Description: Use native x86_64 instructions on x32
 This patch enables a few native 64-bit integer instructions
 on x32 which are available on this architecture despite using
 32-bit pointers. These instructions are present on x86_64 but
 not on x86 and ghc checks the size of (void *) to determine
 that. This method fails on x32 since despite using 32-bit
 pointers and hence sizeof(void *) == 4, it still uses the
 full x86_64 instruction set and software-emulated variants
 of the aforementioned 64-bit integer instructions are
 therefore not present in the toolchain which will make ghc
 fail to build on x32.
 See: https://ghc.haskell.org/trac/ghc/ticket/11571
 .

Index: ghc-8.0.2/rts/RtsSymbols.c
===================================================================
--- ghc-8.0.2.orig/rts/RtsSymbols.c
+++ ghc-8.0.2/rts/RtsSymbols.c
@@ -857,7 +857,7 @@
 
 
 // 64-bit support functions in libgcc.a
-#if defined(__GNUC__) && SIZEOF_VOID_P <= 4 && !defined(_ABIN32)
+#if defined(__GNUC__) && SIZEOF_VOID_P <= 4 && !defined(_ABIN32) && !(defined(__x86_64__) && defined(__ILP32__))
 #define RTS_LIBGCC_SYMBOLS                             \
       SymI_NeedsProto(__divdi3)                        \
       SymI_NeedsProto(__udivdi3)                       \