+{
+my ($out,$cnt,$max)=("r3","r4","r5");
+my ($tick,$lasttick)=("r6","r7");
+my ($diff,$lastdiff)=("r8","r9");
+
+$code.=<<___;
+.globl .OPENSSL_instrument_bus
+.align 4
+.OPENSSL_instrument_bus:
+ mtctr $cnt
+
+ mftb $lasttick # collect 1st tick
+ li $diff,0
+
+ dcbf 0,$out # flush cache line
+ lwarx $tick,0,$out # load and lock
+ add $tick,$tick,$diff
+ stwcx. $tick,0,$out
+ stwx $tick,0,$out
+
+Loop: mftb $tick
+ sub $diff,$tick,$lasttick
+ mr $lasttick,$tick
+ dcbf 0,$out # flush cache line
+ lwarx $tick,0,$out # load and lock
+ add $tick,$tick,$diff
+ stwcx. $tick,0,$out
+ stwx $tick,0,$out
+ addi $out,$out,4 # ++$out
+ bdnz Loop
+
+ mr r3,$cnt
+ blr
+ .long 0
+ .byte 0,12,0x14,0,0,0,2,0
+ .long 0
+.size .OPENSSL_instrument_bus,.-.OPENSSL_instrument_bus
+
+.globl .OPENSSL_instrument_bus2
+.align 4
+.OPENSSL_instrument_bus2:
+ mr r0,$cnt
+ slwi $cnt,$cnt,2
+
+ mftb $lasttick # collect 1st tick
+ li $diff,0
+
+ dcbf 0,$out # flush cache line
+ lwarx $tick,0,$out # load and lock
+ add $tick,$tick,$diff
+ stwcx. $tick,0,$out
+ stwx $tick,0,$out
+
+ mftb $tick # collect 1st diff
+ sub $diff,$tick,$lasttick
+ mr $lasttick,$tick
+ mr $lastdiff,$diff
+Loop2:
+ dcbf 0,$out # flush cache line
+ lwarx $tick,0,$out # load and lock
+ add $tick,$tick,$diff
+ stwcx. $tick,0,$out
+ stwx $tick,0,$out
+
+ addic. $max,$max,-1
+ beq Ldone2
+
+ mftb $tick
+ sub $diff,$tick,$lasttick
+ mr $lasttick,$tick
+ cmplw 7,$diff,$lastdiff
+ mr $lastdiff,$diff
+
+ mfcr $tick # pull cr
+ not $tick,$tick # flip bits
+ rlwinm $tick,$tick,1,29,29 # isolate flipped eq bit and scale
+
+ sub. $cnt,$cnt,$tick # conditional --$cnt
+ add $out,$out,$tick # conditional ++$out
+ bne Loop2
+
+Ldone2:
+ srwi $cnt,$cnt,2
+ sub r3,r0,$cnt
+ blr
+ .long 0
+ .byte 0,12,0x14,0,0,0,3,0
+ .long 0
+.size .OPENSSL_instrument_bus2,.-.OPENSSL_instrument_bus2
+___
+}