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From: Ed Schouten <ed@FreeBSD.org>
Date: Thu, 12 Jan 2012 16:51:56 +0000 (UTC)
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Subject: svn commit: r230021 - head/contrib/compiler-rt/lib
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Author: ed
Date: Thu Jan 12 16:51:56 2012
New Revision: 230021
URL: http://svn.freebsd.org/changeset/base/230021

Log:
  Add a workaround to prevent endless recursion in compiler-rt.
  
  SPARC and MIPS CPUs don't have special instructions to count
  leading/trailing zeroes. The compiler-rt library provides fallback
  rountines for these. The 64-bit routines, __clzdi2 and __ctzdi2, are
  implemented as simple wrappers around the compiler built-in
  __builtin_clz(), assuming these will expand to either 32-bit
  CPU instructions or calls to __clzsi2 and __ctzsi2.
  
  Unfortunately, our GCC 4.2 probably thinks that because the operand is
  stored in a 64-bit register, it might just be a better idea to invoke
  its 64-bit equivalent, simply resulting into endless recursion. Fix this
  by defining __builtin_clz and __builtin_ctz to __clzsi2 and __ctzsi2
  explicitly.

Modified:
  head/contrib/compiler-rt/lib/int_lib.h

Modified: head/contrib/compiler-rt/lib/int_lib.h
==============================================================================
--- head/contrib/compiler-rt/lib/int_lib.h	Thu Jan 12 15:57:03 2012	(r230020)
+++ head/contrib/compiler-rt/lib/int_lib.h	Thu Jan 12 16:51:56 2012	(r230021)
@@ -43,4 +43,24 @@
 /* Include internal utility function declarations. */
 #include "int_util.h"
 
+/*
+ * Workaround for LLVM bug 11663.  Prevent endless recursion in
+ * __c?zdi2(), where calls to __builtin_c?z() are expanded to
+ * __c?zdi2() instead of __c?zsi2().
+ *
+ * Instead of placing this workaround in c?zdi2.c, put it in this
+ * global header to prevent other C files from making the detour
+ * through __c?zdi2() as well.
+ *
+ * This problem has only been observed on FreeBSD for sparc64 and
+ * mips64 with GCC 4.2.1.
+ */
+#if defined(__FreeBSD__) && (defined(__sparc64__) || \
+    defined(__mips_n64) || defined(__mips_o64))
+si_int __clzsi2(si_int);
+si_int __ctzsi2(si_int);
+#define	__builtin_clz	__clzsi2
+#define	__builtin_ctz	__ctzsi2
+#endif
+
 #endif /* INT_LIB_H */