Merge pull request #8796 from Snektron/spirv

SPIR-V: Codegen basis

src/codegen/spirv.zig

@@ -1,44 +1,50 @@
 const std = @import("std");
 const Allocator = std.mem.Allocator;
+const Target = std.Target;
 const log = std.log.scoped(.codegen);
 
 const spec = @import("spirv/spec.zig");
+const Opcode = spec.Opcode;
+
 const Module = @import("../Module.zig");
 const Decl = Module.Decl;
 const Type = @import("../type.zig").Type;
+const Value = @import("../value.zig").Value;
+const LazySrcLoc = Module.LazySrcLoc;
+const ir = @import("../ir.zig");
+const Inst = ir.Inst;
 
 pub const TypeMap = std.HashMap(Type, u32, Type.hash, Type.eql, std.hash_map.default_max_load_percentage);
+pub const ValueMap = std.AutoHashMap(*Inst, u32);
 
-pub fn writeInstruction(code: *std.ArrayList(u32), instr: spec.Opcode, args: []const u32) !void {
-    const word_count = @intCast(u32, args.len + 1);
-    try code.append((word_count << 16) | @enumToInt(instr));
+pub fn writeOpcode(code: *std.ArrayList(u32), opcode: Opcode, arg_count: u32) !void {
+    const word_count = arg_count + 1;
+    try code.append((word_count << 16) | @enumToInt(opcode));
+}
+
+pub fn writeInstruction(code: *std.ArrayList(u32), opcode: Opcode, args: []const u32) !void {
+    try writeOpcode(code, opcode, @intCast(u32, args.len));
     try code.appendSlice(args);
 }
 
+/// This structure represents a SPIR-V binary module being compiled, and keeps track of relevant information
+/// such as code for the different logical sections, and the next result-id.
 pub const SPIRVModule = struct {
-    next_result_id: u32 = 0,
-
-    target: std.Target,
-
-    types: TypeMap,
-
-    types_and_globals: std.ArrayList(u32),
+    next_result_id: u32,
+    types_globals_constants: std.ArrayList(u32),
     fn_decls: std.ArrayList(u32),
 
-    pub fn init(target: std.Target, allocator: *Allocator) SPIRVModule {
+    pub fn init(allocator: *Allocator) SPIRVModule {
         return .{
-            .target = target,
-            .types = TypeMap.init(allocator),
-            .types_and_globals = std.ArrayList(u32).init(allocator),
+            .next_result_id = 1, // 0 is an invalid SPIR-V result ID.
+            .types_globals_constants = std.ArrayList(u32).init(allocator),
             .fn_decls = std.ArrayList(u32).init(allocator),
         };
     }
 
     pub fn deinit(self: *SPIRVModule) void {
+        self.types_globals_constants.deinit();
         self.fn_decls.deinit();
-        self.types_and_globals.deinit();
-        self.types.deinit();
-        self.* = undefined;
     }
 
     pub fn allocResultId(self: *SPIRVModule) u32 {
@@ -49,31 +55,326 @@ pub const SPIRVModule = struct {
     pub fn resultIdBound(self: *SPIRVModule) u32 {
         return self.next_result_id;
     }
+};
 
-    pub fn getOrGenType(self: *SPIRVModule, t: Type) !u32 {
+/// This structure is used to compile a declaration, and contains all relevant meta-information to deal with that.
+pub const DeclGen = struct {
+    module: *Module,
+    spv: *SPIRVModule,
+
+    args: std.ArrayList(u32),
+    next_arg_index: u32,
+
+    types: TypeMap,
+    values: ValueMap,
+
+    decl: *Decl,
+    error_msg: ?*Module.ErrorMsg,
+
+    const Error = error{
+        AnalysisFail,
+        OutOfMemory
+    };
+
+    /// This structure is used to return information about a type typically used for arithmetic operations.
+    /// These types may either be integers, floats, or a vector of these. Most scalar operations also work on vectors,
+    /// so we can easily represent those as arithmetic types.
+    /// If the type is a scalar, 'inner type' refers to the scalar type. Otherwise, if its a vector, it refers
+    /// to the vector's element type.
+    const ArithmeticTypeInfo = struct {
+        /// A classification of the inner type.
+        const Class = enum {
+            /// A boolean.
+            bool,
+
+            /// A regular, **native**, integer.
+            /// This is only returned when the backend supports this int as a native type (when
+            /// the relevant capability is enabled).
+            integer,
+
+            /// A regular float. These are all required to be natively supported. Floating points for
+            /// which the relevant capability is not enabled are not emulated.
+            float,
+
+            /// An integer of a 'strange' size (which' bit size is not the same as its backing type. **Note**: this
+            /// may **also** include power-of-2 integers for which the relevant capability is not enabled), but still
+            /// within the limits of the largest natively supported integer type.
+            strange_integer,
+
+            /// An integer with more bits than the largest natively supported integer type.
+            composite_integer,
+        };
+
+        /// The number of bits in the inner type.
+        /// Note: this is the actual number of bits of the type, not the size of the backing integer.
+        bits: u16,
+
+        /// Whether the type is a vector.
+        is_vector: bool,
+
+        /// Whether the inner type is signed. Only relevant for integers.
+        signedness: std.builtin.Signedness,
+
+        /// A classification of the inner type. These scenarios
+        /// will all have to be handled slightly different.
+        class: Class,
+    };
+
+    fn fail(self: *DeclGen, src: LazySrcLoc, comptime format: []const u8, args: anytype) Error {
+        @setCold(true);
+        const src_loc = src.toSrcLocWithDecl(self.decl);
+        self.error_msg = try Module.ErrorMsg.create(self.module.gpa, src_loc, format, args);
+        return error.AnalysisFail;
+    }
+
+    fn resolve(self: *DeclGen, inst: *Inst) !u32 {
+        if (inst.value()) |val| {
+            return self.genConstant(inst.ty, val);
+        }
+
+        return self.values.get(inst).?; // Instruction does not dominate all uses!
+    }
+
+    /// SPIR-V requires enabling specific integer sizes through capabilities, and so if they are not enabled, we need
+    /// to emulate them in other instructions/types. This function returns, given an integer bit width (signed or unsigned, sign
+    /// included), the width of the underlying type which represents it, given the enabled features for the current target.
+    /// If the result is `null`, the largest type the target platform supports natively is not able to perform computations using
+    /// that size. In this case, multiple elements of the largest type should be used.
+    /// The backing type will be chosen as the smallest supported integer larger or equal to it in number of bits.
+    /// The result is valid to be used with OpTypeInt.
+    /// TODO: The extension SPV_INTEL_arbitrary_precision_integers allows any integer size (at least up to 32 bits).
+    /// TODO: This probably needs an ABI-version as well (especially in combination with SPV_INTEL_arbitrary_precision_integers).
+    /// TODO: Should the result of this function be cached?
+    fn backingIntBits(self: *DeclGen, bits: u16) ?u16 {
+        const target = self.module.getTarget();
+
+        // TODO: Figure out what to do with u0/i0.
+        std.debug.assert(bits != 0);
+
+        // 8, 16 and 64-bit integers require the Int8, Int16 and Inr64 capabilities respectively.
+        // 32-bit integers are always supported (see spec, 2.16.1, Data rules).
+        const ints = [_]struct{ bits: u16, feature: ?Target.spirv.Feature } {
+            .{ .bits = 8, .feature = .Int8 },
+            .{ .bits = 16, .feature = .Int16 },
+            .{ .bits = 32, .feature = null },
+            .{ .bits = 64, .feature = .Int64 },
+        };
+
+        for (ints) |int| {
+            const has_feature = if (int.feature) |feature|
+                Target.spirv.featureSetHas(target.cpu.features, feature)
+            else
+                true;
+
+            if (bits <= int.bits and has_feature) {
+                return int.bits;
+            }
+        }
+
+        return null;
+    }
+
+    /// Return the amount of bits in the largest supported integer type. This is either 32 (always supported), or 64 (if
+    /// the Int64 capability is enabled).
+    /// Note: The extension SPV_INTEL_arbitrary_precision_integers allows any integer size (at least up to 32 bits).
+    /// In theory that could also be used, but since the spec says that it only guarantees support up to 32-bit ints there
+    /// is no way of knowing whether those are actually supported.
+    /// TODO: Maybe this should be cached?
+    fn largestSupportedIntBits(self: *DeclGen) u16 {
+        const target = self.module.getTarget();
+        return if (Target.spirv.featureSetHas(target.cpu.features, .Int64))
+            64
+        else
+            32;
+    }
+
+    /// Checks whether the type is "composite int", an integer consisting of multiple native integers. These are represented by
+    /// arrays of largestSupportedIntBits().
+    /// Asserts `ty` is an integer.
+    fn isCompositeInt(self: *DeclGen, ty: Type) bool {
+        return self.backingIntBits(ty) == null;
+    }
+
+    fn arithmeticTypeInfo(self: *DeclGen, ty: Type) !ArithmeticTypeInfo {
+        const target = self.module.getTarget();
+
+        return switch (ty.zigTypeTag()) {
+            .Bool => ArithmeticTypeInfo{
+                .bits = 1, // Doesn't matter for this class.
+                .is_vector = false,
+                .signedness = .unsigned, // Technically, but doesn't matter for this class.
+                .class = .bool,
+            },
+            .Float => ArithmeticTypeInfo{
+                .bits = ty.floatBits(target),
+                .is_vector = false,
+                .signedness = .signed, // Technically, but doesn't matter for this class.
+                .class = .float,
+            },
+            .Int => blk: {
+                const int_info = ty.intInfo(target);
+                // TODO: Maybe it's useful to also return this value.
+                const maybe_backing_bits = self.backingIntBits(int_info.bits);
+                break :blk ArithmeticTypeInfo{
+                    .bits = int_info.bits,
+                    .is_vector = false,
+                    .signedness = int_info.signedness,
+                    .class = if (maybe_backing_bits) |backing_bits|
+                            if (backing_bits == int_info.bits)
+                                ArithmeticTypeInfo.Class.integer
+                            else
+                                ArithmeticTypeInfo.Class.strange_integer
+                        else
+                            .composite_integer
+                };
+            },
+            // As of yet, there is no vector support in the self-hosted compiler.
+            .Vector => self.fail(.{.node_offset = 0}, "TODO: SPIR-V backend: implement arithmeticTypeInfo for Vector", .{}),
+            // TODO: For which types is this the case?
+            else => self.fail(.{.node_offset = 0}, "TODO: SPIR-V backend: implement arithmeticTypeInfo for {}", .{ty}),
+        };
+    }
+
+    /// Generate a constant representing `val`.
+    /// TODO: Deduplication?
+    fn genConstant(self: *DeclGen, ty: Type, val: Value) Error!u32 {
+        const code = &self.spv.types_globals_constants;
+        const result_id = self.spv.allocResultId();
+        const result_type_id = try self.getOrGenType(ty);
+
+        if (val.isUndef()) {
+            try writeInstruction(code, .OpUndef, &[_]u32{ result_type_id, result_id });
+            return result_id;
+        }
+
+        switch (ty.zigTypeTag()) {
+            .Bool => {
+                const opcode: Opcode = if (val.toBool()) .OpConstantTrue else .OpConstantFalse;
+                try writeInstruction(code, opcode, &[_]u32{ result_type_id, result_id });
+            },
+            .Float => {
+                // At this point we are guaranteed that the target floating point type is supported, otherwise the function
+                // would have exited at getOrGenType(ty).
+
+                // f16 and f32 require one word of storage. f64 requires 2, low-order first.
+
+                switch (val.tag()) {
+                    .float_16 => try writeInstruction(code, .OpConstant, &[_]u32{
+                        result_type_id,
+                        result_id,
+                        @bitCast(u16, val.castTag(.float_16).?.data)
+                    }),
+                    .float_32 => try writeInstruction(code, .OpConstant, &[_]u32{
+                        result_type_id,
+                        result_id,
+                        @bitCast(u32, val.castTag(.float_32).?.data)
+                    }),
+                    .float_64 => {
+                        const float_bits = @bitCast(u64, val.castTag(.float_64).?.data);
+                        try writeInstruction(code, .OpConstant, &[_]u32{
+                            result_type_id,
+                            result_id,
+                            @truncate(u32, float_bits),
+                            @truncate(u32, float_bits >> 32),
+                        });
+                    },
+                    .float_128 => unreachable, // Filtered out in the call to getOrGenType.
+                    // TODO: What tags do we need to handle here anyway?
+                    else => return self.fail(.{.node_offset = 0}, "TODO: SPIR-V backend: float constant generation of value {s}\n", .{ val.tag() }),
+                }
+            },
+            else => return self.fail(.{.node_offset = 0}, "TODO: SPIR-V backend: constant generation of type {s}\n", .{ ty.zigTypeTag() }),
+        }
+
+        return result_id;
+    }
+
+    fn getOrGenType(self: *DeclGen, ty: Type) Error!u32 {
         // We can't use getOrPut here so we can recursively generate types.
-        if (self.types.get(t)) |already_generated| {
+        if (self.types.get(ty)) |already_generated| {
             return already_generated;
         }
 
-        const result = self.allocResultId();
+        const target = self.module.getTarget();
+        const code = &self.spv.types_globals_constants;
+        const result_id = self.spv.allocResultId();
 
-        switch (t.zigTypeTag()) {
-            .Void => try writeInstruction(&self.types_and_globals, .OpTypeVoid, &[_]u32{ result }),
-            .Bool => try writeInstruction(&self.types_and_globals, .OpTypeBool, &[_]u32{ result }),
+        switch (ty.zigTypeTag()) {
+            .Void => try writeInstruction(code, .OpTypeVoid, &[_]u32{ result_id }),
+            .Bool => try writeInstruction(code, .OpTypeBool, &[_]u32{ result_id }),
             .Int => {
-                const int_info = t.intInfo(self.target);
-                try writeInstruction(&self.types_and_globals, .OpTypeInt, &[_]u32{
-                    result,
-                    int_info.bits,
+                const int_info = ty.intInfo(target);
+                const backing_bits = self.backingIntBits(int_info.bits) orelse {
+                    // Integers too big for any native type are represented as "composite integers": An array of largestSupportedIntBits.
+                    return self.fail(.{.node_offset = 0}, "TODO: SPIR-V backend: implement composite ints {}", .{ ty });
+                };
+
+                // TODO: If backing_bits != int_info.bits, a duplicate type might be generated here.
+                try writeInstruction(code, .OpTypeInt, &[_]u32{
+                    result_id,
+                    backing_bits,
                     switch (int_info.signedness) {
                         .unsigned => 0,
                         .signed => 1,
                     },
                 });
             },
-            // TODO: Verify that floatBits() will be correct.
-            .Float => try writeInstruction(&self.types_and_globals, .OpTypeFloat, &[_]u32{ result, t.floatBits(self.target) }),
+            .Float => {
+                // We can (and want) not really emulate floating points with other floating point types like with the integer types,
+                // so if the float is not supported, just return an error.
+                const bits = ty.floatBits(target);
+                const supported = switch (bits) {
+                    16 => Target.spirv.featureSetHas(target.cpu.features, .Float16),
+                    // 32-bit floats are always supported (see spec, 2.16.1, Data rules).
+                    32 => true,
+                    64 => Target.spirv.featureSetHas(target.cpu.features, .Float64),
+                    else => false,
+                };
+
+                if (!supported) {
+                    return self.fail(.{.node_offset = 0}, "Floating point width of {} bits is not supported for the current SPIR-V feature set", .{ bits });
+                }
+
+                try writeInstruction(code, .OpTypeFloat, &[_]u32{ result_id, bits });
+            },
+            .Fn => {
+                // We only support zig-calling-convention functions, no varargs.
+                if (ty.fnCallingConvention() != .Unspecified)
+                    return self.fail(.{.node_offset = 0}, "Unsupported calling convention for SPIR-V", .{});
+                if (ty.fnIsVarArgs())
+                    return self.fail(.{.node_offset = 0}, "VarArgs unsupported for SPIR-V", .{});
+
+                // In order to avoid a temporary here, first generate all the required types and then simply look them up
+                // when generating the function type.
+                const params = ty.fnParamLen();
+                var i: usize = 0;
+                while (i < params) : (i += 1) {
+                    _ = try self.getOrGenType(ty.fnParamType(i));
+                }
+
+                const return_type_id = try self.getOrGenType(ty.fnReturnType());
+
+                // result id + result type id + parameter type ids.
+                try writeOpcode(code, .OpTypeFunction, 2 + @intCast(u32, ty.fnParamLen()) );
+                try code.appendSlice(&.{ result_id, return_type_id });
+
+                i = 0;
+                while (i < params) : (i += 1) {
+                    const param_type_id = self.types.get(ty.fnParamType(i)).?;
+                    try code.append(param_type_id);
+                }
+            },
+            .Vector => {
+                // Although not 100% the same, Zig vectors map quite neatly to SPIR-V vectors (including many integer and float operations
+                // which work on them), so simply use those.
+                // Note: SPIR-V vectors only support bools, ints and floats, so pointer vectors need to be supported another way.
+                // "composite integers" (larger than the largest supported native type) can probably be represented by an array of vectors.
+                // TODO: The SPIR-V spec mentions that vector sizes may be quite restricted! look into which we can use, and whether OpTypeVector
+                // is adequate at all for this.
+
+                // TODO: Vectors are not yet supported by the self-hosted compiler itself it seems.
+                return self.fail(.{.node_offset = 0}, "TODO: SPIR-V backend: implement type Vector", .{});
+            },
             .Null,
             .Undefined,
             .EnumLiteral,
@@ -84,23 +385,197 @@ pub const SPIRVModule = struct {
 
             .BoundFn => unreachable, // this type will be deleted from the language.
 
-            else => return error.TODO,
+            else => |tag| return self.fail(.{.node_offset = 0}, "TODO: SPIR-V backend: implement type {}s", .{ tag }),
         }
 
-        try self.types.put(t, result);
-        return result;
+        try self.types.putNoClobber(ty, result_id);
+        return result_id;
     }
 
-    pub fn gen(self: *SPIRVModule, decl: *Decl) !void {
-        const typed_value = decl.typed_value.most_recent.typed_value;
+    pub fn gen(self: *DeclGen) !void {
+        const result_id = self.decl.fn_link.spirv.id;
+        const tv = self.decl.typed_value.most_recent.typed_value;
 
-        switch (typed_value.ty.zigTypeTag()) {
-            .Fn => {
-                log.debug("Generating code for function '{s}'", .{ std.mem.spanZ(decl.name) });
+        if (tv.val.castTag(.function)) |func_payload| {
+            std.debug.assert(tv.ty.zigTypeTag() == .Fn);
+            const prototype_id = try self.getOrGenType(tv.ty);
+            try writeInstruction(&self.spv.fn_decls, .OpFunction, &[_]u32{
+                self.types.get(tv.ty.fnReturnType()).?, // This type should be generated along with the prototype.
+                result_id,
+                @bitCast(u32, spec.FunctionControl{}), // TODO: We can set inline here if the type requires it.
+                prototype_id,
+            });
 
-                _ = try self.getOrGenType(typed_value.ty.fnReturnType());
-            },
-            else => return error.TODO,
+            const params = tv.ty.fnParamLen();
+            var i: usize = 0;
+
+            try self.args.ensureCapacity(params);
+            while (i < params) : (i += 1) {
+                const param_type_id = self.types.get(tv.ty.fnParamType(i)).?;
+                const arg_result_id = self.spv.allocResultId();
+                try writeInstruction(&self.spv.fn_decls, .OpFunctionParameter, &[_]u32{ param_type_id, arg_result_id });
+                self.args.appendAssumeCapacity(arg_result_id);
+            }
+
+            // TODO: This could probably be done in a better way...
+            const root_block_id = self.spv.allocResultId();
+            _ = try writeInstruction(&self.spv.fn_decls, .OpLabel, &[_]u32{root_block_id});
+            try self.genBody(func_payload.data.body);
+
+            try writeInstruction(&self.spv.fn_decls, .OpFunctionEnd, &[_]u32{});
+        } else {
+            return self.fail(.{.node_offset = 0}, "TODO: SPIR-V backend: generate decl type {}", .{ tv.ty.zigTypeTag() });
         }
     }
+
+    fn genBody(self: *DeclGen, body: ir.Body) !void {
+        for (body.instructions) |inst| {
+            const maybe_result_id = try self.genInst(inst);
+            if (maybe_result_id) |result_id|
+                try self.values.putNoClobber(inst, result_id);
+        }
+    }
+
+    fn genInst(self: *DeclGen, inst: *Inst) !?u32 {
+        return switch (inst.tag) {
+            .add, .addwrap => try self.genBinOp(inst.castTag(.add).?),
+            .sub, .subwrap => try self.genBinOp(inst.castTag(.sub).?),
+            .mul, .mulwrap => try self.genBinOp(inst.castTag(.mul).?),
+            .div => try self.genBinOp(inst.castTag(.div).?),
+            .bit_and => try self.genBinOp(inst.castTag(.bit_and).?),
+            .bit_or => try self.genBinOp(inst.castTag(.bit_or).?),
+            .xor => try self.genBinOp(inst.castTag(.xor).?),
+            .cmp_eq => try self.genBinOp(inst.castTag(.cmp_eq).?),
+            .cmp_neq => try self.genBinOp(inst.castTag(.cmp_neq).?),
+            .cmp_gt => try self.genBinOp(inst.castTag(.cmp_gt).?),
+            .cmp_gte => try self.genBinOp(inst.castTag(.cmp_gte).?),
+            .cmp_lt => try self.genBinOp(inst.castTag(.cmp_lt).?),
+            .cmp_lte => try self.genBinOp(inst.castTag(.cmp_lte).?),
+            .bool_and => try self.genBinOp(inst.castTag(.bool_and).?),
+            .bool_or => try self.genBinOp(inst.castTag(.bool_or).?),
+            .not => try self.genUnOp(inst.castTag(.not).?),
+            .arg => self.genArg(),
+            // TODO: Breakpoints won't be supported in SPIR-V, but the compiler seems to insert them
+            // throughout the IR.
+            .breakpoint => null,
+            .dbg_stmt => null,
+            .ret => self.genRet(inst.castTag(.ret).?),
+            .retvoid => self.genRetVoid(),
+            .unreach => self.genUnreach(),
+            else => self.fail(.{.node_offset = 0}, "TODO: SPIR-V backend: implement inst {}", .{inst.tag}),
+        };
+    }
+
+    fn genBinOp(self: *DeclGen, inst: *Inst.BinOp) !u32 {
+        // TODO: Will lhs and rhs have the same type?
+        const lhs_id = try self.resolve(inst.lhs);
+        const rhs_id = try self.resolve(inst.rhs);
+
+        const result_id = self.spv.allocResultId();
+        const result_type_id = try self.getOrGenType(inst.base.ty);
+
+        // TODO: Is the result the same as the argument types?
+        // This is supposed to be the case for SPIR-V.
+        std.debug.assert(inst.rhs.ty.eql(inst.lhs.ty));
+        std.debug.assert(inst.base.ty.tag() == .bool or inst.base.ty.eql(inst.lhs.ty));
+
+        // Binary operations are generally applicable to both scalar and vector operations in SPIR-V, but int and float
+        // versions of operations require different opcodes.
+        // For operations which produce bools, the information of inst.base.ty is not useful, so just pick either operand
+        // instead.
+        const info = try self.arithmeticTypeInfo(inst.lhs.ty);
+
+        if (info.class == .composite_integer)
+            return self.fail(.{.node_offset = 0}, "TODO: SPIR-V backend: binary operations for composite integers", .{});
+
+        const is_bool = info.class == .bool;
+        const is_float = info.class == .float;
+        const is_signed = info.signedness == .signed;
+        // **Note**: All these operations must be valid for vectors of floats, integers and bools as well!
+        // For floating points, we generally want ordered operations (which return false if either operand is nan).
+        const opcode = switch (inst.base.tag) {
+            // The regular integer operations are all defined for wrapping. Since theyre only relevant for integers,
+            // we can just switch on both cases here.
+            .add, .addwrap => if (is_float) Opcode.OpFAdd else Opcode.OpIAdd,
+            .sub, .subwrap => if (is_float) Opcode.OpFSub else Opcode.OpISub,
+            .mul, .mulwrap => if (is_float) Opcode.OpFMul else Opcode.OpIMul,
+            // TODO: Trap if divisor is 0?
+            // TODO: Figure out of OpSDiv for unsigned/OpUDiv for signed does anything useful.
+            //  => Those are probably for divTrunc and divFloor, though the compiler does not yet generate those.
+            //  => TODO: Figure out how those work on the SPIR-V side.
+            //  => TODO: Test these.
+            .div => if (is_float) Opcode.OpFDiv else if (is_signed) Opcode.OpSDiv else Opcode.OpUDiv,
+            // Only integer versions for these.
+            .bit_and => Opcode.OpBitwiseAnd,
+            .bit_or => Opcode.OpBitwiseOr,
+            .xor => Opcode.OpBitwiseXor,
+            // Int/bool/float -> bool operations.
+            .cmp_eq => if (is_float) Opcode.OpFOrdEqual else if (is_bool) Opcode.OpLogicalEqual else Opcode.OpIEqual,
+            .cmp_neq => if (is_float) Opcode.OpFOrdNotEqual else if (is_bool) Opcode.OpLogicalNotEqual else Opcode.OpINotEqual,
+            // Int/float -> bool operations.
+            // TODO: Verify that these OpFOrd type operations produce the right value.
+            // TODO: Is there a more fundamental difference between OpU and OpS operations here than just the type?
+            .cmp_gt => if (is_float) Opcode.OpFOrdGreaterThan else if (is_signed) Opcode.OpSGreaterThan else Opcode.OpUGreaterThan,
+            .cmp_gte => if (is_float) Opcode.OpFOrdGreaterThanEqual else if (is_signed) Opcode.OpSGreaterThanEqual else Opcode.OpUGreaterThanEqual,
+            .cmp_lt => if (is_float) Opcode.OpFOrdLessThan else if (is_signed) Opcode.OpSLessThan else Opcode.OpULessThan,
+            .cmp_lte => if (is_float) Opcode.OpFOrdLessThanEqual else if (is_signed) Opcode.OpSLessThanEqual else Opcode.OpULessThanEqual,
+            // Bool -> bool operations.
+            .bool_and => Opcode.OpLogicalAnd,
+            .bool_or => Opcode.OpLogicalOr,
+            else => unreachable,
+        };
+
+        try writeInstruction(&self.spv.fn_decls, opcode, &[_]u32{ result_type_id, result_id, lhs_id, rhs_id });
+
+        // TODO: Trap on overflow? Probably going to be annoying.
+        // TODO: Look into SPV_KHR_no_integer_wrap_decoration which provides NoSignedWrap/NoUnsignedWrap.
+
+        if (info.class != .strange_integer)
+            return result_id;
+
+        return self.fail(.{.node_offset = 0}, "TODO: SPIR-V backend: strange integer operation mask", .{});
+    }
+
+    fn genUnOp(self: *DeclGen, inst: *Inst.UnOp) !u32 {
+        const operand_id = try self.resolve(inst.operand);
+
+        const result_id = self.spv.allocResultId();
+        const result_type_id = try self.getOrGenType(inst.base.ty);
+
+        const info = try self.arithmeticTypeInfo(inst.operand.ty);
+
+        const opcode = switch (inst.base.tag) {
+            // Bool -> bool
+            .not => Opcode.OpLogicalNot,
+            else => unreachable,
+        };
+
+        try writeInstruction(&self.spv.fn_decls, opcode, &[_]u32{ result_type_id, result_id, operand_id });
+
+        return result_id;
+    }
+
+    fn genArg(self: *DeclGen) u32 {
+        defer self.next_arg_index += 1;
+        return self.args.items[self.next_arg_index];
+    }
+
+    fn genRet(self: *DeclGen, inst: *Inst.UnOp) !?u32 {
+        const operand_id = try self.resolve(inst.operand);
+        // TODO: This instruction needs to be the last in a block. Is that guaranteed?
+        try writeInstruction(&self.spv.fn_decls, .OpReturnValue, &[_]u32{ operand_id });
+        return null;
+    }
+
+    fn genRetVoid(self: *DeclGen) !?u32 {
+        // TODO: This instruction needs to be the last in a block. Is that guaranteed?
+        try writeInstruction(&self.spv.fn_decls, .OpReturn, &[_]u32{});
+        return null;
+    }
+
+    fn genUnreach(self: *DeclGen) !?u32 {
+        // TODO: This instruction needs to be the last in a block. Is that guaranteed?
+        try writeInstruction(&self.spv.fn_decls, .OpUnreachable, &[_]u32{});
+        return null;
+    }
 };

src/link/SpirV.zig

@@ -118,8 +118,8 @@ pub fn flushModule(self: *SpirV, comp: *Compilation) !void {
     const module = self.base.options.module.?;
     const target = comp.getTarget();
 
-    var spirv_module = codegen.SPIRVModule.init(target, self.base.allocator);
-    defer spirv_module.deinit();
+    var spv = codegen.SPIRVModule.init(self.base.allocator);
+    defer spv.deinit();
 
     // Allocate an ID for every declaration before generating code,
     // so that we can access them before processing them.
@@ -132,19 +132,48 @@ pub fn flushModule(self: *SpirV, comp: *Compilation) !void {
             if (decl.typed_value != .most_recent)
                 continue;
 
-            decl.fn_link.spirv.id = spirv_module.allocResultId();
+            decl.fn_link.spirv.id = spv.allocResultId();
             log.debug("Allocating id {} to '{s}'", .{ decl.fn_link.spirv.id, std.mem.spanZ(decl.name) });
         }
     }
 
     // Now, actually generate the code for all declarations.
     {
+        // We are just going to re-use this same DeclGen for every Decl, and we are just going to
+        // change the decl. Otherwise, we would have to keep a separate `args` and `types`, and re-construct this
+        // structure every time.
+        var decl_gen = codegen.DeclGen{
+            .module = module,
+            .spv = &spv,
+            .args = std.ArrayList(u32).init(self.base.allocator),
+            .next_arg_index = undefined,
+            .types = codegen.TypeMap.init(self.base.allocator),
+            .values = codegen.ValueMap.init(self.base.allocator),
+            .decl = undefined,
+            .error_msg = undefined,
+        };
+
+        defer decl_gen.values.deinit();
+        defer decl_gen.types.deinit();
+        defer decl_gen.args.deinit();
+
         for (module.decl_table.items()) |entry| {
             const decl = entry.value;
             if (decl.typed_value != .most_recent)
                 continue;
 
-            try spirv_module.gen(decl);
+            decl_gen.args.items.len = 0;
+            decl_gen.next_arg_index = 0;
+            decl_gen.decl = decl;
+            decl_gen.error_msg = null;
+
+            decl_gen.gen() catch |err| switch (err) {
+                error.AnalysisFail => {
+                    try module.failed_decls.put(module.gpa, decl, decl_gen.error_msg.?);
+                    return;
+                },
+                else => |e| return e,
+            };
         }
     }
 
@@ -155,7 +184,7 @@ pub fn flushModule(self: *SpirV, comp: *Compilation) !void {
         spec.magic_number,
         (spec.version.major << 16) | (spec.version.minor << 8),
         0, // TODO: Register Zig compiler magic number.
-        spirv_module.resultIdBound(), // ID bound.
+        spv.resultIdBound(), // ID bound.
         0, // Schema (currently reserved for future use in the SPIR-V spec).
     });
 
@@ -166,8 +195,8 @@ pub fn flushModule(self: *SpirV, comp: *Compilation) !void {
     // follows the SPIR-V logical module format!
     var all_buffers = [_]std.os.iovec_const{
         wordsToIovConst(binary.items),
-        wordsToIovConst(spirv_module.types_and_globals.items),
-        wordsToIovConst(spirv_module.fn_decls.items),
+        wordsToIovConst(spv.types_globals_constants.items),
+        wordsToIovConst(spv.fn_decls.items),
     };
 
     const file = self.base.file.?;