[Pkg-rust-maintainers] Bug#898982: rustc: Please re-add workaround for LLVM bug 11663

[John Paul Adrian Glaubitz]

For reference, the patch in question is:

>From 7e62cd4e886a0e3f08e710e0625a7bed9ccbdf51 Mon Sep 17 00:00:00 2001
From: John Paul Adrian Glaubitz <glaubitz at physik.fu-berlin.de>
Date: Tue, 30 Jan 2018 03:00:16 +0100
Subject: [PATCH] Re-add workaround for LLVM bug 11663

---
 lib/builtins/int_lib.h | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/lib/builtins/int_lib.h b/lib/builtins/int_lib.h
index 9d09e2dc9..0b6266630 100644
--- a/lib/builtins/int_lib.h
+++ b/lib/builtins/int_lib.h
@@ -77,6 +77,28 @@
 /* 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 been observed on FreeBSD for sparc64 and
+ * mips64 with GCC 4.2.1, and for riscv with GCC 5.2.0.
+ * Presumably it's any version of GCC, and targeting an arch that
+ * does not have dedicated bit counting instructions.
+ */
+#if ((defined(__sparc__) && defined(__arch64__)) || defined(__mips_n64) || defined(__mips_o64) || defined(__riscv__) \
+		|| (defined(_MIPS_SIM) && ((_MIPS_SIM == _ABI64) || (_MIPS_SIM == _ABIO64))))
+si_int __clzsi2(si_int);
+si_int __ctzsi2(si_int);
+#define	__builtin_clz __clzsi2
+#define	__builtin_ctz __ctzsi2
+#endif /* sparc64 || mips_n64 || mips_o64 || riscv */
+
 COMPILER_RT_ABI si_int __paritysi2(si_int a);
 COMPILER_RT_ABI si_int __paritydi2(di_int a);
 


> [1] https://github.com/rust-lang/compiler-rt/commit/7e62cd4e886a0e3f08e710e0625a7bed9ccbdf51.patch

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer - glaubitz at debian.org
`. `'   Freie Universitaet Berlin - glaubitz at physik.fu-berlin.de
  `-    GPG: 62FF 8A75 84E0 2956 9546  0006 7426 3B37 F5B5 F913