[libc-commits] [libc] [libc] Suppress GCC loop optimization warning (PR #132458)

[Joseph Huber via libc-commits]

https://github.com/jhuber6 updated https://github.com/llvm/llvm-project/pull/132458

>From 7cdeffa47c66a966a5c53ba863f763f2f6a01107 Mon Sep 17 00:00:00 2001
From: Joseph Huber <huberjn at outlook.com>
Date: Fri, 21 Mar 2025 14:20:20 -0500
Subject: [PATCH] [libc] Suppress GCC loop optimization warning

Summary:
This appears to be a false positive on some versions of GCC.
---
 libc/src/__support/big_int.h | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/libc/src/__support/big_int.h b/libc/src/__support/big_int.h
index 85db31d01399a..25dddfef9ca8c 100644
--- a/libc/src/__support/big_int.h
+++ b/libc/src/__support/big_int.h
@@ -790,11 +790,21 @@ struct BigInt {
       remainder[pos] = rem;
     }
 
+    // GCC currently emits a false-positive warning on this for some compilers.
+#ifdef __GNUC__
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Waggressive-loop-optimizations"
+#endif
+
     // Set the remaining lower bits of the remainder.
     for (; pos > 0; --pos) {
       remainder[pos - 1] = val[pos - 1];
     }
 
+#ifdef __GNUC__
+#pragma GCC diagnostic pop
+#endif
+
     *this = quotient;
     return remainder;
   }
@@ -851,8 +861,8 @@ struct BigInt {
       result[i] = lhs[i] OP rhs[i];                                            \
     return result;                                                             \
   }                                                                            \
-  LIBC_INLINE friend constexpr BigInt operator OP##=(BigInt &lhs,              \
-                                                     const BigInt &rhs) {      \
+  LIBC_INLINE friend constexpr BigInt operator OP## =                          \
+      (BigInt & lhs, const BigInt &rhs) {                                      \
     for (size_t i = 0; i < WORD_COUNT; ++i)                                    \
       lhs[i] OP## = rhs[i];                                                    \
     return lhs;                                                                \