powerpc64: Optimize strcpy and stpcpy for Power9/10

This patch modifies the current Power9 implementation of strcpy and
stpcpy to optimize it for Power9 and Power10.

No new Power10 instructions are used, so the original Power9 strcpy
is modified instead of creating a new implementation for Power10.

The changes also affect stpcpy, which uses the same implementation
with some additional code before returning.

Improvements compared to the old Power9 version:

Use simple comparisons for the first ~512 bytes:
  The main loop is good for long strings, but comparing 16B each time is
  better for shorter strings. After aligning the address to 16 bytes, we
  unroll the loop four times, checking 128 bytes each time. There may be
  some overlap with the main loop for unaligned strings, but it is better
  for shorter strings.

Loop with 64 bytes for longer bytes:
  Use 4 consecutive lxv/stxv instructions.

Showed an average improvement of 13%.

Reviewed-by: Paul E. Murphy <murphyp@linux.ibm.com>
Reviewed-by: Peter Bergner <bergner@linux.ibm.com>

diff --git a/sysdeps/powerpc/powerpc64/le/power9/strcpy.S b/sysdeps/powerpc/powerpc64/le/power9/strcpy.S
index 603bde1e3989d5c28b2693ebb653f5e1d3431d66..2f50625a19929c6602e97926b11fa8b0de29b420 100644 (file)
--- a/sysdeps/powerpc/powerpc64/le/power9/strcpy.S
+++ b/sysdeps/powerpc/powerpc64/le/power9/strcpy.S
@@ -42,22 +42,48 @@
 
    if USE_AS_STPCPY is defined.
 
-   The implementation can load bytes past a null terminator, but only
-   up to the next 16B boundary, so it never crosses a page.  */
+   This implementation never reads across a page boundary, but may
+   read beyond the NUL terminator.  */
 
-/* Load quadword at addr+offset to vreg, check for null bytes,
+/* Load 4 quadwords, merge into one VR for speed and check for NUL
+   and branch to label if NUL is found.  */
+#define CHECK_64B(offset,addr,label)           \
+       lxv     32+v4,(offset+0)(addr);         \
+       lxv     32+v5,(offset+16)(addr);        \
+       lxv     32+v6,(offset+32)(addr);        \
+       lxv     32+v7,(offset+48)(addr);        \
+       vminub  v14,v4,v5;                      \
+       vminub  v15,v6,v7;                      \
+       vminub  v16,v14,v15;                    \
+       vcmpequb.       v0,v16,v18;             \
+       beq     cr6,$+12;                       \
+       li      r7,offset;                      \
+       b       L(label);                       \
+       stxv    32+v4,(offset+0)(r11);          \
+       stxv    32+v5,(offset+16)(r11);         \
+       stxv    32+v6,(offset+32)(r11);         \
+       stxv    32+v7,(offset+48)(r11)
+
+/* Load quadword at addr+offset to vreg, check for NUL bytes,
    and branch to label if any are found.  */
-#define CHECK16(vreg,offset,addr,label) \
-       lxv     vreg+32,offset(addr);   \
-       vcmpequb. v6,vreg,v18;  \
+#define CHECK_16B(vreg,offset,addr,label)      \
+       lxv     vreg+32,offset(addr);           \
+       vcmpequb.       v15,vreg,v18;           \
        bne     cr6,L(label);
 
-.machine power9
+/* Store vreg2 with length if NUL is found.  */
+#define STORE_WITH_LEN(vreg1,vreg2,reg)        \
+       vctzlsbb        r8,vreg1;               \
+       addi    r9,r8,1;                        \
+       sldi    r9,r9,56;                       \
+       stxvl   32+vreg2,reg,r9;
+
+.machine       power9
 ENTRY_TOCLESS (FUNC_NAME, 4)
        CALL_MCOUNT 2
 
-       vspltisb v18,0          /* Zeroes in v18  */
-       vspltisb v19,-1         /* 0xFF bytes in v19  */
+       vspltisb        v18,0           /* Zeroes in v18.  */
+       vspltisb        v19,-1          /* 0xFF bytes in v19.  */
 
        /* Next 16B-aligned address. Prepare address for L(loop).  */
        addi    r5,r4,16
@@ -70,14 +96,11 @@ ENTRY_TOCLESS (FUNC_NAME, 4)
        lvsr    v1,0,r4
        vperm   v0,v19,v0,v1
 
-       vcmpequb. v6,v0,v18     /* 0xff if byte is NULL, 0x00 otherwise  */
+       vcmpequb.       v6,v0,v18       /* 0xff if byte is NUL, 0x00 otherwise.  */
        beq     cr6,L(no_null)
 
-       /* There's a null byte.  */
-       vctzlsbb r8,v6          /* Number of trailing zeroes  */
-       addi    r9,r8,1         /* Add null byte.  */
-       sldi    r10,r9,56       /* stxvl wants size in top 8 bits.  */
-       stxvl   32+v0,r3,r10    /* Partial store  */
+       /* There's a NUL byte.  */
+       STORE_WITH_LEN(v6,v0,r3)
 
 #ifdef USE_AS_STPCPY
        /* stpcpy returns the dest address plus the size not counting the
@@ -87,17 +110,22 @@ ENTRY_TOCLESS (FUNC_NAME, 4)
        blr
 
 L(no_null):
-       sldi    r10,r8,56       /* stxvl wants size in top 8 bits  */
-       stxvl   32+v0,r3,r10    /* Partial store  */
+       sldi    r10,r8,56       /* stxvl wants size in top 8 bits.  */
+       stxvl   32+v0,r3,r10    /* Partial store.  */
 
+/* The main loop is optimized for longer strings(> 512 bytes),
+   so checking the first bytes in 16B chunks benefits shorter
+   strings a lot.  */
        .p2align 4
-L(loop):
-       CHECK16(v0,0,r5,tail1)
-       CHECK16(v1,16,r5,tail2)
-       CHECK16(v2,32,r5,tail3)
-       CHECK16(v3,48,r5,tail4)
-       CHECK16(v4,64,r5,tail5)
-       CHECK16(v5,80,r5,tail6)
+L(aligned):
+       CHECK_16B(v0,0,r5,tail1)
+       CHECK_16B(v1,16,r5,tail2)
+       CHECK_16B(v2,32,r5,tail3)
+       CHECK_16B(v3,48,r5,tail4)
+       CHECK_16B(v4,64,r5,tail5)
+       CHECK_16B(v5,80,r5,tail6)
+       CHECK_16B(v6,96,r5,tail7)
+       CHECK_16B(v7,112,r5,tail8)
 
        stxv    32+v0,0(r11)
        stxv    32+v1,16(r11)
@@ -105,21 +133,146 @@ L(loop):
        stxv    32+v3,48(r11)
        stxv    32+v4,64(r11)
        stxv    32+v5,80(r11)
+       stxv    32+v6,96(r11)
+       stxv    32+v7,112(r11)
 
-       addi    r5,r5,96
-       addi    r11,r11,96
+       addi    r11,r11,128
+
+       CHECK_16B(v0,128,r5,tail1)
+       CHECK_16B(v1,128+16,r5,tail2)
+       CHECK_16B(v2,128+32,r5,tail3)
+       CHECK_16B(v3,128+48,r5,tail4)
+       CHECK_16B(v4,128+64,r5,tail5)
+       CHECK_16B(v5,128+80,r5,tail6)
+       CHECK_16B(v6,128+96,r5,tail7)
+       CHECK_16B(v7,128+112,r5,tail8)
+
+       stxv    32+v0,0(r11)
+       stxv    32+v1,16(r11)
+       stxv    32+v2,32(r11)
+       stxv    32+v3,48(r11)
+       stxv    32+v4,64(r11)
+       stxv    32+v5,80(r11)
+       stxv    32+v6,96(r11)
+       stxv    32+v7,112(r11)
+
+       addi    r11,r11,128
+
+       CHECK_16B(v0,256,r5,tail1)
+       CHECK_16B(v1,256+16,r5,tail2)
+       CHECK_16B(v2,256+32,r5,tail3)
+       CHECK_16B(v3,256+48,r5,tail4)
+       CHECK_16B(v4,256+64,r5,tail5)
+       CHECK_16B(v5,256+80,r5,tail6)
+       CHECK_16B(v6,256+96,r5,tail7)
+       CHECK_16B(v7,256+112,r5,tail8)
+
+       stxv    32+v0,0(r11)
+       stxv    32+v1,16(r11)
+       stxv    32+v2,32(r11)
+       stxv    32+v3,48(r11)
+       stxv    32+v4,64(r11)
+       stxv    32+v5,80(r11)
+       stxv    32+v6,96(r11)
+       stxv    32+v7,112(r11)
+
+       addi    r11,r11,128
+
+       CHECK_16B(v0,384,r5,tail1)
+       CHECK_16B(v1,384+16,r5,tail2)
+       CHECK_16B(v2,384+32,r5,tail3)
+       CHECK_16B(v3,384+48,r5,tail4)
+       CHECK_16B(v4,384+64,r5,tail5)
+       CHECK_16B(v5,384+80,r5,tail6)
+       CHECK_16B(v6,384+96,r5,tail7)
+       CHECK_16B(v7,384+112,r5,tail8)
+
+       stxv    32+v0,0(r11)
+       stxv    32+v1,16(r11)
+       stxv    32+v2,32(r11)
+       stxv    32+v3,48(r11)
+       stxv    32+v4,64(r11)
+       stxv    32+v5,80(r11)
+       stxv    32+v6,96(r11)
+       stxv    32+v7,112(r11)
+
+       /* Align src pointer down to a 64B boundary.  */
+       addi    r5,r4,512
+       clrrdi  r5,r5,6
+       subf    r7,r4,r5
+       add     r11,r3,r7
+
+/* Switch to a more aggressive approach checking 64B each time.  */
+       .p2align 5
+L(strcpy_loop):
+       CHECK_64B(0,r5,tail_64b)
+       CHECK_64B(64,r5,tail_64b)
+       CHECK_64B(128,r5,tail_64b)
+       CHECK_64B(192,r5,tail_64b)
+
+       CHECK_64B(256,r5,tail_64b)
+       CHECK_64B(256+64,r5,tail_64b)
+       CHECK_64B(256+128,r5,tail_64b)
+       CHECK_64B(256+192,r5,tail_64b)
+       addi    r5,r5,512
+       addi    r11,r11,512
+
+       b       L(strcpy_loop)
+
+       .p2align 5
+L(tail_64b):
+       /* OK, we found a NUL byte.  Let's look for it in the current 64-byte
+          block and mark it in its corresponding VR.  */
+       add     r11,r11,r7
+       vcmpequb.       v8,v4,v18
+       beq     cr6,L(no_null_16B)
+       /* There's a NUL byte.  */
+       STORE_WITH_LEN(v8,v4,r11)
+#ifdef USE_AS_STPCPY
+       add     r3,r11,r8
+#endif
+       blr
+
+L(no_null_16B):
+       stxv    32+v4,0(r11)
+       vcmpequb.       v8,v5,v18
+       beq     cr6,L(no_null_32B)
+       /* There's a NUL byte.  */
+       addi    r11,r11,16
+       STORE_WITH_LEN(v8,v5,r11)
+#ifdef USE_AS_STPCPY
+       add     r3,r11,r8
+#endif
+       blr
 
-       b       L(loop)
+L(no_null_32B):
+       stxv    32+v5,16(r11)
+       vcmpequb.       v8,v6,v18
+       beq     cr6,L(no_null_48B)
+       /* There's a NUL byte.  */
+       addi    r11,r11,32
+       STORE_WITH_LEN(v8,v6,r11)
+#ifdef USE_AS_STPCPY
+       add     r3,r11,r8
+#endif
+       blr
+
+L(no_null_48B):
+       stxv    32+v6,32(r11)
+       vcmpequb.       v8,v7,v18;
+       /* There's a NUL byte.  */
+       addi    r11,r11,48
+       STORE_WITH_LEN(v8,v7,r11)
+#ifdef USE_AS_STPCPY
+       add     r3,r11,r8
+#endif
+       blr
 
        .p2align 4
 L(tail1):
-       vctzlsbb r8,v6          /* Number of trailing zeroes  */
-       addi    r9,r8,1         /* Add null terminator  */
-       sldi    r9,r9,56        /* stxvl wants size in top 8 bits  */
-       stxvl   32+v0,r11,r9    /* Partial store  */
+       /* There's a NUL byte.  */
+       STORE_WITH_LEN(v15,v0,r11)
 #ifdef USE_AS_STPCPY
-       /* stpcpy returns the dest address plus the size not counting the
-          final '\0'.  */
        add     r3,r11,r8
 #endif
        blr
@@ -127,11 +280,9 @@ L(tail1):
        .p2align 4
 L(tail2):
        stxv    32+v0,0(r11)
-       vctzlsbb r8,v6
-       addi    r9,r8,1
-       sldi    r9,r9,56
+       /* There's a NUL byte.  */
        addi    r11,r11,16
-       stxvl   32+v1,r11,r9
+       STORE_WITH_LEN(v15,v1,r11)
 #ifdef USE_AS_STPCPY
        add     r3,r11,r8
 #endif
@@ -141,11 +292,8 @@ L(tail2):
 L(tail3):
        stxv    32+v0,0(r11)
        stxv    32+v1,16(r11)
-       vctzlsbb r8,v6
-       addi    r9,r8,1
-       sldi    r9,r9,56
        addi    r11,r11,32
-       stxvl   32+v2,r11,r9
+       STORE_WITH_LEN(v15,v2,r11)
 #ifdef USE_AS_STPCPY
        add     r3,r11,r8
 #endif
@@ -156,11 +304,8 @@ L(tail4):
        stxv    32+v0,0(r11)
        stxv    32+v1,16(r11)
        stxv    32+v2,32(r11)
-       vctzlsbb r8,v6
-       addi    r9,r8,1
-       sldi    r9,r9,56
        addi    r11,r11,48
-       stxvl   32+v3,r11,r9
+       STORE_WITH_LEN(v15,v3,r11)
 #ifdef USE_AS_STPCPY
        add     r3,r11,r8
 #endif
@@ -172,11 +317,8 @@ L(tail5):
        stxv    32+v1,16(r11)
        stxv    32+v2,32(r11)
        stxv    32+v3,48(r11)
-       vctzlsbb r8,v6
-       addi    r9,r8,1
-       sldi    r9,r9,56
        addi    r11,r11,64
-       stxvl   32+v4,r11,r9
+       STORE_WITH_LEN(v15,v4,r11)
 #ifdef USE_AS_STPCPY
        add     r3,r11,r8
 #endif
@@ -189,11 +331,39 @@ L(tail6):
        stxv    32+v2,32(r11)
        stxv    32+v3,48(r11)
        stxv    32+v4,64(r11)
-       vctzlsbb r8,v6
-       addi    r9,r8,1
-       sldi    r9,r9,56
        addi    r11,r11,80
-       stxvl   32+v5,r11,r9
+       STORE_WITH_LEN(v15,v5,r11)
+#ifdef USE_AS_STPCPY
+       add     r3,r11,r8
+#endif
+       blr
+
+       .p2align 4
+L(tail7):
+       stxv    32+v0,0(r11)
+       stxv    32+v1,16(r11)
+       stxv    32+v2,32(r11)
+       stxv    32+v3,48(r11)
+       stxv    32+v4,64(r11)
+       stxv    32+v5,80(r11)
+       addi    r11,r11,96
+       STORE_WITH_LEN(v15,v6,r11)
+#ifdef USE_AS_STPCPY
+       add     r3,r11,r8
+#endif
+       blr
+
+       .p2align 4
+L(tail8):
+       stxv    32+v0,0(r11)
+       stxv    32+v1,16(r11)
+       stxv    32+v2,32(r11)
+       stxv    32+v3,48(r11)
+       stxv    32+v4,64(r11)
+       stxv    32+v5,80(r11)
+       stxv    32+v6,96(r11)
+       addi    r11,r11,112
+       STORE_WITH_LEN(v15,v7,r11)
 #ifdef USE_AS_STPCPY
        add     r3,r11,r8
 #endif