[PATCH] arm: Update strcpy.c to use UAL syntax.

Ian Tessier via newlib newlib@sourceware.org
Wed Jul 19 21:02:00 GMT 2017

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.
 newlib/libc/machine/arm/strcpy.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/newlib/libc/machine/arm/strcpy.c b/newlib/libc/machine/arm/strcpy.c
index f1205b9c1..154451110 100644
--- a/newlib/libc/machine/arm/strcpy.c
+++ b/newlib/libc/machine/arm/strcpy.c
@@ -42,6 +42,7 @@ char* __attribute__((naked))
 strcpy (char* dst, const char* src)
   asm (
+      ".syntax unified\n\t"
 #if !(defined(__OPTIMIZE_SIZE__) || defined (PREFER_SIZE_OVER_SPEED) || \
       (defined (__thumb__) && !defined (__thumb2__)))
 #ifdef _ISA_ARM_7
@@ -127,15 +128,15 @@ strcpy (char* dst, const char* src)
 #ifdef __ARMEB__
        "tst	r2, #0xff00\n\t"
        "iteet	ne\n\t"
-       "strneh	r2, [ip], #2\n\t"
+       "strhne	r2, [ip], #2\n\t"
        "lsreq	r2, r2, #8\n\t"
-       "streqb	r2, [ip]\n\t"
+       "strbeq	r2, [ip]\n\t"
        "tstne	r2, #0xff\n\t"
        "tst	r2, #0xff\n\t"
        "itet	ne\n\t"
-       "strneh	r2, [ip], #2\n\t"
-       "streqb	r2, [ip]\n\t"
+       "strhne	r2, [ip], #2\n\t"
+       "strbeq	r2, [ip]\n\t"
        "tstne	r2, #0xff00\n\t"
        "bne	5b\n\t"
@@ -162,9 +163,9 @@ strcpy (char* dst, const char* src)
        "mov	r3, r0\n\t"
        "ldrb	r2, [r1]\n\t"
-       "add	r1, r1, #1\n\t"
+       "adds	r1, #1\n\t"
        "strb	r2, [r3]\n\t"
-       "add	r3, r3, #1\n\t"
+       "adds	r3, #1\n\t"
        "cmp	r2, #0\n\t"
        "bne	1b\n\t"
        "bx	lr\n\t"

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