        var chosen: u32 = undefined;
+        if (int >= 0) {
+            unsigned = @intCast(u32, int);
+            chosen = 0;
+        } else {
+            unsigned = @intCast(u32, ~int);
+            chosen = 1;
+        }
+        if (unsigned >= operand_info[chosen][0]) {
+            const msg = msg: {
+                const msg = try sema.errMsg(block, mask_src, "mask index {d} has out-of-bounds selection", .{i});
+                errdefer msg.destroy(sema.gpa);
+
+                try sema.errNote(block, operand_info[chosen][1], msg, "selected index {d} out of bounds of {}", .{
+                    unsigned,
+                    operand_info[chosen][2],
+                });
+
+                if (chosen == 1) {
+                    try sema.errNote(block, b_src, msg, "selections from the second vector are specified with negative numbers", .{});
+                }
+
+                break :msg msg;
+            };
+            return sema.failWithOwnedErrorMsg(block, msg);
+        }
+    }
+
+    if (try sema.resolveMaybeUndefVal(block, a_src, a)) |a_val| {
+        if (try sema.resolveMaybeUndefVal(block, b_src, b)) |b_val| {
+            const values = try sema.arena.alloc(Value, mask_len);
+
+            i = 0;
+            while (i < mask_len) : (i += 1) {
+                var buf: Value.ElemValueBuffer = undefined;
+                const mask_elem_val = mask.elemValueBuffer(i, &buf);
+                if (mask_elem_val.isUndef()) {
+                    values[i] = Value.undef;
+                    continue;
+                }
+                const int = mask_elem_val.toSignedInt();
+                const unsigned = if (int >= 0) @intCast(u32, int) else @intCast(u32, ~int);
+                if (int >= 0) {
+                    values[i] = try a_val.elemValue(sema.arena, unsigned);
+                } else {
+                    values[i] = try b_val.elemValue(sema.arena, unsigned);
+                }
+            }
+            const res_val = try Value.Tag.array.create(sema.arena, values);
+            return sema.addConstant(res_ty, res_val);
+        }
+    }
+
+    // All static analysis passed, and not comptime.
+    // For runtime codegen, vectors a and b must be the same length. Here we
+    // recursively @shuffle the smaller vector to append undefined elements
+    // to it up to the length of the longer vector. This recursion terminates
+    // in 1 call because these calls to analyzeShuffle guarantee a_len == b_len.
+    if (a_len != b_len) {
+        const min_len = std.math.min(a_len, b_len);
+        const max_src = if (a_len > b_len) a_src else b_src;
+        const max_len = try sema.usizeCast(block, max_src, std.math.max(a_len, b_len));
+
+        const expand_mask_values = try sema.arena.alloc(Value, max_len);
+        i = 0;
+        while (i < min_len) : (i += 1) {
+            expand_mask_values[i] = try Value.Tag.int_u64.create(sema.arena, i);
+        }
+        while (i < max_len) : (i += 1) {
+            expand_mask_values[i] = Value.negative_one;
+        }
+        const expand_mask = try Value.Tag.array.create(sema.arena, expand_mask_values);
+
+        if (a_len < b_len) {
+            const undef = try sema.addConstUndef(a_ty);
+            a = try sema.analyzeShuffle(block, src_node, elem_ty, a, undef, expand_mask, @intCast(u32, max_len));
+        } else {
+            const undef = try sema.addConstUndef(b_ty);
+            b = try sema.analyzeShuffle(block, src_node, elem_ty, b, undef, expand_mask, @intCast(u32, max_len));
+        }
+    }
+
+    const mask_index = @intCast(u32, sema.air_values.items.len);
+    try sema.air_values.append(sema.gpa, mask);
+    return block.addInst(.{
+        .tag = .shuffle,
+        .data = .{ .ty_pl = .{
+            .ty = try sema.addType(res_ty),
+            .payload = try block.sema.addExtra(Air.Shuffle{
+                .a = a,
+                .b = b,
+                .mask = mask_index,
+                .mask_len = mask_len,
+            }),
+        } },
+    });
 }
 
 fn zirSelect(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileError!Air.Inst.Ref {
@@ -15663,8 +15873,7 @@ fn elemPtr(
                 },
             }
         },
-        .Array => return sema.elemPtrArray(block, array_ptr_src, array_ptr, elem_index, elem_index_src),
-        .Vector => return sema.fail(block, src, "TODO implement Sema for elemPtr for vector", .{}),
+        .Array, .Vector => return sema.elemPtrArray(block, array_ptr_src, array_ptr, elem_index, elem_index_src),
         .Struct => {
             // Tuple field access.
             const index_val = try sema.resolveConstValue(block, elem_index_src, elem_index);
diff --git a/src/arch/aarch64/CodeGen.zig b/src/arch/aarch64/CodeGen.zig
index dcac2c0a60..10e93cf23c 100644
--- a/src/arch/aarch64/CodeGen.zig
+++ b/src/arch/aarch64/CodeGen.zig
@@ -637,6 +637,7 @@ fn genBody(self: *Self, body: []const Air.Inst.Index) InnerError!void {
             .tag_name        => try self.airTagName(inst),
             .error_name      => try self.airErrorName(inst),
             .splat           => try self.airSplat(inst),
+            .shuffle         => try self.airShuffle(inst),
             .aggregate_init  => try self.airAggregateInit(inst),
             .union_init      => try self.airUnionInit(inst),
             .prefetch        => try self.airPrefetch(inst),
@@ -3633,6 +3634,12 @@ fn airSplat(self: *Self, inst: Air.Inst.Index) !void {
     return self.finishAir(inst, result, .{ ty_op.operand, .none, .none });
 }
 
+fn airShuffle(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 airShuffle for {}", .{self.target.cpu.arch});
+    return self.finishAir(inst, result, .{ ty_op.operand, .none, .none });
+}
+
 fn airAggregateInit(self: *Self, inst: Air.Inst.Index) !void {
     const vector_ty = self.air.typeOfIndex(inst);
     const len = vector_ty.vectorLen();
diff --git a/src/arch/arm/CodeGen.zig b/src/arch/arm/CodeGen.zig
index 2248daf1d0..e1eed9a941 100644
--- a/src/arch/arm/CodeGen.zig
+++ b/src/arch/arm/CodeGen.zig
@@ -636,6 +636,7 @@ fn genBody(self: *Self, body: []const Air.Inst.Index) InnerError!void {
             .tag_name        => try self.airTagName(inst),
             .error_name      => try self.airErrorName(inst),
             .splat           => try self.airSplat(inst),
+            .shuffle         => try self.airShuffle(inst),
             .aggregate_init  => try self.airAggregateInit(inst),
             .union_init      => try self.airUnionInit(inst),
             .prefetch        => try self.airPrefetch(inst),
@@ -4094,6 +4095,12 @@ fn airSplat(self: *Self, inst: Air.Inst.Index) !void {
     return self.finishAir(inst, result, .{ ty_op.operand, .none, .none });
 }
 
+fn airShuffle(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 airShuffle for arm", .{});
+    return self.finishAir(inst, result, .{ ty_op.operand, .none, .none });
+}
+
 fn airAggregateInit(self: *Self, inst: Air.Inst.Index) !void {
     const vector_ty = self.air.typeOfIndex(inst);
     const len = vector_ty.vectorLen();
diff --git a/src/arch/riscv64/CodeGen.zig b/src/arch/riscv64/CodeGen.zig
index 07903cebdc..f6a4b9c08e 100644
--- a/src/arch/riscv64/CodeGen.zig
+++ b/src/arch/riscv64/CodeGen.zig
@@ -603,6 +603,7 @@ fn genBody(self: *Self, body: []const Air.Inst.Index) InnerError!void {
             .tag_name        => try self.airTagName(inst),
             .error_name      => try self.airErrorName(inst),
             .splat           => try self.airSplat(inst),
+            .shuffle         => try self.airShuffle(inst),
             .aggregate_init  => try self.airAggregateInit(inst),
             .union_init      => try self.airUnionInit(inst),
             .prefetch        => try self.airPrefetch(inst),
@@ -2181,6 +2182,12 @@ fn airSplat(self: *Self, inst: Air.Inst.Index) !void {
     return self.finishAir(inst, result, .{ ty_op.operand, .none, .none });
 }
 
+fn airShuffle(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 airShuffle for riscv64", .{});
+    return self.finishAir(inst, result, .{ ty_op.operand, .none, .none });
+}
+
 fn airAggregateInit(self: *Self, inst: Air.Inst.Index) !void {
     const vector_ty = self.air.typeOfIndex(inst);
     const len = vector_ty.vectorLen();
diff --git a/src/arch/wasm/CodeGen.zig b/src/arch/wasm/CodeGen.zig
index 3f28b87b55..6c54699831 100644
--- a/src/arch/wasm/CodeGen.zig
+++ b/src/arch/wasm/CodeGen.zig
@@ -1255,6 +1255,7 @@ fn genInst(self: *Self, inst: Air.Inst.Index) !WValue {
         .ret_ptr => self.airRetPtr(inst),
         .ret_load => self.airRetLoad(inst),
         .splat => self.airSplat(inst),
+        .shuffle => self.airShuffle(inst),
         .aggregate_init => self.airAggregateInit(inst),
         .union_init => self.airUnionInit(inst),
         .prefetch => self.airPrefetch(inst),
@@ -2985,6 +2986,17 @@ fn airSplat(self: *Self, inst: Air.Inst.Index) InnerError!WValue {
     return self.fail("TODO: Implement wasm airSplat", .{});
 }
 
+fn airShuffle(self: *Self, inst: Air.Inst.Index) InnerError!WValue {
+    if (self.liveness.isUnused(inst)) return WValue{ .none = {} };
+
+    const ty_op = self.air.instructions.items(.data)[inst].ty_op;
+    const operand = try self.resolveInst(ty_op.operand);
+
+    _ = ty_op;
+    _ = operand;
+    return self.fail("TODO: Implement wasm airShuffle", .{});
+}
+
 fn airAggregateInit(self: *Self, inst: Air.Inst.Index) InnerError!WValue {
     if (self.liveness.isUnused(inst)) return WValue{ .none = {} };
 
diff --git a/src/arch/x86_64/CodeGen.zig b/src/arch/x86_64/CodeGen.zig
index 4adc59e662..68aa770ffc 100644
--- a/src/arch/x86_64/CodeGen.zig
+++ b/src/arch/x86_64/CodeGen.zig
@@ -720,6 +720,7 @@ fn genBody(self: *Self, body: []const Air.Inst.Index) InnerError!void {
             .tag_name        => try self.airTagName(inst),
             .error_name      => try self.airErrorName(inst),
             .splat           => try self.airSplat(inst),
+            .shuffle         => try self.airShuffle(inst),
             .aggregate_init  => try self.airAggregateInit(inst),
             .union_init      => try self.airUnionInit(inst),
             .prefetch        => try self.airPrefetch(inst),
@@ -5535,6 +5536,12 @@ fn airSplat(self: *Self, inst: Air.Inst.Index) !void {
     return self.finishAir(inst, result, .{ ty_op.operand, .none, .none });
 }
 
+fn airShuffle(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 airShuffle for x86_64", .{});
+    return self.finishAir(inst, result, .{ ty_op.operand, .none, .none });
+}
+
 fn airAggregateInit(self: *Self, inst: Air.Inst.Index) !void {
     const vector_ty = self.air.typeOfIndex(inst);
     const len = vector_ty.vectorLen();
diff --git a/src/codegen/c.zig b/src/codegen/c.zig
index 4a30bf023b..c179b65046 100644
--- a/src/codegen/c.zig
+++ b/src/codegen/c.zig
@@ -1716,6 +1716,7 @@ fn genBody(f: *Function, body: []const Air.Inst.Index) error{ AnalysisFail, OutO
             .tag_name         => try airTagName(f, inst),
             .error_name       => try airErrorName(f, inst),
             .splat            => try airSplat(f, inst),
+            .shuffle          => try airShuffle(f, inst),
             .aggregate_init   => try airAggregateInit(f, inst),
             .union_init       => try airUnionInit(f, inst),
             .prefetch         => try airPrefetch(f, inst),
@@ -3557,6 +3558,21 @@ fn airSplat(f: *Function, inst: Air.Inst.Index) !CValue {
     return f.fail("TODO: C backend: implement airSplat", .{});
 }
 
+fn airShuffle(f: *Function, inst: Air.Inst.Index) !CValue {
+    if (f.liveness.isUnused(inst)) return CValue.none;
+
+    const inst_ty = f.air.typeOfIndex(inst);
+    const ty_op = f.air.instructions.items(.data)[inst].ty_op;
+    const operand = try f.resolveInst(ty_op.operand);
+    const writer = f.object.writer();
+    const local = try f.allocLocal(inst_ty, .Const);
+    try writer.writeAll(" = ");
+
+    _ = operand;
+    _ = local;
+    return f.fail("TODO: C backend: implement airShuffle", .{});
+}
+
 fn airAggregateInit(f: *Function, inst: Air.Inst.Index) !CValue {
     if (f.liveness.isUnused(inst)) return CValue.none;
 
diff --git a/src/codegen/llvm.zig b/src/codegen/llvm.zig
index d7df161b00..190fcd0ee6 100644
--- a/src/codegen/llvm.zig
+++ b/src/codegen/llvm.zig
@@ -3204,6 +3204,7 @@ pub const FuncGen = struct {
                 .tag_name       => try self.airTagName(inst),
                 .error_name     => try self.airErrorName(inst),
                 .splat          => try self.airSplat(inst),
+                .shuffle        => try self.airShuffle(inst),
                 .aggregate_init => try self.airAggregateInit(inst),
                 .union_init     => try self.airUnionInit(inst),
                 .prefetch       => try self.airPrefetch(inst),
@@ -5850,6 +5851,43 @@ pub const FuncGen = struct {
         return self.builder.buildShuffleVector(op_vector, undef_vector, mask_llvm_ty.constNull(), "");
     }
 
+    fn airShuffle(self: *FuncGen, inst: Air.Inst.Index) !?*const llvm.Value {
+        if (self.liveness.isUnused(inst)) return null;
+
+        const ty_pl = self.air.instructions.items(.data)[inst].ty_pl;
+        const extra = self.air.extraData(Air.Shuffle, ty_pl.payload).data;
+        const a = try self.resolveInst(extra.a);
+        const b = try self.resolveInst(extra.b);
+        const mask = self.air.values[extra.mask];
+        const mask_len = extra.mask_len;
+        const a_len = self.air.typeOf(extra.a).vectorLen();
+
+        // LLVM uses integers larger than the length of the first array to
+        // index into the second array. This was deemed unnecessarily fragile
+        // when changing code, so Zig uses negative numbers to index the
+        // second vector. These start at -1 and go down, and are easiest to use
+        // with the ~ operator. Here we convert between the two formats.
+        const values = try self.gpa.alloc(*const llvm.Value, mask_len);
+        defer self.gpa.free(values);
+
+        const llvm_i32 = self.context.intType(32);
+
+        for (values) |*val, i| {
+            var buf: Value.ElemValueBuffer = undefined;
+            const elem = mask.elemValueBuffer(i, &buf);
+            if (elem.isUndef()) {
+                val.* = llvm_i32.getUndef();
+            } else {
+                const int = elem.toSignedInt();
+                const unsigned = if (int >= 0) @intCast(u32, int) else @intCast(u32, ~int + a_len);
+                val.* = llvm_i32.constInt(unsigned, .False);
+            }
+        }
+
+        const llvm_mask_value = llvm.constVector(values.ptr, mask_len);
+        return self.builder.buildShuffleVector(a, b, llvm_mask_value, "");
+    }
+
     fn airAggregateInit(self: *FuncGen, inst: Air.Inst.Index) !?*const llvm.Value {
         if (self.liveness.isUnused(inst)) return null;
 
diff --git a/src/print_air.zig b/src/print_air.zig
index 56d0cb9623..749e4751fb 100644
--- a/src/print_air.zig
+++ b/src/print_air.zig
@@ -258,6 +258,7 @@ const Writer = struct {
             .wasm_memory_size => try w.writeWasmMemorySize(s, inst),
             .wasm_memory_grow => try w.writeWasmMemoryGrow(s, inst),
             .mul_add => try w.writeMulAdd(s, inst),
+            .shuffle => try w.writeShuffle(s, inst),
 
             .add_with_overflow,
             .sub_with_overflow,
@@ -375,6 +376,16 @@ const Writer = struct {
         try w.writeOperand(s, inst, 2, pl_op.operand);
     }
 
+    fn writeShuffle(w: *Writer, s: anytype, inst: Air.Inst.Index) @TypeOf(s).Error!void {
+        const pl_op = w.air.instructions.items(.data)[inst].pl_op;
+        const extra = w.air.extraData(Air.Shuffle, pl_op.payload).data;
+
+        try w.writeOperand(s, inst, 0, extra.a);
+        try s.writeAll(", ");
+        try w.writeOperand(s, inst, 1, extra.b);
+        try s.print(", mask {d}, len {d}", .{ extra.mask, extra.mask_len });
+    }
+
     fn writeFence(w: *Writer, s: anytype, inst: Air.Inst.Index) @TypeOf(s).Error!void {
         const atomic_order = w.air.instructions.items(.data)[inst].fence;
 
diff --git a/src/value.zig b/src/value.zig
index 7c5401cd75..9117ef78df 100644
--- a/src/value.zig
+++ b/src/value.zig
@@ -1157,6 +1157,7 @@ pub const Value = extern union {
     ) Allocator.Error!Value {
         switch (ty.zigTypeTag()) {
             .Int => {
+                if (buffer.len == 0) return Value.zero;
                 const int_info = ty.intInfo(target);
                 const endian = target.cpu.arch.endian();
                 const Limb = std.math.big.Limb;
@@ -1819,7 +1820,22 @@ pub const Value = extern union {
     }
 
     /// Asserts the value is comparable.
+    /// For vectors this is only valid with op == .eq.
     pub fn compareWithZero(lhs: Value, op: std.math.CompareOperator) bool {
+        switch (lhs.tag()) {
+            .repeated => {
+                assert(op == .eq);
+                return lhs.castTag(.repeated).?.data.compareWithZero(.eq);
+            },
+            .array => {
+                assert(op == .eq);
+                for (lhs.cast(Payload.Array).?.data) |elem_val| {
+                    if (!elem_val.compareWithZero(.eq)) return false;
+                }
+                return true;
+            },
+            else => {},
+        }
         return orderAgainstZero(lhs).compare(op);
     }
 
@@ -2170,6 +2186,33 @@ pub const Value = extern union {
         };
     }
 
+    pub fn canMutateComptimeVarState(val: Value) bool {
+        if (val.isComptimeMutablePtr()) return true;
+        switch (val.tag()) {
+            .repeated => return val.castTag(.repeated).?.data.canMutateComptimeVarState(),
+            .array => {
+                const elems = val.cast(Payload.Array).?.data;
+                for (elems) |elem| {
+                    if (elem.canMutateComptimeVarState()) return true;
+                }
+                return false;
+            },
+            .eu_payload => return val.castTag(.eu_payload).?.data.canMutateComptimeVarState(),
+            .eu_payload_ptr => return val.castTag(.eu_payload_ptr).?.data.canMutateComptimeVarState(),
+            .opt_payload => return val.castTag(.opt_payload).?.data.canMutateComptimeVarState(),
+            .opt_payload_ptr => return val.castTag(.opt_payload_ptr).?.data.canMutateComptimeVarState(),
+            .@"struct" => {
+                const fields = val.cast(Payload.Struct).?.data;
+                for (fields) |field| {
+                    if (field.canMutateComptimeVarState()) return true;
+                }
+                return false;
+            },
+            .@"union" => return val.cast(Payload.Union).?.data.val.canMutateComptimeVarState(),
+            else => return false,
+        }
+    }
+
     /// Gets the decl referenced by this pointer.  If the pointer does not point
     /// to a decl, or if it points to some part of a decl (like field_ptr or element_ptr),
     /// this function returns null.