[PATCH roland/arm-setjmp-iwmmxt] ARM_ASSUME_NO_IWMMXT

[Roland McGrath <roland at hack dot frob dot com>]

This completes what I intend to do as far as getting the Linuxism of HWCAP
bits out of OS-independent ARM code.  It doesn't actually excise the
Linuxisms from setjmp/longjmp, which seemed like it would be a real hassle
to abstract.  Instead, it lets an OS-specific arm-features.h file define
the macro ARM_ASSUME_NO_IWMMXT to avoid the iWMMXt code in setjmp/longjmp.
If this is defined and __SOFTFP__ is not defined, then it doesn't need any
HWCAP bit magic at all.

The new macro is never set by existing (i.e. Linux) configurations.
I intend to define it in a new non-Unix port I'm working on.

Just did the basic compile test.


Thanks,
Roland


ports/ChangeLog.arm
	* sysdeps/arm/arm-features.h: Document ARM_ASSUME_NO_IWMMXT.
	* sysdeps/arm/setjmp.S: Include <arm-features.h>.
	[!ARM_ASSUME_NO_IWMMXT || __SOFTFP__]: Conditionalize hwcap
	fetching bits on this.
	[!ARM_ASSUME_NO_IWMMXT]: Conditionalize iWMMXt register use on this.
	* sysdeps/arm/__longjmp.S: Likewise.


diff --git a/ports/sysdeps/arm/__longjmp.S b/ports/sysdeps/arm/__longjmp.S
index aa5cf74..b3c2860 100644
--- a/ports/sysdeps/arm/__longjmp.S
+++ b/ports/sysdeps/arm/__longjmp.S
@@ -21,6 +21,7 @@
 #define _ASM
 #include <bits/setjmp.h>
 #include <rtld-global-offsets.h>
+#include <arm-features.h>
 
 /* __longjmp(jmpbuf, val) */
 
@@ -46,23 +47,29 @@ ENTRY (__longjmp)
 	cfi_restore (sp)
 	cfi_restore (lr)
 
-#ifdef IS_IN_rtld
+#if !defined ARM_ASSUME_NO_IWMMXT || defined __SOFTFP__
+# define NEED_HWCAP 1
+#endif
+
+#ifdef NEED_HWCAP
+# ifdef IS_IN_rtld
 	ldr	a2, 1f
 	ldr	a3, .Lrtld_local_ro
 0:	add	a2, pc, a2
 	add	a2, a2, a3
 	ldr	a2, [a2, #RTLD_GLOBAL_RO_DL_HWCAP_OFFSET]
-#else
-#ifdef PIC
+# else
+#  ifdef PIC
 	ldr	a2, 1f
 	ldr	a3, .Lrtld_global_ro
 0:	add	a2, pc, a2
 	ldr	a2, [a2, a3]
 	ldr	a2, [a2, #RTLD_GLOBAL_RO_DL_HWCAP_OFFSET]
-#else
+#  else
 	ldr	a2, .Lhwcap
 	ldr	a2, [a2, #0]
-#endif
+#  endif
+# endif
 #endif
 
 #ifdef __SOFTFP__
@@ -79,6 +86,7 @@ ENTRY (__longjmp)
 	mcr	p10, 7, a3, cr1, cr0, 0
 .Lno_vfp:
 
+#ifndef ARM_ASSUME_NO_IWMMXT
 	tst	a2, #HWCAP_ARM_IWMMXT
 	beq	.Lno_iwmmxt
 
@@ -91,22 +99,25 @@ ENTRY (__longjmp)
 	ldcl	p1, cr14, [r12], #8
 	ldcl	p1, cr15, [r12], #8
 .Lno_iwmmxt:
+#endif
 
 	DO_RET(lr)
 
-#ifdef IS_IN_rtld
+#ifdef NEED_HWCAP
+# ifdef IS_IN_rtld
 1:	.long	_GLOBAL_OFFSET_TABLE_ - 0b - 8
 .Lrtld_local_ro:
 	.long	C_SYMBOL_NAME(_rtld_local_ro)(GOTOFF)
-#else
-#ifdef PIC
+# else
+#  ifdef PIC
 1:	.long	_GLOBAL_OFFSET_TABLE_ - 0b - 8
 .Lrtld_global_ro:
 	.long	C_SYMBOL_NAME(_rtld_global_ro)(GOT)
-#else
+#  else
 .Lhwcap:
 	.long	C_SYMBOL_NAME(_dl_hwcap)
-#endif
+#  endif
+# endif
 #endif
 
 END (__longjmp)
diff --git a/ports/sysdeps/arm/arm-features.h b/ports/sysdeps/arm/arm-features.h
index 0f99b3a..41befb5 100644
--- a/ports/sysdeps/arm/arm-features.h
+++ b/ports/sysdeps/arm/arm-features.h
@@ -31,4 +31,9 @@
 # define ARM_HAVE_VFP	1
 #endif
 
+/* An OS-specific arm-features.h file may define ARM_ASSUME_NO_IWMMXT
+   to indicate at compile time that iWMMXt hardware is never present
+   at runtime (or that we never care about its state) and so need not
+   be checked for.  */
+
 #endif  /* arm-features.h */
diff --git a/ports/sysdeps/arm/setjmp.S b/ports/sysdeps/arm/setjmp.S
index 9bfacc1..dbd59dd 100644
--- a/ports/sysdeps/arm/setjmp.S
+++ b/ports/sysdeps/arm/setjmp.S
@@ -21,6 +21,7 @@
 #define _ASM
 #include <bits/setjmp.h>
 #include <rtld-global-offsets.h>
+#include <arm-features.h>
 
 ENTRY (__sigsetjmp)
 	mov	ip, r0
@@ -28,24 +29,30 @@ ENTRY (__sigsetjmp)
 	/* Save registers */
 	stmia	ip!, {v1-v6, sl, fp, sp, lr}
 
+#if !defined ARM_ASSUME_NO_IWMMXT || defined __SOFTFP__
+# define NEED_HWCAP 1
+#endif
+
+#ifdef NEED_HWCAP
 	/* Check if we have a VFP unit.  */
-#ifdef IS_IN_rtld
+# ifdef IS_IN_rtld
 	ldr	a3, 1f
 	ldr	a4, .Lrtld_local_ro
 0:	add	a3, pc, a3
 	add	a3, a3, a4
 	ldr	a3, [a3, #RTLD_GLOBAL_RO_DL_HWCAP_OFFSET]
-#else
-#ifdef PIC
+# else
+#  ifdef PIC
 	ldr	a3, 1f
 	ldr	a4, .Lrtld_global_ro
 0:	add	a3, pc, a3
 	ldr	a3, [a3, a4]
 	ldr	a3, [a3, #RTLD_GLOBAL_RO_DL_HWCAP_OFFSET]
-#else
+#  else
 	ldr	a3, .Lhwcap
 	ldr	a3, [a3, #0]
-#endif
+#  endif
+# endif
 #endif
 
 #ifdef __SOFTFP__
@@ -64,6 +71,7 @@ ENTRY (__sigsetjmp)
 	str	a4, [ip], #4
 .Lno_vfp:
 
+#ifndef ARM_ASSUME_NO_IWMMXT
 	tst	a3, #HWCAP_ARM_IWMMXT
 	beq	.Lno_iwmmxt
 
@@ -76,23 +84,26 @@ ENTRY (__sigsetjmp)
 	stcl	p1, cr14, [r12], #8
 	stcl	p1, cr15, [r12], #8
 .Lno_iwmmxt:
+#endif
 
 	/* Make a tail call to __sigjmp_save; it takes the same args.  */
 	B	PLTJMP(C_SYMBOL_NAME(__sigjmp_save))
 
-#ifdef IS_IN_rtld
+#ifdef NEED_HWCAP
+# ifdef IS_IN_rtld
 1:	.long	_GLOBAL_OFFSET_TABLE_ - 0b - 8
 .Lrtld_local_ro:
 	.long	C_SYMBOL_NAME(_rtld_local_ro)(GOTOFF)
-#else
-#ifdef PIC
+# else
+#  ifdef PIC
 1:	.long	_GLOBAL_OFFSET_TABLE_ - 0b - 8
 .Lrtld_global_ro:
 	.long	C_SYMBOL_NAME(_rtld_global_ro)(GOT)
-#else
+#  else
 .Lhwcap:
 	.long	C_SYMBOL_NAME(_dl_hwcap)
-#endif
+#  endif
+# endif
 #endif
 
 END (__sigsetjmp)