With this change the arm platform can now be fully compiled with Clang.
Tested by comparing the output with GCC 4.8.2, and Clang 4.0, using a
variety of arches, big/little endianness, and arm/thumb mode to verify
the generated assembly output matches between GCC vs Clang with UAL, and
also GCC with UAL vs GCC with non-UAL, for all preprocessor code blocks.
The only difference found is an extra nop at the end of the function
when compiled with GCC using armv7-a/thumb/little-endian/-O2 compared to
Clang. The nop is not emitted when compiled in big-endian mode.
In patch b219285f87 you have a syntax
error in the PLD instruction. The syntax for the pld argument should be
in square brackets as it's a memory address like so: pld [r1]. With
your patch the newlib build fails for armv7-a targets. This patch fixes
the build failures.
Tested by making sure the newlib build completes successfully.
2016-01-26 Kyrylo Tkachov <kyrylo.tkachov@arm.com>
* libc/machine/arm/strcpy.c (strcpy): Fix PLD assembly syntax.
* libc/machine/arm/strlen-stub.c (strlen): Likewise.
LTO can re-order top-level assembly blocks, which can cause this
macro definition to appear after its use (or not at all), causing
compilation failures. On modern toolchains (armv4t+), assembly
should write `bx lr` in all cases, and linkers will transparently
convert them to `mov pc, lr`, allowing us to simply remove the
macro.
(source: https://groups.google.com/forum/#!topic/comp.sys.arm/3l7fVGX-Wug
and verified empirically)
For the armv4.S file, preserve this macro to maximize backwards
compatibility.
LTO can re-order top-level assembly blocks, which can cause this
macro definition to appear after its use (or not at all), causing
compilation failures. As the macro has very few uses, simply removing
it by inlining is a simple fix.
n.b. one of the macro invocations in strlen-stub.c was already
guarded by the relevant #define, so it is simply converted directly
to a pld
* libc/machine/arm/arm_asm.h: New file.
* libc/machine/arm/strlen.c: New file.
* libc/machine/arm/strcpy.c: New file.
* libc/machine/arm/strcmp.c: New file.
* libc/machine/arm/Makefile.am: Add new string routines.
Richard Earnshaw
Ian Tessier via newlib
Kyrill Tkachov
Pat Pannuto
Jeff Johnston