Index: lib/builtins/clzdi2.c
===================================================================
--- lib/builtins/clzdi2.c
+++ lib/builtins/clzdi2.c
@@ -16,8 +16,13 @@
 
 /* Returns: the number of leading 0-bits */
 
-#if !defined(__clang__) && (defined(__sparc64__) || defined(__mips64) || defined(__riscv__))
-/* gcc resolves __builtin_clz -> __clzdi2 leading to infinite recursion */
+#if !defined(__clang__) &&                                                     \
+    ((defined(__sparc__) && defined(__arch64__)) ||                            \
+     defined(__mips64) ||                                                      \
+     (defined(__riscv) && __SIZEOF_POINTER__ >= 8))
+/* On 64-bit architectures with neither a native clz instruction nor a native
+ * ctz instruction, gcc resolves __builtin_clz to __clzdi2 rather than
+ * __clzsi2, leading to infinite recursion. */
 #define __builtin_clz(a) __clzsi2(a)
 extern si_int __clzsi2(si_int);
 #endif
Index: lib/builtins/ctzdi2.c
===================================================================
--- lib/builtins/ctzdi2.c
+++ lib/builtins/ctzdi2.c
@@ -16,8 +16,13 @@
 
 /* Returns: the number of trailing 0-bits  */
 
-#if !defined(__clang__) && (defined(__sparc64__) || defined(__mips64) || defined(__riscv__))
-/* gcc resolves __builtin_ctz -> __ctzdi2 leading to infinite recursion */
+#if !defined(__clang__) &&                                                     \
+    ((defined(__sparc__) && defined(__arch64__)) ||                            \
+     defined(__mips64) ||                                                      \
+     (defined(__riscv) && __SIZEOF_POINTER__ >= 8))
+/* On 64-bit architectures with neither a native clz instruction nor a native
+ * ctz instruction, gcc resolves __builtin_ctz to __ctzdi2 rather than
+ * __ctzsi2, leading to infinite recursion. */
 #define __builtin_ctz(a) __ctzsi2(a)
 extern si_int __ctzsi2(si_int);
 #endif