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PowerPC64 power8 strncpy cfi fixes

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cfi info for stack adjust needs to be on the insn doing the adjust.
cfi describing register saves can be anywhere after the save insn but
before the reg is altered.  Fewer locations with cfi result in smaller
cfi programs and possibly slightly faster exception handling.  Thus
the LR cfi_offset move.

The idea behind ajusting sp after restoring regs is to break a
register dependency chain, in this case not be using r1 immediately
after it is modified.

The missing LR cfi_restore meant that code after the blr,
unaligned_lt_16 and other labels, would have cfi that said LR was at
cfa+16, but that code is reached without LR being saved.

	* sysdeps/powerpc/powerpc64/power8/strncpy.S: Move LR cfi.
	Adjust stack after restoring regs.  Add missing LR cfi_restore.

Reviewed-by: Tulio Magno Quites Machado Filho <tuliom@linux.vnet.ibm.com>
This commit is contained in:
Alan Modra 2017-10-23 07:44:50 +10:30
parent 750a0e4967
commit 174935af03
2 changed files with 19 additions and 13 deletions
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5
ChangeLog
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@ -1,3 +1,8 @@
2017-10-23 Alan Modra <amodra@gmail.com>
* sysdeps/powerpc/powerpc64/power8/strncpy.S: Move LR cfi.
Adjust stack after restoring regs. Add missing LR cfi_restore.
2017-10-23 Alan Modra <amodra@gmail.com>
* sysdeps/powerpc/powerpc64/power7/strncpy.S: Decrease FRAMESIZE.

27
sysdeps/powerpc/powerpc64/power8/strncpy.S
View File

@ -241,23 +241,18 @@ L(zero_pad_start_1):
/* Save the link register. */
mflr r0
std r0,16(r1)
cfi_offset(lr, 16)
/* Create the stack frame. */
stdu r1,-FRAMESIZE(r1)
cfi_adjust_cfa_offset(FRAMESIZE)
cfi_offset(lr, 16)
bl MEMSET
#ifndef MEMSET_is_local
nop
#endif
/* Restore the stack frame. */
addi r1,r1,FRAMESIZE
cfi_adjust_cfa_offset(-FRAMESIZE)
/* Restore the link register. */
ld r0,16(r1)
mtlr r0
ld r0,FRAMESIZE+16(r1)
#ifndef USE_AS_STPNCPY
mr r3,r30 /* Restore the return value of strncpy, i.e.:
@ -266,12 +261,18 @@ L(zero_pad_start_1):
#endif
/* Restore non-volatile registers and return. */
ld r26,-48(r1)
ld r27,-40(r1)
ld r28,-32(r1)
ld r29,-24(r1)
ld r30,-16(r1)
ld r31,-8(r1)
ld r26,FRAMESIZE-48(r1)
ld r27,FRAMESIZE-40(r1)
ld r28,FRAMESIZE-32(r1)
ld r29,FRAMESIZE-24(r1)
ld r30,FRAMESIZE-16(r1)
ld r31,FRAMESIZE-8(r1)
/* Restore the stack frame. */
addi r1,r1,FRAMESIZE
cfi_adjust_cfa_offset(-FRAMESIZE)
/* Restore the link register. */
mtlr r0
cfi_restore(lr)
blr
/* The common case where [src]+16 will not cross a 4K page boundary.