powerpc, libcpp: Fix gcc build with clang on power8 [PR97163]

libcpp has two specialized altivec implementations of search_line_fast,
one for power8+ and the other one otherwise.
Both use __attribute__((altivec(vector))) and the GCC builtins rather than
altivec.h and the APIs from there, which is fine, but should be restricted
to when libcpp is built with GCC, so that it can be relied on.
The second elif is
and thus e.g. when built with clang it isn't picked, but the first one was
just guarded with
and so according to the bugreporter clang fails miserably on that.

The following patch fixes that by adding the same GCC_VERSION requirement
as the second version.  I don't know where the 4.5 in there comes from and
the exact version doesn't matter that much, as long as it is above 4.2 that
clang pretends to be and smaller or equal to 4.8 as the oldest gcc we
support as bootstrap compiler ATM.
Furthermore, the patch fixes the comment, the version it is talking about is
not pre-GCC 5, but actually the GCC 5+ one.

2020-09-26  Jakub Jelinek  <jakub@redhat.com>

	PR bootstrap/97163
	* lex.c (search_line_fast): Only use _ARCH_PWR8 Altivec version
	for GCC >= 4.5.

diff --git a/libcpp/lex.c b/libcpp/lex.c
index 9aec9e0bd04e72a64a710a3fadb59e9c1913f66b..2fe77d162a2abf62be50f26376adcdf1879bf7c8 100644 (file)
--- a/libcpp/lex.c
+++ b/libcpp/lex.c
@@ -531,11 +531,11 @@ init_vectorized_lexer (void)
   search_line_fast = impl;
 }
 
-#elif defined(_ARCH_PWR8) && defined(__ALTIVEC__)
+#elif (GCC_VERSION >= 4005) && defined(_ARCH_PWR8) && defined(__ALTIVEC__)
 
 /* A vection of the fast scanner using AltiVec vectorized byte compares
    and VSX unaligned loads (when VSX is available).  This is otherwise
-   the same as the pre-GCC 5 version.  */
+   the same as the AltiVec version.  */
 
 ATTRIBUTE_NO_SANITIZE_UNDEFINED
 static const uchar *