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authorRoland McGrath <roland@hack.frob.com>2013-11-22 11:39:20 -0800
committerRoland McGrath <roland@hack.frob.com>2013-11-22 11:39:20 -0800
commit068dcfd6758b2f50445d40cfe9d10e4284bd0635 (patch)
tree998c08fbfd6f8aab2723c480ce3723785a541020 /ports
parent12e0e8c65d639fe1e648d116cb5caa434c34ab61 (diff)
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ARM: Fix memcpy computed-jump calculations for ARM_ALWAYS_BX case.
Diffstat (limited to 'ports')
-rw-r--r--ports/ChangeLog.arm8
-rw-r--r--ports/sysdeps/arm/arm-features.h8
-rw-r--r--ports/sysdeps/arm/armv7/multiarch/memcpy_impl.S21
3 files changed, 19 insertions, 18 deletions
diff --git a/ports/ChangeLog.arm b/ports/ChangeLog.arm
index 0dfe5c7884..2ee4444259 100644
--- a/ports/ChangeLog.arm
+++ b/ports/ChangeLog.arm
@@ -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 ...
diff --git a/ports/sysdeps/arm/arm-features.h b/ports/sysdeps/arm/arm-features.h
index 1d4b0f1be9..336b6905af 100644
--- a/ports/sysdeps/arm/arm-features.h
+++ b/ports/sysdeps/arm/arm-features.h
@@ -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. */
diff --git a/ports/sysdeps/arm/armv7/multiarch/memcpy_impl.S b/ports/sysdeps/arm/armv7/multiarch/memcpy_impl.S
index ad43a3db5a..44cecb02d4 100644
--- a/ports/sysdeps/arm/armv7/multiarch/memcpy_impl.S
+++ b/ports/sysdeps/arm/armv7/multiarch/memcpy_impl.S
@@ -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