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ARM: Fix memcpy computed-jump calculations for ARM_ALWAYS_BX case.

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This commit is contained in:
Roland McGrath 2013-11-22 11:39:20 -08:00
parent 12e0e8c65d
commit 068dcfd675
3 changed files with 19 additions and 18 deletions
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8
ports/ChangeLog.arm
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@ -1,3 +1,11 @@
2013-11-22 Roland McGrath <roland@hack.frob.com>
* sysdeps/arm/armv7/multiarch/memcpy_impl.S
[ARM_ALWAYS_BX] (dispatch_helper): Fix PC computation to properly
account for instructions after the reference to PC given that 'bx'
might actually be expanded to multiple instructions.
* sysdeps/arm/arm-features.h (ARM_BX_NINSNS): Macro removed.
2013-10-30 Mike Frysinger <vapier@gentoo.org>
* sysdeps/arm/configure.in: Moved to ...

8
ports/sysdeps/arm/arm-features.h
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@ -53,14 +53,6 @@
# define ARM_BX_ALIGN_LOG2 2
#endif
/* The number of instructions that 'bx' expands to. A more-specific
arm-features.h that defines 'bx' as a macro should define this to the
number instructions it expands to. This is used only in a context
where the 'bx' expansion won't cross an ARM_BX_ALIGN_LOG2 boundary. */
#ifndef ARM_BX_NINSNS
# define ARM_BX_NINSNS 1
#endif
/* An OS-specific arm-features.h file may define ARM_NO_INDEX_REGISTER to
indicate that the two-register addressing modes must never be used. */

21
ports/sysdeps/arm/armv7/multiarch/memcpy_impl.S
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@ -127,25 +127,26 @@
.purgem dispatch_step
.endm
#else
# if ARM_BX_ALIGN_LOG2 < 4
# if ARM_BX_ALIGN_LOG2 < 3
# error case not handled
# endif
.macro dispatch_helper steps, log2_bytes_per_step
.p2align ARM_BX_ALIGN_LOG2
/* TMP1 gets (max_bytes - bytes_to_copy), where max_bytes is
(STEPS << LOG2_BYTES_PER_STEP).
So this is (steps_to_skip << LOG2_BYTES_PER_STEP). */
rsb tmp1, tmp1, #(\steps << \log2_bytes_per_step)
/* Pad so that the add;bx pair immediately precedes an alignment
boundary. Hence, TMP1=0 will run all the steps. */
.rept (1 << (ARM_BX_ALIGN_LOG2 - 2)) - (2 + ARM_BX_NINSNS)
nop
.endr
So this is (steps_to_skip << LOG2_BYTES_PER_STEP).
Then it needs further adjustment to compensate for the
distance between the PC value taken below (0f + PC_OFS)
and the first step's instructions (1f). */
rsb tmp1, tmp1, #((\steps << \log2_bytes_per_step) \
+ ((1f - PC_OFS - 0f) \
>> (ARM_BX_ALIGN_LOG2 - \log2_bytes_per_step)))
/* Shifting down LOG2_BYTES_PER_STEP gives us the number of
steps to skip, then shifting up ARM_BX_ALIGN_LOG2 gives us
the (byte) distance to add to the PC. */
add tmp1, pc, tmp1, lsl #(ARM_BX_ALIGN_LOG2 - \log2_bytes_per_step)
0: add tmp1, pc, tmp1, lsl #(ARM_BX_ALIGN_LOG2 - \log2_bytes_per_step)
bx tmp1
.p2align ARM_BX_ALIGN_LOG2
1:
.endm
.macro dispatch_7_dword