From 1ce044b732fbae373c0bba4633f3c6f456464379 Mon Sep 17 00:00:00 2001
From: EFanZh <efanzh@gmail.com>
Date: Sat, 22 Nov 2025 18:23:13 +0800
Subject: [PATCH] Add `ilog10` result range hints

---
 library/core/src/num/int_macros.rs            |  10 +-
 library/core/src/num/nonzero.rs               |  10 +-
 .../lib-optimizations/ilog10-range.rs         | 213 ++++++++++++++++++
 3 files changed, 231 insertions(+), 2 deletions(-)
 create mode 100644 tests/codegen-llvm/lib-optimizations/ilog10-range.rs

diff --git a/library/core/src/num/int_macros.rs b/library/core/src/num/int_macros.rs
index 93fdf2823aeb7..69df73f65c677 100644
--- a/library/core/src/num/int_macros.rs
+++ b/library/core/src/num/int_macros.rs
@@ -3520,8 +3520,16 @@ macro_rules! int_impl {
                       without modifying the original"]
         #[inline]
         pub const fn checked_ilog10(self) -> Option<u32> {
+            const MAX_RESULT: u32 = int_log10::$ActualT(<$SelfT>::MAX as $ActualT);
+
             if self > 0 {
-                Some(int_log10::$ActualT(self as $ActualT))
+                let result = int_log10::$ActualT(self as $ActualT);
+
+                // SAFETY: `ilog10` is a monotonically nondecreasing function, so the result for
+                // positive inputs is always in the range [0, `MAX_RESULT`].
+                unsafe { crate::hint::assert_unchecked(result <= MAX_RESULT) };
+
+                Some(result)
             } else {
                 None
             }
diff --git a/library/core/src/num/nonzero.rs b/library/core/src/num/nonzero.rs
index ee375dbaaab2d..0029d826de916 100644
--- a/library/core/src/num/nonzero.rs
+++ b/library/core/src/num/nonzero.rs
@@ -1657,7 +1657,15 @@ macro_rules! nonzero_integer_signedness_dependent_methods {
                       without modifying the original"]
         #[inline]
         pub const fn ilog10(self) -> u32 {
-            super::int_log10::$Int(self.get())
+            const MAX_RESULT: u32 = super::int_log10::$Int(<$Int>::MAX);
+
+            let result = super::int_log10::$Int(self.get());
+
+            // SAFETY: `ilog10` is a monotonically nondecreasing function, so the result for
+            // positive inputs is always in the range [0, `MAX_RESULT`].
+            unsafe { crate::hint::assert_unchecked(result <= MAX_RESULT) };
+
+            result
         }
 
         /// Calculates the midpoint (average) between `self` and `rhs`.
diff --git a/tests/codegen-llvm/lib-optimizations/ilog10-range.rs b/tests/codegen-llvm/lib-optimizations/ilog10-range.rs
new file mode 100644
index 0000000000000..b466855389fb4
--- /dev/null
+++ b/tests/codegen-llvm/lib-optimizations/ilog10-range.rs
@@ -0,0 +1,213 @@
+//! Make sure the compiler knows the result range of `ilog10`.
+
+//@ compile-flags: -O -Z merge-functions=disabled
+
+#![crate_type = "lib"]
+
+use std::num::NonZero;
+
+// Signed integers.
+
+#[no_mangle]
+fn i8_ilog10_range(value: i8) {
+    const MAX_RESULT: u32 = i8::MAX.ilog10();
+
+    // CHECK-LABEL: @i8_ilog10_range(
+    // CHECK-NOT: panic
+    // CHECK: ret void
+    // CHECK-NEXT: }
+    assert!(value <= 0 || value.ilog10() <= MAX_RESULT);
+    assert!(value.checked_ilog10().is_none_or(|result| result <= MAX_RESULT));
+}
+
+#[no_mangle]
+fn i16_ilog10_range(value: i16) {
+    const MAX_RESULT: u32 = i16::MAX.ilog10();
+
+    // CHECK-LABEL: @i16_ilog10_range(
+    // CHECK-NOT: panic
+    // CHECK: ret void
+    // CHECK-NEXT: }
+    assert!(value <= 0 || value.ilog10() <= MAX_RESULT);
+    assert!(value.checked_ilog10().is_none_or(|result| result <= MAX_RESULT));
+}
+
+#[no_mangle]
+fn i32_ilog10_range(value: i32) {
+    const MAX_RESULT: u32 = i32::MAX.ilog10();
+
+    // CHECK-LABEL: @i32_ilog10_range(
+    // CHECK-NOT: panic
+    // CHECK: ret void
+    // CHECK-NEXT: }
+    assert!(value <= 0 || value.ilog10() <= MAX_RESULT);
+    assert!(value.checked_ilog10().is_none_or(|result| result <= MAX_RESULT));
+}
+
+#[no_mangle]
+fn i64_ilog10_range(value: i64) {
+    const MAX_RESULT: u32 = i64::MAX.ilog10();
+
+    // CHECK-LABEL: @i64_ilog10_range(
+    // CHECK-NOT: panic
+    // CHECK: ret void
+    // CHECK-NEXT: }
+    assert!(value <= 0 || value.ilog10() <= MAX_RESULT);
+    assert!(value.checked_ilog10().is_none_or(|result| result <= MAX_RESULT));
+}
+
+#[no_mangle]
+fn i128_ilog10_range(value: i128) {
+    const MAX_RESULT: u32 = i128::MAX.ilog10();
+
+    // CHECK-LABEL: @i128_ilog10_range(
+    // CHECK-NOT: panic
+    // CHECK: ret void
+    // CHECK-NEXT: }
+    assert!(value <= 0 || value.ilog10() <= MAX_RESULT);
+    assert!(value.checked_ilog10().is_none_or(|result| result <= MAX_RESULT));
+}
+
+#[no_mangle]
+fn isize_ilog10_range(value: isize) {
+    const MAX_RESULT: u32 = isize::MAX.ilog10();
+
+    // CHECK-LABEL: @isize_ilog10_range(
+    // CHECK-NOT: panic
+    // CHECK: ret void
+    // CHECK-NEXT: }
+    assert!(value <= 0 || value.ilog10() <= MAX_RESULT);
+    assert!(value.checked_ilog10().is_none_or(|result| result <= MAX_RESULT));
+}
+
+// Unsigned integer types.
+
+#[no_mangle]
+fn u8_ilog10_range(value: u8) {
+    const MAX_RESULT: u32 = u8::MAX.ilog10();
+
+    // CHECK-LABEL: @u8_ilog10_range(
+    // CHECK-NOT: panic
+    // CHECK: ret void
+    // CHECK-NEXT: }
+    assert!(value == 0 || value.ilog10() <= MAX_RESULT);
+    assert!(value.checked_ilog10().is_none_or(|result| result <= MAX_RESULT));
+}
+
+#[no_mangle]
+fn u16_ilog10_range(value: u16) {
+    const MAX_RESULT: u32 = u16::MAX.ilog10();
+
+    // CHECK-LABEL: @u16_ilog10_range(
+    // CHECK-NOT: panic
+    // CHECK: ret void
+    // CHECK-NEXT: }
+    assert!(value == 0 || value.ilog10() <= MAX_RESULT);
+    assert!(value.checked_ilog10().is_none_or(|result| result <= MAX_RESULT));
+}
+
+#[no_mangle]
+fn u32_ilog10_range(value: u32) {
+    const MAX_RESULT: u32 = u32::MAX.ilog10();
+
+    // CHECK-LABEL: @u32_ilog10_range(
+    // CHECK-NOT: panic
+    // CHECK: ret void
+    // CHECK-NEXT: }
+    assert!(value == 0 || value.ilog10() <= MAX_RESULT);
+    assert!(value.checked_ilog10().is_none_or(|result| result <= MAX_RESULT));
+}
+
+#[no_mangle]
+fn u64_ilog10_range(value: u64) {
+    const MAX_RESULT: u32 = u64::MAX.ilog10();
+
+    // CHECK-LABEL: @u64_ilog10_range(
+    // CHECK-NOT: panic
+    // CHECK: ret void
+    // CHECK-NEXT: }
+    assert!(value == 0 || value.ilog10() <= MAX_RESULT);
+    assert!(value.checked_ilog10().is_none_or(|result| result <= MAX_RESULT));
+}
+
+#[no_mangle]
+fn u128_ilog10_range(value: u128) {
+    const MAX_RESULT: u32 = u128::MAX.ilog10();
+
+    // CHECK-LABEL: @u128_ilog10_range(
+    // CHECK-NOT: panic
+    // CHECK: ret void
+    // CHECK-NEXT: }
+    assert!(value == 0 || value.ilog10() <= MAX_RESULT);
+    assert!(value.checked_ilog10().is_none_or(|result| result <= MAX_RESULT));
+}
+
+#[no_mangle]
+fn usize_ilog10_range(value: usize) {
+    const MAX_RESULT: u32 = usize::MAX.ilog10();
+
+    // CHECK-LABEL: @usize_ilog10_range(
+    // CHECK-NOT: panic
+    // CHECK: ret void
+    // CHECK-NEXT: }
+    assert!(value == 0 || value.ilog10() <= MAX_RESULT);
+    assert!(value.checked_ilog10().is_none_or(|result| result <= MAX_RESULT));
+}
+
+// Signed non-zero integers do not have `ilog10` methods.
+
+// Unsigned non-zero integers.
+
+#[no_mangle]
+fn non_zero_u8_ilog10_range(value: NonZero<u8>) {
+    // CHECK-LABEL: @non_zero_u8_ilog10_range(
+    // CHECK-NOT: panic
+    // CHECK: ret void
+    // CHECK-NEXT: }
+    assert!(value.ilog10() <= const { u8::MAX.ilog10() });
+}
+
+#[no_mangle]
+fn non_zero_u16_ilog10_range(value: NonZero<u16>) {
+    // CHECK-LABEL: @non_zero_u16_ilog10_range(
+    // CHECK-NOT: panic
+    // CHECK: ret void
+    // CHECK-NEXT: }
+    assert!(value.ilog10() <= const { u16::MAX.ilog10() });
+}
+
+#[no_mangle]
+fn non_zero_u32_ilog10_range(value: NonZero<u32>) {
+    // CHECK-LABEL: @non_zero_u32_ilog10_range(
+    // CHECK-NOT: panic
+    // CHECK: ret void
+    // CHECK-NEXT: }
+    assert!(value.ilog10() <= const { u32::MAX.ilog10() });
+}
+
+#[no_mangle]
+fn non_zero_u64_ilog10_range(value: NonZero<u64>) {
+    // CHECK-LABEL: @non_zero_u64_ilog10_range(
+    // CHECK-NOT: panic
+    // CHECK: ret void
+    // CHECK-NEXT: }
+    assert!(value.ilog10() <= const { u64::MAX.ilog10() });
+}
+
+#[no_mangle]
+fn non_zero_u128_ilog10_range(value: NonZero<u128>) {
+    // CHECK-LABEL: @non_zero_u128_ilog10_range(
+    // CHECK-NOT: panic
+    // CHECK: ret void
+    // CHECK-NEXT: }
+    assert!(value.ilog10() <= const { u128::MAX.ilog10() });
+}
+
+#[no_mangle]
+fn non_zero_usize_ilog10_range(value: NonZero<usize>) {
+    // CHECK-LABEL: @non_zero_usize_ilog10_range(
+    // CHECK-NOT: panic
+    // CHECK: ret void
+    // CHECK-NEXT: }
+    assert!(value.ilog10() <= const { usize::MAX.ilog10() });
+}