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PowerPC64 power8 strncpy cfi fixes
- From: Alan Modra <amodra at gmail dot com>
- To: libc-alpha at sourceware dot org
- Date: Fri, 20 Oct 2017 23:36:27 +1030
- Subject: PowerPC64 power8 strncpy cfi fixes
- Authentication-results: sourceware.org; auth=none
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.
diff --git a/sysdeps/powerpc/powerpc64/power8/strncpy.S b/sysdeps/powerpc/powerpc64/power8/strncpy.S
index 150290a..c55e62d 100644
--- a/sysdeps/powerpc/powerpc64/power8/strncpy.S
+++ b/sysdeps/powerpc/powerpc64/power8/strncpy.S
@@ -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.
--
Alan Modra
Australia Development Lab, IBM