diff options
Diffstat (limited to 'sysdeps/powerpc')
| -rw-r--r-- | sysdeps/powerpc/powerpc64/memcpy.S | 327 |
1 files changed, 241 insertions, 86 deletions
diff --git a/sysdeps/powerpc/powerpc64/memcpy.S b/sysdeps/powerpc/powerpc64/memcpy.S index f3448e0b31..251e1fed80 100644 --- a/sysdeps/powerpc/powerpc64/memcpy.S +++ b/sysdeps/powerpc/powerpc64/memcpy.S @@ -24,12 +24,12 @@ /* __ptr_t [r3] memcpy (__ptr_t dst [r3], __ptr_t src [r4], size_t len [r5]); Returns 'dst'. - Memcpy handles short copies (< 32-bytes) using an unaligned - word lwz/stw loop. The tail (remaining 1-3) bytes is handled with the - appropriate combination of byte and halfword load/stores. There is no - attempt to optimize the alignment of short moves. The 64-bit - implementations of POWER3 and POWER4 do a reasonable job of handling - unligned load/stores that do not cross 32-byte boundries. + Memcpy handles short copies (< 32-bytes) using a binary move blocks + (no loops) of lwz/stw. The tail (remaining 1-3) bytes is handled + with the appropriate combination of byte and halfword load/stores. + There is minimal effort to optimize the alignment of short moves. + The 64-bit implementations of POWER3 and POWER4 do a reasonable job + of handling unligned load/stores that do not cross 32-byte boundries. Longer moves (>= 32-bytes) justify the effort to get at least the destination doubleword (8-byte) aligned. Further optimization is @@ -39,18 +39,22 @@ EALIGN (BP_SYM (memcpy), 5, 0) cmpldi cr1,5,31 neg 0,3 - std 30,-16(1) + std 3,-16(1) std 31,-8(1) - rldicl. 0,0,0,61 + andi. 11,3,7 /* check alignement of dst. */ + clrldi 0,0,61 /* Number of bytes until the 1st doubleword of dst. */ + clrldi 10,4,61 /* check alignement of src. */ + cmpldi cr6,5,8 + ble- cr1,.L2 /* If move < 32 bytes use short move code. */ + cmpld cr6,10,11 mr 12,4 + srdi 9,5,3 /* Number of full double words remaining. */ + mtcrf 0x01,0 mr 31,5 - mr 30,3 - ble- cr1,.L2 + beq .L0 + subf 31,0,5 - /* Move 0-7 bytes as needed to get the destination doubleword alligned. */ - beq 0f - mtcrf 0x01,0 1: bf 31,2f lbz 6,0(12) addi 12,12,1 @@ -67,88 +71,91 @@ EALIGN (BP_SYM (memcpy), 5, 0) stw 6,0(3) addi 3,3,4 0: + clrldi 10,12,61 /* check alignement of src again. */ + srdi 9,31,3 /* Number of full double words remaining. */ + /* Copy doublewords from source to destination, assumpting the destination is aligned on a doubleword boundary. - First verify that there is > 7 bytes to copy and check if the source - is also doubleword aligned. If there are < 8 bytes to copy fall - through to the tail byte copy code. Otherwise if the source and - destination are both doubleword aligned use an optimized doubleword - copy loop. Otherwise the source has a different alignment and we use - a load, shift, store strategy. */ - rldicl. 0,12,0,61 - cmpldi cr6,31,7 - ble- cr6,.L2 /* less than 8 bytes left. */ - srdi 11,31,3 - andi. 10,12,7 - bne- 0,.L6 /* Source is not DW aligned. */ - srdi. 9,31,3 - mr 10,3 - mr 11,12 + At this point we know there are at least 25 bytes left (32-7) to copy. + The next step is to determine if the source is also doubleword aligned. + If not branch to the unaligned move code at .L6. which uses + a load, shift, store strategy. + + Otherwise source and destination are doubleword aligned, and we can + the optimized doubleword copy loop. */ +.L0: + clrldi 11,31,61 + mtcrf 0x01,9 + bne- cr6,.L6 /* If source is not DW aligned. */ - /* Move doublewords where destination and source are aligned. + /* Move doublewords where destination and source are DW aligned. Use a unrolled loop to copy 4 doubleword (32-bytes) per iteration. - If the remainder is >0 and < 32 bytes copy 1-3 doublewords. */ + If the the copy is not an exact multiple of 32 bytes, 1-3 + doublewords are copied as needed to set up the main loop. After + the main loop exits there may be a tail of 1-7 bytes. These byte are + copied a word/halfword/byte at a time as needed to preserve alignment. */ + + srdi 8,31,5 cmpldi cr1,9,4 - beq 0f - mtcrf 0x01,9 - blt cr1,2f - ld 6,0(11) + cmpldi cr6,11,0 + mr 11,12 + + bf 30,1f + ld 6,0(12) + ld 7,8(12) + addi 11,12,16 + mtctr 8 + std 6,0(3) + std 7,8(3) + addi 10,3,16 + bf 31,4f + ld 0,16(12) + std 0,16(3) + blt cr1,3f + addi 11,12,24 + addi 10,3,24 + b 4f + .align 4 +1: + mr 10,3 + mtctr 8 + bf 31,4f + ld 6,0(12) + addi 11,12,8 + std 6,0(3) + addi 10,3,8 + .align 4 4: - ld 7,8(11) - addi 9,9,-4 - std 6,0(10) - ld 6,16(11) - std 7,8(10) - ld 7,24(11) - addi 11,11,32 - cmpldi cr1,9,4 - std 6,16(10) - blt cr1,3f - ld 6,0(11) - std 7,24(10) - addi 10,10,32 - b 4b -3: std 7,24(10) - addi 10,10,32 -2: bf 30,1f ld 6,0(11) ld 7,8(11) - addi 11,11,16 + ld 8,16(11) + ld 0,24(11) + addi 11,11,32 +2: std 6,0(10) std 7,8(10) - addi 10,10,16 -1: bf 31,0f - ld 6,0(11) - addi 11,11,8 - std 6,0(10) - addi 10,10,8 -0: + std 8,16(10) + std 0,24(10) + addi 10,10,32 + bdnz 4b +3: -.L8: rldicr 0,31,0,60 - rldicl 31,31,0,61 + mtcrf 0x01,31 + beq cr6,0f +.L9: add 3,3,0 add 12,12,0 - - /* Copy the tail for up to 31 bytes. If this is the tail of a longer - copy then the destination will be aligned and the length will be - less than 8. So it is normally not worth the set-up overhead to - get doubleword aligned and do doubleword load/store. */ -.L2: - mr. 10,31 - cmpldi cr1,31,4 - beq 0f - mtcrf 0x01,31 - blt cr1,2f -4: lwz 6,0(12) + +/* At this point we have a tail of 0-7 bytes and we know that the + destiniation is double word aligned. */ +4: bf 29,2f + lwz 6,0(12) addi 12,12,4 - addi 10,10,-4 stw 6,0(3) - cmpldi cr1,10,4 addi 3,3,4 - bge cr1,4b 2: bf 30,1f lhz 6,0(12) addi 12,12,2 @@ -156,14 +163,153 @@ EALIGN (BP_SYM (memcpy), 5, 0) addi 3,3,2 1: bf 31,0f lbz 6,0(12) - addi 12,12,1 stb 6,0(3) - addi 3,3,1 0: /* Return original dst pointer. */ ld 31,-8(1) - mr 3,30 - ld 30,-16(1) + ld 3,-16(1) + blr + +/* Copy up to 31 bytes. This divided into two cases 0-8 bytes and 9-31 + bytes. Each case is handled without loops, using binary (1,2,4,8) + tests. + + In the short (0-8 byte) case no attempt is made to force alignment + of either source or destination. The hardware will handle the + unaligned load/stores with small delays for crossing 32- 64-byte, and + 4096-byte boundaries. Since these short moves are unlikely to be + unaligned or cross these boundaries, the overhead to force + alignment is not justified. + + The longer (9-31 byte) move is more likely to cross 32- or 64-byte + boundaries. Since only loads are sensitive to the 32-/64-byte + boundaries it is more important to align the source then the + destination. If the source is not already word aligned, we first + move 1-3 bytes as needed. Since we are only word aligned we don't + use double word load/stores to insure that all loads are aligned. + While the destination and stores may still be unaligned, this + is only an issue for page (4096 byte boundary) crossing, which + should be rare for these short moves. The hardware handles this + case automatically with a small delay. */ + + .align 4 +.L2: + mtcrf 0x01,5 + neg 8,4 + clrrdi 11,4,2 + andi. 0,8,3 + ble cr6,.LE8 /* Handle moves of 0-8 bytes. */ +/* At least 9 bytes left. Get the source word aligned. */ + cmpldi cr1,5,16 + mr 10,5 + mr 12,4 + cmpldi cr6,0,2 + beq .L3 /* If the source is already word aligned skip this. */ +/* Copy 1-3 bytes to get source address word aligned. */ + lwz 6,0(11) + subf 10,0,5 + add 12,4,0 + blt cr6,5f + srdi 7,6,16 + bgt cr6,3f + sth 6,0(3) + b 7f + .align 4 +3: + stb 7,0(3) + sth 6,1(3) + b 7f + .align 4 +5: + stb 6,0(3) +7: + cmpldi cr1,10,16 + add 3,3,0 + mtcrf 0x01,10 + .align 4 +.L3: +/* At least 6 bytes left and the source is word aligned. */ + blt cr1,8f +16: /* Move 16 bytes. */ + lwz 6,0(12) + lwz 7,4(12) + stw 6,0(3) + lwz 6,8(12) + stw 7,4(3) + lwz 7,12(12) + addi 12,12,16 + stw 6,8(3) + stw 7,12(3) + addi 3,3,16 +8: /* Move 8 bytes. */ + bf 28,4f + lwz 6,0(12) + lwz 7,4(12) + addi 12,12,8 + stw 6,0(3) + stw 7,4(3) + addi 3,3,8 +4: /* Move 4 bytes. */ + bf 29,2f + lwz 6,0(12) + addi 12,12,4 + stw 6,0(3) + addi 3,3,4 +2: /* Move 2-3 bytes. */ + bf 30,1f + lhz 6,0(12) + sth 6,0(3) + bf 31,0f + lbz 7,2(12) + stb 7,2(3) + ld 3,-16(1) + blr +1: /* Move 1 byte. */ + bf 31,0f + lbz 6,0(12) + stb 6,0(3) +0: + /* Return original dst pointer. */ + ld 3,-16(1) + blr + +/* Special case to copy 0-8 bytes. */ + .align 4 +.LE8: + mr 12,4 + bne cr6,4f +/* Would have liked to use use ld/std here but the 630 processors are + slow for load/store doubles that are not at least word aligned. + Unaligned Load/Store word execute with only a 1 cycle penaltity. */ + lwz 6,0(4) + lwz 7,4(4) + stw 6,0(3) + stw 7,4(3) + /* Return original dst pointer. */ + ld 3,-16(1) + blr + .align 4 +4: bf 29,2b + lwz 6,0(4) + stw 6,0(3) +6: + bf 30,5f + lhz 7,4(4) + sth 7,4(3) + bf 31,0f + lbz 8,6(4) + stb 8,6(3) + ld 3,-16(1) + blr + .align 4 +5: + bf 31,0f + lbz 6,4(4) + stb 6,4(3) + .align 4 +0: + /* Return original dst pointer. */ + ld 3,-16(1) blr .align 4 @@ -173,27 +319,29 @@ EALIGN (BP_SYM (memcpy), 5, 0) not. Use aligned doubleword loads from the source, shifted to realign the data, to allow aligned destination stores. */ subf 5,10,12 - andi. 0,11,1 + andi. 0,9,1 + cmpldi cr6,11,0 sldi 10,10,3 + mr 11,9 mr 4,3 ld 6,0(5) ld 7,8(5) subfic 9,10,64 beq 2f sld 0,6,10 - addi 11,11,-1 + cmpldi 11,1 mr 6,7 addi 4,4,-8 - cmpldi 11,0 + addi 11,11,-1 b 1f 2: addi 5,5,8 .align 4 0: sld 0,6,10 srd 8,7,9 - addi 11,11,-2 + cmpldi 11,2 ld 6,8(5) or 0,0,8 - cmpldi 11,0 + addi 11,11,-2 std 0,0(4) sld 0,7,10 1: srd 8,6,9 @@ -204,8 +352,15 @@ EALIGN (BP_SYM (memcpy), 5, 0) addi 5,5,16 addi 4,4,16 b 0b + .align 4 8: std 0,8(4) - b .L8 + rldicr 0,31,0,60 + mtcrf 0x01,31 + bne cr6,.L9 /* If the tail is 0 bytes we are done! */ + /* Return original dst pointer. */ + ld 31,-8(1) + ld 3,-16(1) + blr END_GEN_TB (BP_SYM (memcpy),TB_TOCLESS) libc_hidden_builtin_def (memcpy) |