[PATCH v3 2/3] riscv: memcpy_noalignment: Fold SZREG/BLOCK_SIZE alignment to single andi

[Yao Zihong]

Simplify the alignment steps for SZREG and BLOCK_SIZE multiples. The previous
three-instruction sequences

    addi    a7, a2, -SZREG
    andi    a7, a7, -SZREG
    addi    a7, a7, SZREG

and

    addi    a7, a2, -BLOCK_SIZE
    andi    a7, a7, -BLOCK_SIZE
    addi    a7, a7, BLOCK_SIZE

are equivalent to a single

    andi    a7, a2, -SZREG
    andi    a7, a2, -BLOCK_SIZE

because SZREG and BLOCK_SIZE are powers of two in this context, making the
surrounding addi steps cancel out. Folding to one instruction reduces code
size with identical semantics.

No functional change.

sysdeps/riscv/multiarch/memcpy_noalignment.S: Remove redundant addi around
alignment; keep a single andi for SZREG/BLOCK_SIZE rounding.

Signed-off-by: Yao Zihong <zihong.plct@isrc.iscas.ac.cn>
---
 sysdeps/riscv/multiarch/memcpy_noalignment.S | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/sysdeps/riscv/multiarch/memcpy_noalignment.S b/sysdeps/riscv/multiarch/memcpy_noalignment.S
index db8654fb59..6917fc435b 100644
--- a/sysdeps/riscv/multiarch/memcpy_noalignment.S
+++ b/sysdeps/riscv/multiarch/memcpy_noalignment.S
@@ -57,9 +57,7 @@ ENTRY (__memcpy_noalignment)
 	add	a5, a0, a4
 	add	a1, a1, a4
 	bleu	a2, a3, L(word_copy_adjust)
-	addi	a7, a2, -BLOCK_SIZE
-	andi	a7, a7, -BLOCK_SIZE
-	addi	a7, a7, BLOCK_SIZE
+	andi	a7, a2, -BLOCK_SIZE
 	add	a3, a5, a7
 	mv	a4, a1
 L(block_copy):
@@ -106,9 +104,7 @@ L(word_copy):
 	li	a5, SZREG-1
 	/* if LEN < SZREG jump to tail handling.  */
 	bleu	a2, a5, L(tail_adjust)
-	addi	a7, a2, -SZREG
-	andi	a7, a7, -SZREG
-	addi	a7, a7, SZREG
+	andi	a7, a2, -SZREG
 	add	a6, a3, a7
 	mv	a5, a1
 L(word_copy_loop):
-- 
2.47.2