2 files changed, 77 insertions, 18 deletions
diff --git a/src/runtime/memclr_ppc64x.s b/src/runtime/memclr_ppc64x.s
index cea42cb70c..90e27482ff 100644
--- a/src/runtime/memclr_ppc64x.s
+++ b/src/runtime/memclr_ppc64x.s
@@ -10,11 +10,22 @@
 TEXT runtime·memclr(SB),NOSPLIT,$0-16
 	MOVD	ptr+0(FP), R3
 	MOVD	n+8(FP), R4
-	CMP	R4, $0
+	SRADCC	$3, R4, R6	// R6 is the number of words to zero
+	BEQ	bytes
+
+	SUB	$8, R3
+	MOVD	R6, CTR
+	MOVDU	R0, 8(R3)
+	BC	25, 0, -1(PC)	// bdnz+ $-4
+	ADD	$8, R3
+
+bytes:
+	ANDCC	$7, R4, R7	// R7 is the number of bytes to zero
 	BEQ	done
 	SUB	$1, R3
-	MOVD	R4, CTR
+	MOVD	R7, CTR
 	MOVBU	R0, 1(R3)
-	BC	25, 0, -1(PC) // bdnz+ $-4
+	BC	25, 0, -1(PC)	// bdnz+ $-4
+
 done:
 	RET
diff --git a/src/runtime/memmove_ppc64x.s b/src/runtime/memmove_ppc64x.s
index 3ada63e633..72c90de379 100644
--- a/src/runtime/memmove_ppc64x.s
+++ b/src/runtime/memmove_ppc64x.s
@@ -16,25 +16,73 @@ TEXT runtime·memmove(SB), NOSPLIT, $-8-24
 	RET
 
 check:
-	CMP	R3, R4
-	BGT	backward
+	ANDCC	$7, R5, R7	// R7 is the number of bytes to copy and CR0[EQ] is set if there are none.
+	SRAD	$3, R5, R6	// R6 is the number of words to copy
+	CMP	R6, $0, CR1	// CR1[EQ] is set if there are no words to copy.
 
+	CMP	R3, R4, CR2
+	BC	12, 9, backward	// I think you should be able to write this as "BGT CR2, backward"
+
+	// Copying forward proceeds by copying R6 words then copying R7 bytes.
+	// R3 and R4 are advanced as we copy. Becuase PPC64 lacks post-increment
+	// load/store, R3 and R4 point before the bytes that are to be copied.
+
+	BC	12, 6, noforwardlarge	// "BEQ CR1, noforwardlarge"
+
+	MOVD	R6, CTR
+
+	SUB	$8, R3
+	SUB	$8, R4
+
+forwardlargeloop:
+	MOVDU	8(R4), R8
+	MOVDU	R8, 8(R3)
+	BC	16, 0, forwardlargeloop // "BDNZ"
+
+	ADD	$8, R3
+	ADD	$8, R4
+
+noforwardlarge:
+	BNE	forwardtail	// Tests the bit set by ANDCC above
+	RET
+
+forwardtail:
 	SUB	$1, R3
-	ADD	R3, R5
 	SUB	$1, R4
-loop:
-	MOVBU	1(R4), R6
-	MOVBU	R6, 1(R3)
-	CMP	R3, R5
-	BNE	loop
+	MOVD	R7, CTR
+
+forwardtailloop:
+	MOVBZU	1(R4), R8
+	MOVBZU	R8, 1(R3)
+	BC	16, 0, forwardtailloop
 	RET
 
 backward:
-	ADD	R5, R4
-	ADD	R3, R5
-loop1:
-	MOVBU	-1(R4), R6
-	MOVBU	R6, -1(R5)
-	CMP	R3, R5
-	BNE	loop1
+	// Copying backwards proceeds by copying R7 bytes then copying R6 words.
+	// R3 and R4 are advanced to the end of the destination/source buffers
+	// respectively and moved back as we copy.
+
+	ADD	R5, R4, R4
+	ADD	R3, R5, R3
+
+	BEQ	nobackwardtail
+
+	MOVD	R7, CTR
+
+backwardtailloop:
+	MOVBZU	-1(R4), R8
+	MOVBZU	R8, -1(R3)
+	BC	16, 0, backwardtailloop
+
+nobackwardtail:
+	BC	4, 6, backwardlarge		// "BNE CR1"
+	RET
+
+backwardlarge:
+	MOVD	R6, CTR
+
+backwardlargeloop:
+	MOVDU	-8(R4), R8
+	MOVDU	R8, -8(R3)
+	BC	16, 0, backwardlargeloop	// "BDNZ"
 	RET