Merge pull request #12918 from jacobly0/math-cast-comptime-int

std.math: fix behavior relating to comptime_int arguments

build.zig

@@ -554,6 +554,8 @@ fn addCmakeCfgOptionsToExe(
     }) catch unreachable);
     assert(cfg.lld_include_dir.len != 0);
     exe.addIncludePath(cfg.lld_include_dir);
+    exe.addIncludePath(cfg.llvm_include_dir);
+    exe.addLibraryPath(cfg.llvm_lib_dir);
     addCMakeLibraryList(exe, cfg.clang_libraries);
     addCMakeLibraryList(exe, cfg.lld_libraries);
     addCMakeLibraryList(exe, cfg.llvm_libraries);
@@ -684,6 +686,8 @@ const CMakeConfig = struct {
     lld_include_dir: []const u8,
     lld_libraries: []const u8,
     clang_libraries: []const u8,
+    llvm_lib_dir: []const u8,
+    llvm_include_dir: []const u8,
     llvm_libraries: []const u8,
     dia_guids_lib: []const u8,
 };
@@ -745,6 +749,8 @@ fn parseConfigH(b: *Builder, config_h_text: []const u8) ?CMakeConfig {
         .lld_include_dir = undefined,
         .lld_libraries = undefined,
         .clang_libraries = undefined,
+        .llvm_lib_dir = undefined,
+        .llvm_include_dir = undefined,
         .llvm_libraries = undefined,
         .dia_guids_lib = undefined,
     };
@@ -782,6 +788,14 @@ fn parseConfigH(b: *Builder, config_h_text: []const u8) ?CMakeConfig {
             .prefix = "#define ZIG_DIA_GUIDS_LIB ",
             .field = "dia_guids_lib",
         },
+        .{
+            .prefix = "#define ZIG_LLVM_INCLUDE_PATH ",
+            .field = "llvm_include_dir",
+        },
+        .{
+            .prefix = "#define ZIG_LLVM_LIB_PATH ",
+            .field = "llvm_lib_dir",
+        },
         // .prefix = ZIG_LLVM_LINK_MODE parsed manually below
     };
 

lib/std/math.zig

@@ -1063,10 +1063,11 @@ test "negateCast" {
 /// return null.
 pub fn cast(comptime T: type, x: anytype) ?T {
     comptime assert(@typeInfo(T) == .Int); // must pass an integer
-    comptime assert(@typeInfo(@TypeOf(x)) == .Int); // must pass an integer
-    if (maxInt(@TypeOf(x)) > maxInt(T) and x > maxInt(T)) {
+    const is_comptime = @TypeOf(x) == comptime_int;
+    comptime assert(is_comptime or @typeInfo(@TypeOf(x)) == .Int); // must pass an integer
+    if ((is_comptime or maxInt(@TypeOf(x)) > maxInt(T)) and x > maxInt(T)) {
         return null;
-    } else if (minInt(@TypeOf(x)) < minInt(T) and x < minInt(T)) {
+    } else if ((is_comptime or minInt(@TypeOf(x)) < minInt(T)) and x < minInt(T)) {
         return null;
     } else {
         return @intCast(T, x);
@@ -1074,12 +1075,18 @@ pub fn cast(comptime T: type, x: anytype) ?T {
 }
 
 test "cast" {
+    try testing.expect(cast(u8, 300) == null);
     try testing.expect(cast(u8, @as(u32, 300)) == null);
+    try testing.expect(cast(i8, -200) == null);
     try testing.expect(cast(i8, @as(i32, -200)) == null);
+    try testing.expect(cast(u8, -1) == null);
     try testing.expect(cast(u8, @as(i8, -1)) == null);
+    try testing.expect(cast(u64, -1) == null);
     try testing.expect(cast(u64, @as(i8, -1)) == null);
 
+    try testing.expect(cast(u8, 255).? == @as(u8, 255));
     try testing.expect(cast(u8, @as(u32, 255)).? == @as(u8, 255));
+    try testing.expect(@TypeOf(cast(u8, 255).?) == u8);
     try testing.expect(@TypeOf(cast(u8, @as(u32, 255)).?) == u8);
 }
 

lib/std/math/big/int.zig

@@ -21,6 +21,9 @@ const debug_safety = false;
 
 /// Returns the number of limbs needed to store `scalar`, which must be a
 /// primitive integer value.
+/// Note: A comptime-known upper bound of this value that may be used
+/// instead if `scalar` is not already comptime-known is
+/// `calcTwosCompLimbCount(@typeInfo(@TypeOf(scalar)).Int.bits)`
 pub fn calcLimbLen(scalar: anytype) usize {
     if (scalar == 0) {
         return 1;
@@ -391,7 +394,18 @@ pub const Mutable = struct {
     /// Asserts the result fits in `r`. An upper bound on the number of limbs needed by
     /// r is `math.max(a.limbs.len, calcLimbLen(scalar)) + 1`.
     pub fn addScalar(r: *Mutable, a: Const, scalar: anytype) void {
-        var limbs: [calcLimbLen(scalar)]Limb = undefined;
+        // Normally we could just determine the number of limbs needed with calcLimbLen,
+        // but that is not comptime-known when scalar is not a comptime_int.  Instead, we
+        // use calcTwosCompLimbCount for a non-comptime_int scalar, which can be pessimistic
+        // in the case that scalar happens to be small in magnitude within its type, but it
+        // is well worth being able to use the stack and not needing an allocator passed in.
+        // Note that Mutable.init still sets len to calcLimbLen(scalar) in any case.
+        const limb_len = comptime switch (@typeInfo(@TypeOf(scalar))) {
+            .ComptimeInt => calcLimbLen(scalar),
+            .Int => |info| calcTwosCompLimbCount(info.bits),
+            else => @compileError("expected scalar to be an int"),
+        };
+        var limbs: [limb_len]Limb = undefined;
         const operand = init(&limbs, scalar).toConst();
         return add(r, a, operand);
     }
@@ -2303,7 +2317,18 @@ pub const Const = struct {
 
     /// Same as `order` but the right-hand operand is a primitive integer.
     pub fn orderAgainstScalar(lhs: Const, scalar: anytype) math.Order {
-        var limbs: [calcLimbLen(scalar)]Limb = undefined;
+        // Normally we could just determine the number of limbs needed with calcLimbLen,
+        // but that is not comptime-known when scalar is not a comptime_int.  Instead, we
+        // use calcTwosCompLimbCount for a non-comptime_int scalar, which can be pessimistic
+        // in the case that scalar happens to be small in magnitude within its type, but it
+        // is well worth being able to use the stack and not needing an allocator passed in.
+        // Note that Mutable.init still sets len to calcLimbLen(scalar) in any case.
+        const limb_len = comptime switch (@typeInfo(@TypeOf(scalar))) {
+            .ComptimeInt => calcLimbLen(scalar),
+            .Int => |info| calcTwosCompLimbCount(info.bits),
+            else => @compileError("expected scalar to be an int"),
+        };
+        var limbs: [limb_len]Limb = undefined;
         const rhs = Mutable.init(&limbs, scalar);
         return order(lhs, rhs.toConst());
     }

lib/std/math/big/int_test.zig

@@ -573,7 +573,7 @@ test "big.int add sign" {
     try testing.expect((try a.to(i32)) == -3);
 }
 
-test "big.int add scalar" {
+test "big.int add comptime scalar" {
     var a = try Managed.initSet(testing.allocator, 50);
     defer a.deinit();
 
@@ -584,6 +584,17 @@ test "big.int add scalar" {
     try testing.expect((try b.to(u32)) == 55);
 }
 
+test "big.int add scalar" {
+    var a = try Managed.initSet(testing.allocator, 123);
+    defer a.deinit();
+
+    var b = try Managed.init(testing.allocator);
+    defer b.deinit();
+    try b.addScalar(&a, @as(u32, 31));
+
+    try testing.expect((try b.to(u32)) == 154);
+}
+
 test "big.int addWrap single-single, unsigned" {
     var a = try Managed.initSet(testing.allocator, maxInt(u17));
     defer a.deinit();

src/stage1/config.h.in

@@ -22,6 +22,8 @@
 #define ZIG_LLD_INCLUDE_PATH "@LLD_INCLUDE_DIRS@"
 #define ZIG_LLD_LIBRARIES "@LLD_LIBRARIES@"
 #define ZIG_CLANG_LIBRARIES "@CLANG_LIBRARIES@"
+#define ZIG_LLVM_INCLUDE_PATH "@LLVM_INCLUDE_DIRS@"
+#define ZIG_LLVM_LIB_PATH "@LLVM_LIBDIRS@"
 #define ZIG_LLVM_LIBRARIES "@LLVM_LIBRARIES@"
 #define ZIG_DIA_GUIDS_LIB "@ZIG_DIA_GUIDS_LIB_ESCAPED@"