feat: implement template meta muli

[naveen106]

fixing issue #129123. More to be done. Not completed.

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[llvmbot]

@llvm/pr-subscribers-libc

Author: Naveen Kumar (naveen106)

Changes

fixing issue #129123. More to be done. Not completed.

---

Full diff: https://github.com/llvm/llvm-project/pull/138654.diff

2 Files Affected:

• (added) CppProperties.json (+21)
• (modified) libc/src/__support/fixed_point/fx_bits.h (+20)

diff --git a/CppProperties.json b/CppProperties.json
new file mode 100644
index 0000000000000..659bf4ea9068f
--- /dev/null
+++ b/CppProperties.json
@@ -0,0 +1,21 @@
+{
+  "configurations": [
+    {
+      "inheritEnvironments": [
+        "msvc_x86"
+      ],
+      "name": "x86-Debug",
+      "includePath": [
+        "${env.INCLUDE}",
+        "${workspaceRoot}\\**"
+      ],
+      "defines": [
+        "WIN32",
+        "_DEBUG",
+        "UNICODE",
+        "_UNICODE"
+      ],
+      "intelliSenseMode": "windows-msvc-x86"
+    }
+  ]
+}
\ No newline at end of file
diff --git a/libc/src/__support/fixed_point/fx_bits.h b/libc/src/__support/fixed_point/fx_bits.h
index b05f46bd34660..974bb8a8f79bd 100644
--- a/libc/src/__support/fixed_point/fx_bits.h
+++ b/libc/src/__support/fixed_point/fx_bits.h
@@ -194,6 +194,26 @@ countls(T f) {
   return cpp::countl_zero(value_bits) - FXRep::SIGN_LEN;
 }
 
+// Multiply an integer with a fixed-point value and return an integer.
+// Overflow behavior is undefined, per ISO 8037.
+template <typename FixedPointT, typename IntT>
+LIBC_INLINE constexpr cpp::enable_if_t <cpp::is_fixed_point_v<FixedPointT> && cpp::is_integral_v<IntT>, IntT > 
+muli(FixedPointT f, IntT i) {
+  
+  using FXRep = FXRep<FixedPointT>;
+  using BitType = typename FXRep::StorageType;
+  BitType fixed_bits = FXBits<FixedPointT>(f).get_bits();
+
+  // Safely promote types to unsigned for multiplication to avoid signed overflow
+  using UnsignedIntT = cpp::make_unsigned_t<IntT>;
+  using UnsignedFixedT = cpp::make_unsigned_t<BitType>;
+
+  auto product = static_cast<UnsignedIntT>(i) * static_cast<UnsignedFixedT>(fixed_bits);
+
+  // Shift back to remove fractional bits
+  return static_cast<IntT>(product >> FXRep::FRAC_LEN);
+}
+
 // fixed-point to integer conversion
 template <typename T, typename XType>
 LIBC_INLINE constexpr cpp::enable_if_t<cpp::is_fixed_point_v<T>, XType>

[PiJoules]

The implementation looks ok, but could you add tests and the relevant build changes so we can ensure it works properly? You can follow what the other fixed point patches do and replace the names appropriately (#133005 for example).

[naveen106]

The implementation looks ok, but could you add tests and the relevant build changes so we can ensure it works properly? You can follow what the other fixed point patches do and replace the names appropriately (#133005 for example).

@PiJoules
Working on it! I have added mulifx functions, working on unit tests now. Inform me if you see something wrong till now.