[DSLX:TS] Fixes ability to use xN based types as bit slices, use for std::{min,max}

docs_src/tutorials/intro_to_parametrics.md

@@ -2,7 +2,8 @@
 
 This tutorial demonstrates how types and functions can be parameterized to
 enable them to work on data of different formats and layouts, e.g., for a
-function `foo` to work on both u16 and u32 data types, and anywhere in between.
+function `foo` to work on both `u16` and `u32` data types, and anywhere in
+between.
 
 It's recommended that you're familiar with the concepts in the previous
 tutorial,
@@ -11,7 +12,7 @@ before following this tutorial.
 
 ## Simple parametrics
 
-Consider the simple example of the `umax` function
+Consider the simple example of a `umax` function -- similar to the `max` function
 [in the DSLX standard library](https://github.com/google/xls/tree/main/xls/dslx/stdlib/std.x):
 
 ```dslx
@@ -40,10 +41,12 @@ infer them:
 Explicit specification:
 
 ```dslx
-import std;
+fn umax<N: u32>(x: uN[N], y: uN[N]) -> uN[N] {
+  if x > y { x } else { y }
+}
 
 fn foo(a: u32, b: u16) -> u64 {
-  std::umax<u32:64>(a as u64, b as u64)
+  umax<u32:64>(a as u64, b as u64)
 }
 ```
 
@@ -53,10 +56,12 @@ are.
 Parametric inference:
 
 ```dslx
-import std;
+fn umax<N: u32>(x: uN[N], y: uN[N]) -> uN[N] {
+  if x > y { x } else { y }
+}
 
 fn foo(a: u32, b: u16) -> u64 {
-  std::umax(a as u64, b as u64)
+  umax(a as u64, b as u64)
 }
 ```
 

xls/dslx/ir_convert/function_converter.cc

@@ -960,12 +960,15 @@ absl::Status FunctionConverter::HandleBuiltinCheckedCast(
       int64_t old_bit_count,
       std::get<InterpValue>(input_bit_count_ctd.value()).GetBitValueViaSign());
 
-  if (dynamic_cast<ArrayType*>(output_type.get()) != nullptr ||
-      dynamic_cast<ArrayType*>(input_type.get()) != nullptr) {
+  std::optional<BitsLikeProperties> output_bits_like =
+      GetBitsLike(*output_type);
+  std::optional<BitsLikeProperties> input_bits_like = GetBitsLike(*input_type);
+
+  if (!output_bits_like.has_value() || !input_bits_like.has_value()) {
     return IrConversionErrorStatus(
         node->span(),
-        absl::StrFormat("CheckedCast to and from array "
-                        "is not currently supported for IR conversion; "
+        absl::StrFormat("CheckedCast is only supported for bits-like types in "
+                        "IR conversion; "
                         "attempted checked cast from: %s to: %s",
                         input_type->ToString(), output_type->ToString()),
         file_table());

xls/dslx/stdlib/apfloat.x

@@ -1503,7 +1503,7 @@ fn test_fp_lt_2() {
 fn to_signed_or_unsigned_int<RESULT_SZ: u32, RESULT_SIGNED: bool, EXP_SZ: u32, FRACTION_SZ: u32>
     (x: APFloat<EXP_SZ, FRACTION_SZ>) -> xN[RESULT_SIGNED][RESULT_SZ] {
     const WIDE_FRACTION: u32 = FRACTION_SZ + u32:1;
-    const MAX_FRACTION_SZ: u32 = std::umax(RESULT_SZ, WIDE_FRACTION);
+    const MAX_FRACTION_SZ: u32 = std::max(RESULT_SZ, WIDE_FRACTION);
 
     const INT_MIN = if RESULT_SIGNED {
         (uN[MAX_FRACTION_SZ]:1 << (RESULT_SZ - u32:1))  // or rather, its negative.

xls/dslx/stdlib/std.x

@@ -90,74 +90,68 @@ fn unsigned_max_value_test() {
     assert_eq(u32:0xffffffff, unsigned_max_value<u32:32>());
 }
 
-// Returns the maximum of two signed integers.
-pub fn smax<N: u32>(x: sN[N], y: sN[N]) -> sN[N] { if x > y { x } else { y } }
+// Returns the maximum of two (signed or unsigned) integers.
+pub fn max<S: bool, N: u32>(x: xN[S][N], y: xN[S][N]) -> xN[S][N] { if x > y { x } else { y } }
 
 #[test]
-fn smax_test() {
-    assert_eq(s2:0, smax(s2:0, s2:0));
-    assert_eq(s2:1, smax(s2:-1, s2:1));
-    assert_eq(s7:-3, smax(s7:-3, s7:-6));
+fn max_test_signed() {
+    assert_eq(s2:0, max(s2:0, s2:0));
+    assert_eq(s2:1, max(s2:-1, s2:1));
+    assert_eq(s7:-3, max(s7:-3, s7:-6));
 }
 
-// Returns the maximum of two unsigned integers.
-pub fn umax<N: u32>(x: uN[N], y: uN[N]) -> uN[N] { if x > y { x } else { y } }
-
 #[test]
-fn umax_test() {
-    assert_eq(u1:1, umax(u1:1, u1:0));
-    assert_eq(u1:1, umax(u1:1, u1:1));
-    assert_eq(u2:3, umax(u2:3, u2:2));
+fn max_test_unsigned() {
+    assert_eq(u1:1, max(u1:1, u1:0));
+    assert_eq(u1:1, max(u1:1, u1:1));
+    assert_eq(u2:3, max(u2:3, u2:2));
 }
 
-// Returns the maximum of two signed integers.
-pub fn smin<N: u32>(x: sN[N], y: sN[N]) -> sN[N] { if x < y { x } else { y } }
+// Returns the minimum of two (signed or unsigned) integers.
+pub fn min<S: bool, N: u32>(x: xN[S][N], y: xN[S][N]) -> xN[S][N] { if x < y { x } else { y } }
 
 #[test]
-fn smin_test() {
-    assert_eq(s1:0, smin(s1:0, s1:0));
-    assert_eq(s1:-1, smin(s1:0, s1:1));
-    assert_eq(s1:-1, smin(s1:1, s1:0));
-    assert_eq(s1:-1, smin(s1:1, s1:1));
-
-    assert_eq(s2:-2, smin(s2:0, s2:-2));
-    assert_eq(s2:-1, smin(s2:0, s2:-1));
-    assert_eq(s2:0, smin(s2:0, s2:0));
-    assert_eq(s2:0, smin(s2:0, s2:1));
+fn min_test_unsigned() {
+    assert_eq(u1:0, min(u1:1, u1:0));
+    assert_eq(u1:1, min(u1:1, u1:1));
+    assert_eq(u2:2, min(u2:3, u2:2));
+}
 
-    assert_eq(s2:-2, smin(s2:1, s2:-2));
-    assert_eq(s2:-1, smin(s2:1, s2:-1));
-    assert_eq(s2:0, smin(s2:1, s2:0));
-    assert_eq(s2:1, smin(s2:1, s2:1));
+#[test]
+fn min_test_signed() {
+    assert_eq(s1:0, min(s1:0, s1:0));
+    assert_eq(s1:-1, min(s1:0, s1:1));
+    assert_eq(s1:-1, min(s1:1, s1:0));
+    assert_eq(s1:-1, min(s1:1, s1:1));
 
-    assert_eq(s2:-2, smin(s2:-2, s2:-2));
-    assert_eq(s2:-2, smin(s2:-2, s2:-1));
-    assert_eq(s2:-2, smin(s2:-2, s2:0));
-    assert_eq(s2:-2, smin(s2:-2, s2:1));
+    assert_eq(s2:-2, min(s2:0, s2:-2));
+    assert_eq(s2:-1, min(s2:0, s2:-1));
+    assert_eq(s2:0, min(s2:0, s2:0));
+    assert_eq(s2:0, min(s2:0, s2:1));
 
-    assert_eq(s2:-2, smin(s2:-1, s2:-2));
-    assert_eq(s2:-1, smin(s2:-1, s2:-1));
-    assert_eq(s2:-1, smin(s2:-1, s2:0));
-    assert_eq(s2:-1, smin(s2:-1, s2:1));
-}
+    assert_eq(s2:-2, min(s2:1, s2:-2));
+    assert_eq(s2:-1, min(s2:1, s2:-1));
+    assert_eq(s2:0, min(s2:1, s2:0));
+    assert_eq(s2:1, min(s2:1, s2:1));
 
-// Returns the minimum of two unsigned integers.
-pub fn umin<N: u32>(x: uN[N], y: uN[N]) -> uN[N] { if x < y { x } else { y } }
+    assert_eq(s2:-2, min(s2:-2, s2:-2));
+    assert_eq(s2:-2, min(s2:-2, s2:-1));
+    assert_eq(s2:-2, min(s2:-2, s2:0));
+    assert_eq(s2:-2, min(s2:-2, s2:1));
 
-#[test]
-fn umin_test() {
-    assert_eq(u1:0, umin(u1:1, u1:0));
-    assert_eq(u1:1, umin(u1:1, u1:1));
-    assert_eq(u2:2, umin(u2:3, u2:2));
+    assert_eq(s2:-2, min(s2:-1, s2:-2));
+    assert_eq(s2:-1, min(s2:-1, s2:-1));
+    assert_eq(s2:-1, min(s2:-1, s2:0));
+    assert_eq(s2:-1, min(s2:-1, s2:1));
 }
 
 // Returns unsigned add of x (N bits) and y (M bits) as a max(N,M)+1 bit value.
-pub fn uadd<N: u32, M: u32, R: u32 = {umax(N, M) + u32:1}>(x: uN[N], y: uN[M]) -> uN[R] {
+pub fn uadd<N: u32, M: u32, R: u32 = {max(N, M) + u32:1}>(x: uN[N], y: uN[M]) -> uN[R] {
     (x as uN[R]) + (y as uN[R])
 }
 
 // Returns signed add of x (N bits) and y (M bits) as a max(N,M)+1 bit value.
-pub fn sadd<N: u32, M: u32, R: u32 = {umax(N, M) + u32:1}>(x: sN[N], y: sN[M]) -> sN[R] {
+pub fn sadd<N: u32, M: u32, R: u32 = {max(N, M) + u32:1}>(x: sN[N], y: sN[M]) -> sN[R] {
     (x as sN[R]) + (y as sN[R])
 }
 
@@ -773,7 +767,7 @@ fn test_to_unsigned() {
 //  let result : (bool, u16) = uadd_with_overflow<u32:16>(x, y);
 //
 pub fn uadd_with_overflow
-    <V: u32, N: u32, M: u32, MAX_N_M: u32 = {umax(N, M)}, MAX_N_M_V: u32 = {umax(MAX_N_M, V)}>
+    <V: u32, N: u32, M: u32, MAX_N_M: u32 = {max(N, M)}, MAX_N_M_V: u32 = {max(MAX_N_M, V)}>
     (x: uN[N], y: uN[M]) -> (bool, uN[V]) {
 
     let x_extended = widening_cast<uN[MAX_N_M_V + u32:1]>(x);
@@ -801,47 +795,48 @@ fn test_uadd_with_overflow() {
 }
 
 // Extract bits given a fixed-point integer with a constant offset.
-//   i.e. let x_extended = x as uN[max(unsigned_sizeof(x) + fixed_shift, to_exclusive)];
-//        (x_extended << fixed_shift)[from_inclusive:to_exclusive]
+//   i.e. let x_extended = x as uN[max(unsigned_sizeof(x) + FIXED_SHIFT, TO_EXCLUSIVE)];
+//        (x_extended << FIXED_SHIFT)[FROM_INCLUSIVE:TO_EXCLUSIVE]
 //
 // This function behaves as-if x has reasonably infinite precision so that
-// the result is zero-padded if from_inclusive or to_exclusive are out of
+// the result is zero-padded if FROM_INCLUSIVE or TO_EXCLUSIVE are out of
 // range of the original x's bitwidth.
 //
-// If to_exclusive <= from_exclusive, the result will be a zero-bit uN[0].
+// If TO_EXCLUSIVE <= FROM_INCLUSIVE, the result will be a zero-bit uN[0].
 pub fn extract_bits
-    <from_inclusive: u32, to_exclusive: u32, fixed_shift: u32, N: u32,
-     extract_width: u32 = {smax(s32:0, to_exclusive as s32 - from_inclusive as s32) as u32}>
-    (x: uN[N]) -> uN[extract_width] {
-    if to_exclusive <= from_inclusive {
-        uN[extract_width]:0
+    <FROM_INCLUSIVE: u32, TO_EXCLUSIVE: u32, FIXED_SHIFT: u32, N: u32,
+     EXTRACT_WIDTH: u32 = {max(s32:0, TO_EXCLUSIVE as s32 - FROM_INCLUSIVE as s32) as u32}>
+    (x: uN[N]) -> uN[EXTRACT_WIDTH] {
+    if TO_EXCLUSIVE <= FROM_INCLUSIVE {
+        uN[EXTRACT_WIDTH]:0
     } else {
         // With a non-zero fixed width, all lower bits of index < fixed_shift are
         // are zero.
         let lower_bits =
-            uN[checked_cast<u32>(smax(s32:0, fixed_shift as s32 - from_inclusive as s32))]:0;
+            uN[checked_cast<u32>(max(s32:0, FIXED_SHIFT as s32 - FROM_INCLUSIVE as s32))]:0;
 
         // Based on the input of N bits and a fixed shift, there are an effective
         // count of N + fixed_shift known bits.  All bits of index >
         // N + fixed_shift - 1 are zero's.
         const UPPER_BIT_COUNT = checked_cast<u32>(
-            smax(s32:0, N as s32 + fixed_shift as s32 - to_exclusive as s32 - s32:1));
-        let upper_bits = uN[UPPER_BIT_COUNT]:0;
+            max(s32:0, N as s32 + FIXED_SHIFT as s32 - TO_EXCLUSIVE as s32 - s32:1));
+        const UPPER_BITS = uN[UPPER_BIT_COUNT]:0;
 
-        if fixed_shift < from_inclusive {
+        if FIXED_SHIFT < FROM_INCLUSIVE {
             // The bits extracted start within or after the middle span.
             //  upper_bits ++ middle_bits
-            let middle_bits = upper_bits ++
-                              x[smin(from_inclusive as s32 - fixed_shift as s32, N as s32)
-                                :smin(to_exclusive as s32 - fixed_shift as s32, N as s32)];
-            (upper_bits ++ middle_bits) as uN[extract_width]
-        } else if fixed_shift <= to_exclusive {
+            const FROM: s32 = min(FROM_INCLUSIVE as s32 - FIXED_SHIFT as s32, N as s32);
+            const TO: s32 = min(TO_EXCLUSIVE as s32 - FIXED_SHIFT as s32, N as s32);
+            let middle_bits = UPPER_BITS ++ x[FROM:TO];
+            (UPPER_BITS ++ middle_bits) as uN[EXTRACT_WIDTH]
+        } else if FIXED_SHIFT <= TO_EXCLUSIVE {
             // The bits extracted start within the fixed_shift span.
-            let middle_bits = x[0:smin(to_exclusive as s32 - fixed_shift as s32, N as s32)];
+            const TO: s32 = min(TO_EXCLUSIVE as s32 - FIXED_SHIFT as s32, N as s32);
+            let middle_bits = x[0:TO];
 
-            (upper_bits ++ middle_bits ++ lower_bits) as uN[extract_width]
+            (UPPER_BITS ++ middle_bits ++ lower_bits) as uN[EXTRACT_WIDTH]
         } else {
-            uN[extract_width]:0
+            uN[EXTRACT_WIDTH]:0
         }
     }
 }
@@ -928,7 +923,7 @@ pub fn umul_with_overflow
     <V: u32, N: u32, M: u32, N_lower_bits: u32 = {N >> u32:1},
      N_upper_bits: u32 = {N - N_lower_bits}, M_lower_bits: u32 = {M >> u32:1},
      M_upper_bits: u32 = {M - M_lower_bits},
-     Min_N_M_lower_bits: u32 = {umin(N_lower_bits, M_lower_bits)}, N_Plus_M: u32 = {N + M}>
+     Min_N_M_lower_bits: u32 = {min(N_lower_bits, M_lower_bits)}, N_Plus_M: u32 = {N + M}>
     (x: uN[N], y: uN[M]) -> (bool, uN[V]) {
     // Break x and y into two halves.
     // x = x1 ++ x0,

xls/dslx/tests/BUILD

@@ -185,6 +185,10 @@ dslx_lang_test(name = "xn_type_equivalence")
 
 dslx_lang_test(name = "xn_signedness_properties")
 
+dslx_lang_test(name = "xn_slice_bounds")
+
+dslx_lang_test(name = "xn_widening_cast")
+
 dslx_lang_test(
     name = "parametric_shift",
     # TODO(leary): 2023-08-14 Runs into "cannot translate zero length bitvector

xls/dslx/tests/errors/error_modules_test.py

@@ -873,8 +873,8 @@ def test_equals_rhs_undefined_nameref(self):
 
   def test_umin_type_mismatch(self):
     stderr = self._run('xls/dslx/tests/errors/umin_type_mismatch.x')
-    self.assertIn('umin_type_mismatch.x:21:12-21:27', stderr)
-    self.assertIn('XlsTypeError: uN[N] vs uN[8]', stderr)
+    self.assertIn('umin_type_mismatch.x:21:13-21:28', stderr)
+    self.assertIn('saw: 42; then: 8', stderr)
 
   def test_diag_block_with_trailing_semi(self):
     stderr = self._run(

xls/dslx/tests/errors/spawn_wrong_argc.x

@@ -19,7 +19,7 @@ pub proc foo {
   config () { () }
 
   next(state: ()) {
-    std::umin(u32:1, u32:2);
+    std::min(u32:1, u32:2);
     ()
   }
 }
@@ -37,7 +37,7 @@ proc test_case {
   }
 
   next(state: ()) {
-    std::umin(u32:1, u32:2);
+    std::min(u32:1, u32:2);
     let tok = send(join(), terminator, true);
     ()
   }

xls/dslx/tests/errors/umin_type_mismatch.x

@@ -18,5 +18,5 @@ const MY_U32 = u42:42;
 const MY_U8 = u8:42;
 
 fn f() -> u32 {
-  std::umin(MY_U32, MY_U8)
+    std::min(MY_U32, MY_U8)
 }

xls/dslx/tests/xn_slice_bounds.x

@@ -0,0 +1,33 @@
+// Copyright 2025 The XLS Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+const S = true;
+const N = u32:32;
+
+type MyS32 = xN[S][N];
+
+fn from_to(x: u32) -> u8 { x[MyS32:0:MyS32:8] }
+
+fn to(x: u32) -> u8 { x[:MyS32:8] }
+
+fn from(x: u32) -> u8 { x[MyS32:-8:] }
+
+fn main(x: u32) -> u8[3] { [from_to(x), to(x), from(x)] }
+
+#[test]
+fn test_main() {
+    assert_eq(from_to(u32:0x12345678), u8:0x78);
+    assert_eq(to(u32:0x12345678), u8:0x78);
+    assert_eq(from(u32:0x12345678), u8:0x12);
+}

xls/dslx/tests/xn_widening_cast.x

@@ -0,0 +1,17 @@
+// Copyright 2025 The XLS Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import std;
+
+fn main(x: u7, y: u7) -> u32 { widening_cast<u32>(std::max(x, y)) }