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[PATCH] Add _STRING_INLINE_unaligned

From: Wilco Dijkstra <Wilco dot Dijkstra at arm dot com>
To: 'GNU C Library' <libc-alpha at sourceware dot org>
Cc: nd <nd at arm dot com>
Date: Fri, 8 Jan 2016 17:37:46 +0000
Subject: [PATCH] Add _STRING_INLINE_unaligned
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As discussed in https://sourceware.org/ml/libc-alpha/2015-10/msg00403.html ,
the setting of _STRING_ARCH_unaligned currently controls the external
GLIBC ABI as well as selecting the use of unaligned accesses withing GLIBC.

Since _STRING_ARCH_unaligned was recently changed for AArch64, this
would potentially break the ABI in GLIBC 2.23, so split the uses and add
_STRING_INLINE_unaligned to select the string ABI. This setting must be fixed for
each target, while _STRING_ARCH_unaligned may be changed from release to release.

Built and tested on AArch64, x86 and x64. OK for GLIBC 2.23?

ChangeLog:
2016-01-08  Wilco Dijkstra  <wdijkstr@arm.com>

	* bits/string.h (_STRING_INLINE_unaligned): New define.
	* string/string-inlines.c: Use _STRING_INLINE_unaligned.
	* string/bits/string2.h (_STRING_ARCH_unaligned): Remove
	unused conditional includes.
	* sysdeps/aarch64/bits/string.h (_STRING_INLINE_unaligned): Add define.
	* sysdeps/m68k/m680x0/m68020/bits/string.h
	(_STRING_INLINE_unaligned): Likewise.
	* sysdeps/sparc/bits/string.h (_STRING_INLINE_unaligned): Likewise.
	* sysdeps/s390/bits/string.h (_STRING_INLINE_unaligned): Likewise.
	* sysdeps/x86/bits/string.h (_STRING_INLINE_unaligned): Likewise.


diff --git a/bits/string.h b/bits/string.h
index b88a6bc601803f68a19531d86ce7acdaec65b93b..738d9994a6d4b8df0899a45171fd467156f0fec1 100644
--- a/bits/string.h
+++ b/bits/string.h
@@ -11,4 +11,11 @@
 /* Define if architecture can access unaligned multi-byte variables.  */
 #define _STRING_ARCH_unaligned   0
 
+/* Define whether to use the unaligned string inline ABI.
+   The string inline functions are an external ABI, thus cannot be changed
+   after the first release of a new target (unlike _STRING_ARCH_unaligned
+   which may be changed from release to release).  Targets must support
+   unaligned accesses in hardware if either define is set to true.  */
+#define _STRING_INLINE_unaligned   0
+
 #endif /* bits/string.h */
diff --git a/string/bits/string2.h b/string/bits/string2.h
index f8ea1f9538c19427edae933a9c2fcf111b226bb5..cff529728b7d31f207c6c43aedae4a1b0df4b4b4 100644
--- a/string/bits/string2.h
+++ b/string/bits/string2.h
@@ -46,13 +46,6 @@
 # endif
 #endif
 
-#if _STRING_ARCH_unaligned
-/* If we can do unaligned memory accesses we must know the endianess.  */
-# include <endian.h>
-# include <bits/types.h>
-
-#endif
-
 /* Dereferencing a pointer arg to run sizeof on it fails for the void
    pointer case, so we use this instead.
    Note that __x is evaluated twice. */
diff --git a/string/string-inlines.c b/string/string-inlines.c
index 432d58d8c69771d52e10218cebb8ec125c36faa9..4e91329df22b9c604fff1e833212a8b778c36390 100644
--- a/string/string-inlines.c
+++ b/string/string-inlines.c
@@ -48,7 +48,7 @@ __STRING2_COPY_TYPE (8);
 # undef __STRING2_COPY_TYPE
 
 
-#if _STRING_ARCH_unaligned
+#if _STRING_INLINE_unaligned
 __STRING_INLINE void *__mempcpy_small (void *, char, char, char, char,
 				       __uint16_t, __uint16_t, __uint32_t,
 				       __uint32_t, size_t);
@@ -165,7 +165,7 @@ __mempcpy_small (void *__dest, char __src1,
 }
 #endif
 
-# if _STRING_ARCH_unaligned
+# if _STRING_INLINE_unaligned
 __STRING_INLINE char *
 __strcpy_small (char *__dest,
 		__uint16_t __src0_2, __uint16_t __src4_2,
@@ -270,7 +270,7 @@ __strcpy_small (char *__dest,
 #endif
 
 
-#if _STRING_ARCH_unaligned
+#if _STRING_INLINE_unaligned
 __STRING_INLINE char *
 __stpcpy_small (char *__dest,
 		__uint16_t __src0_2, __uint16_t __src4_2,
diff --git a/sysdeps/aarch64/bits/string.h b/sysdeps/aarch64/bits/string.h
index 5221e69e27610527c89233b3ac74e9c569855694..01421ed28103939a98b0ed3555917ac2aa43254e 100644
--- a/sysdeps/aarch64/bits/string.h
+++ b/sysdeps/aarch64/bits/string.h
@@ -22,3 +22,6 @@
 
 /* AArch64 implementations support efficient unaligned access.  */
 #define _STRING_ARCH_unaligned 1
+
+/* AArch64 uses the aligned string inline ABI.  */
+#define _STRING_INLINE_unaligned 0
diff --git a/sysdeps/m68k/m680x0/m68020/bits/string.h b/sysdeps/m68k/m680x0/m68020/bits/string.h
index b593f4a81f3ad15abe3f3079a8f1350d419caf2b..2fdfc6bf7ba93fd7b73913cf86700facc905bf2b 100644
--- a/sysdeps/m68k/m680x0/m68020/bits/string.h
+++ b/sysdeps/m68k/m680x0/m68020/bits/string.h
@@ -23,3 +23,6 @@
 /* Currently the only purpose of this file is to tell the generic inline
    macros that unaligned memory access is possible.  */
 #define _STRING_ARCH_unaligned	1
+
+/* Use the unaligned string inline ABI.  */
+#define _STRING_INLINE_unaligned 1
diff --git a/sysdeps/s390/bits/string.h b/sysdeps/s390/bits/string.h
index d99039ef89bc797e279ae6f1b37202c1613f3393..7c407f3f4cf5e54972797947d389dc4da998c312 100644
--- a/sysdeps/s390/bits/string.h
+++ b/sysdeps/s390/bits/string.h
@@ -24,6 +24,9 @@
 /* The s390 processors can access unaligned multi-byte variables.  */
 #define _STRING_ARCH_unaligned	1
 
+/* Use the unaligned string inline ABI.  */
+#define _STRING_INLINE_unaligned 1
+
 /* We only provide optimizations if the user selects them and if
    GNU CC is used.  */
 #if !defined __NO_STRING_INLINES && defined __USE_STRING_INLINES \
diff --git a/sysdeps/sparc/bits/string.h b/sysdeps/sparc/bits/string.h
index 4eb94473fbfb4018afd6e92bb3410d6cd2c0032e..1c0603823ec5df48ccaf80388258b7ec92893bc1 100644
--- a/sysdeps/sparc/bits/string.h
+++ b/sysdeps/sparc/bits/string.h
@@ -23,6 +23,9 @@
 /* Define if architecture can access unaligned multi-byte variables.  */
 #define _STRING_ARCH_unaligned   0
 
+/* sparc uses the aligned string inline ABI.  */
+#define _STRING_INLINE_unaligned 0
+
 /* sparc32 and sparc64 strchr(x, '\0') perform better than
    __rawmemchr(x, '\0').  */
 #define _HAVE_STRING_ARCH_strchr 1
diff --git a/sysdeps/x86/bits/string.h b/sysdeps/x86/bits/string.h
index 4973620b83e34ae39cd6f8a599e7c9e7e7eed6c2..30c4517f37a63ad15d7a44bba60b19d441a737fe 100644
--- a/sysdeps/x86/bits/string.h
+++ b/sysdeps/x86/bits/string.h
@@ -23,6 +23,9 @@
 /* The ix86 processors can access unaligned multi-byte variables.  */
 #define _STRING_ARCH_unaligned	1
 
+/* Use the unaligned string inline ABI.  */
+#define _STRING_INLINE_unaligned 1
+
 /* Enable inline functions only for i486 or better when compiling for
    ia32.  */
 #if !defined __x86_64__ && (defined __i486__ || defined __pentium__	      \

Follow-Ups:
- Re: [PATCH] Add _STRING_INLINE_unaligned
  - From: H.J. Lu

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