[compiler-rt] r324593 - [builtins] Workaround for infinite recursion in c?zdi2

[Jonas Devlieghere via llvm-commits]

Author: jdevlieghere
Date: Thu Feb  8 03:14:11 2018
New Revision: 324593

URL: http://llvm.org/viewvc/llvm-project?rev=324593&view=rev
Log:
[builtins] Workaround for infinite recursion in c?zdi2

gcc resolves `__builtin_c?z` to `__c?zdi2` which leads to infinite
recursion. This problem has been observed for sparc64, mips64 and riscv.
Presumably this happens whenever an arch without dedicated bit counting
instructions is targeted. This patch provides a workaround.

Differential revision: https://reviews.llvm.org/D42902

Modified:
    compiler-rt/trunk/lib/builtins/clzdi2.c
    compiler-rt/trunk/lib/builtins/ctzdi2.c

Modified: compiler-rt/trunk/lib/builtins/clzdi2.c
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/builtins/clzdi2.c?rev=324593&r1=324592&r2=324593&view=diff
==============================================================================
--- compiler-rt/trunk/lib/builtins/clzdi2.c (original)
+++ compiler-rt/trunk/lib/builtins/clzdi2.c Thu Feb  8 03:14:11 2018
@@ -16,6 +16,12 @@
 
 /* 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 */
+#define __builtin_clz(a) __clzsi2(a)
+extern si_int __clzsi2(si_int);
+#endif
+
 /* Precondition: a != 0 */
 
 COMPILER_RT_ABI si_int

Modified: compiler-rt/trunk/lib/builtins/ctzdi2.c
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/builtins/ctzdi2.c?rev=324593&r1=324592&r2=324593&view=diff
==============================================================================
--- compiler-rt/trunk/lib/builtins/ctzdi2.c (original)
+++ compiler-rt/trunk/lib/builtins/ctzdi2.c Thu Feb  8 03:14:11 2018
@@ -16,6 +16,12 @@
 
 /* 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 */
+#define __builtin_ctz(a) __ctzsi2(a)
+extern si_int __ctzsi2(si_int);
+#endif
+
 /* Precondition: a != 0 */
 
 COMPILER_RT_ABI si_int