math/big: add PCALIGN to addMulVVW asm on ppc64x

Adding PCALIGN to addMulVVW assembler implementation
provides the following improvement on power10:

    AddMulVVW/1         3.36ns ± 0%    3.37ns ± 0%   +0.20%
    AddMulVVW/2         4.45ns ± 0%    4.44ns ± 0%   -0.25%
    AddMulVVW/3         5.44ns ± 0%    5.49ns ± 0%   +0.84%
    AddMulVVW/4         6.43ns ± 0%    6.34ns ± 0%   -1.33%
    AddMulVVW/5         7.87ns ± 0%    7.73ns ± 0%   -1.70%
    AddMulVVW/10        13.4ns ± 3%    12.4ns ± 7%   -7.07%
    AddMulVVW/100        112ns ± 0%     102ns ± 0%   -9.34%
    AddMulVVW/1000      1.09µs ± 0%    0.95µs ± 0%  -13.15%
    AddMulVVW/10000     10.9µs ± 0%     9.6µs ± 0%  -12.46%
    AddMulVVW/100000     109µs ± 0%      95µs ± 0%  -12.58%

Change-Id: Ic33d4f125c84d568f63e17cf99dc4df5ca9328d9
Reviewed-on: https://go-review.googlesource.com/c/go/+/447236
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Bryan Mills <bcmills@google.com>
Reviewed-by: Russ Cox <rsc@golang.org>
Run-TryBot: Lynn Boger <laboger@linux.vnet.ibm.com>
Reviewed-by: Paul Murphy <murp@ibm.com>
Reviewed-by: Archana Ravindar <ravindararchana@gmail.com>

diff --git a/src/math/big/arith_ppc64x.s b/src/math/big/arith_ppc64x.s
index a83696a0cbf3702264a7d615bf32615acb9bd96e..5fdbf40a24969256688df0546ba285fc1fb9f395 100644 (file)
--- a/src/math/big/arith_ppc64x.s
+++ b/src/math/big/arith_ppc64x.s
@@ -44,6 +44,8 @@ TEXT ·addVV(SB), NOSPLIT, $0
        // for small values of z_len (0.90x in the worst case), but
        // gain significant performance as z_len increases (up to
        // 1.45x).
+
+       PCALIGN $32
 loop:
        MOVD  8(R8), R11      // R11 = x[i]
        MOVD  16(R8), R12     // R12 = x[i+1]
@@ -131,6 +133,8 @@ TEXT ·subVV(SB), NOSPLIT, $0
        // for small values of z_len (0.92x in the worst case), but
        // gain significant performance as z_len increases (up to
        // 1.45x).
+
+       PCALIGN $32
 loop:
        MOVD  8(R8), R11      // R11 = x[i]
        MOVD  16(R8), R12     // R12 = x[i+1]
@@ -212,6 +216,7 @@ TEXT ·addVW(SB), NOSPLIT, $0
        CMP   R0, R9
        MOVD  R9, CTR           // Set up the loop counter
        BEQ   tail              // If R9 = 0, we can't use the loop
+       PCALIGN $32
 
 loop:
        MOVD  8(R8), R20        // R20 = x[i]
@@ -288,6 +293,8 @@ TEXT ·subVW(SB), NOSPLIT, $0
        // The loop here is almost the same as the one used in s390x, but
        // we don't need to capture CA every iteration because we've already
        // done that above.
+
+       PCALIGN $32
 loop:
        MOVD  8(R8), R20
        MOVD  16(R8), R21
@@ -358,6 +365,7 @@ TEXT ·shlVU(SB), NOSPLIT, $0
        CMP     R5, R0          // iterate from i=len(z)-1 to 0
        BEQ     loopexit        // Already at end?
        MOVD    0(R15),R10      // x[i]
+       PCALIGN $32
 shloop:
        SLD     R9, R10, R10    // x[i]<<s
        MOVDU   -8(R15), R14
@@ -520,6 +528,7 @@ TEXT ·mulAddVWW(SB), NOSPLIT, $0
        CMP     R0, R14
        MOVD    R14, CTR          // Set up the loop counter
        BEQ     tail              // If R9 = 0, we can't use the loop
+       PCALIGN $32
 
 loop:
        MOVD    8(R8), R20        // R20 = x[i]
@@ -602,6 +611,7 @@ TEXT ·addMulVVW(SB), NOSPLIT, $0
        MOVD R0, R4             // R4 = c = 0
        MOVD R22, CTR           // Initialize loop counter
        BEQ  done
+       PCALIGN $32
 
 loop:
        MOVD  (R8)(R3), R20     // Load x[i]