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Date: Wed, 7 Jun 2023 18:07:10 +0800
From: zhangfei <zhang_fei_0403@....com>
To: dalias@...c.org,
musl@...ts.openwall.com
Cc: zhangfei <zhangfei@...iscas.ac.cn>
Subject: [PATCH 3/3] RISC-V: Optimize memmove
From: zhangfei <zhangfei@...iscas.ac.cn>
This code is based on linux/arch/riscv/lib/memcpy.S. Removed macro definition to support
RISCV64.
Signed-off-by: Zhang Fei<zhangfei@...iscas.ac.cn>
---
src/string/riscv64/memmove.S | 315 +++++++++++++++++++++++++++++++++++
1 file changed, 315 insertions(+)
create mode 100644 src/string/riscv64/memmove.S
diff --git a/src/string/riscv64/memmove.S b/src/string/riscv64/memmove.S
new file mode 100644
index 0000000..41b84e3
--- /dev/null
+++ b/src/string/riscv64/memmove.S
@@ -0,0 +1,315 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2022 Michael T. Kloos <michael@...haelkloos.com>
+ */
+
+#define SZREG 8
+#define REG_S sd
+#define REG_L ld
+
+.global memmove
+.type memmove,@function
+memmove:
+ /*
+ * Returns
+ * a0 - dest
+ *
+ * Parameters
+ * a0 - Inclusive first byte of dest
+ * a1 - Inclusive first byte of src
+ * a2 - Length of copy n
+ *
+ * Because the return matches the parameter register a0,
+ * we will not clobber or modify that register.
+ *
+ * Note: This currently only works on little-endian.
+ * To port to big-endian, reverse the direction of shifts
+ * in the 2 misaligned fixup copy loops.
+ */
+
+ /* Return if nothing to do */
+ beq a0, a1, return_from_memmove
+ beqz a2, return_from_memmove
+
+ /*
+ * Register Uses
+ * Forward Copy: a1 - Index counter of src
+ * Reverse Copy: a4 - Index counter of src
+ * Forward Copy: t3 - Index counter of dest
+ * Reverse Copy: t4 - Index counter of dest
+ * Both Copy Modes: t5 - Inclusive first multibyte/aligned of dest
+ * Both Copy Modes: t6 - Non-Inclusive last multibyte/aligned of dest
+ * Both Copy Modes: t0 - Link / Temporary for load-store
+ * Both Copy Modes: t1 - Temporary for load-store
+ * Both Copy Modes: t2 - Temporary for load-store
+ * Both Copy Modes: a5 - dest to src alignment offset
+ * Both Copy Modes: a6 - Shift ammount
+ * Both Copy Modes: a7 - Inverse Shift ammount
+ * Both Copy Modes: a2 - Alternate breakpoint for unrolled loops
+ */
+
+ /*
+ * Solve for some register values now.
+ * Byte copy does not need t5 or t6.
+ */
+ mv t3, a0
+ add t4, a0, a2
+ add a4, a1, a2
+
+ /*
+ * Byte copy if copying less than (2 * SZREG) bytes. This can
+ * cause problems with the bulk copy implementation and is
+ * small enough not to bother.
+ */
+ andi t0, a2, -(2 * SZREG)
+ beqz t0, byte_copy
+
+ /*
+ * Now solve for t5 and t6.
+ */
+ andi t5, t3, -SZREG
+ andi t6, t4, -SZREG
+ /*
+ * If dest(Register t3) rounded down to the nearest naturally
+ * aligned SZREG address, does not equal dest, then add SZREG
+ * to find the low-bound of SZREG alignment in the dest memory
+ * region. Note that this could overshoot the dest memory
+ * region if n is less than SZREG. This is one reason why
+ * we always byte copy if n is less than SZREG.
+ * Otherwise, dest is already naturally aligned to SZREG.
+ */
+ beq t5, t3, 1f
+ addi t5, t5, SZREG
+ 1:
+
+ /*
+ * If the dest and src are co-aligned to SZREG, then there is
+ * no need for the full rigmarole of a full misaligned fixup copy.
+ * Instead, do a simpler co-aligned copy.
+ */
+ xor t0, a0, a1
+ andi t1, t0, (SZREG - 1)
+ beqz t1, coaligned_copy
+ /* Fall through to misaligned fixup copy */
+
+misaligned_fixup_copy:
+ bltu a1, a0, misaligned_fixup_copy_reverse
+
+misaligned_fixup_copy_forward:
+ jal t0, byte_copy_until_aligned_forward
+
+ andi a5, a1, (SZREG - 1) /* Find the alignment offset of src (a1) */
+ slli a6, a5, 3 /* Multiply by 8 to convert that to bits to shift */
+ sub a5, a1, t3 /* Find the difference between src and dest */
+ andi a1, a1, -SZREG /* Align the src pointer */
+ addi a2, t6, SZREG /* The other breakpoint for the unrolled loop*/
+
+ /*
+ * Compute The Inverse Shift
+ * a7 = XLEN - a6 = XLEN + -a6
+ * 2s complement negation to find the negative: -a6 = ~a6 + 1
+ * Add that to XLEN. XLEN = SZREG * 8.
+ */
+ not a7, a6
+ addi a7, a7, (SZREG * 8 + 1)
+
+ /*
+ * Fix Misalignment Copy Loop - Forward
+ * load_val0 = load_ptr[0];
+ * do {
+ * load_val1 = load_ptr[1];
+ * store_ptr += 2;
+ * store_ptr[0 - 2] = (load_val0 >> {a6}) | (load_val1 << {a7});
+ *
+ * if (store_ptr == {a2})
+ * break;
+ *
+ * load_val0 = load_ptr[2];
+ * load_ptr += 2;
+ * store_ptr[1 - 2] = (load_val1 >> {a6}) | (load_val0 << {a7});
+ *
+ * } while (store_ptr != store_ptr_end);
+ * store_ptr = store_ptr_end;
+ */
+
+ REG_L t0, (0 * SZREG)(a1)
+ 1:
+ REG_L t1, (1 * SZREG)(a1)
+ addi t3, t3, (2 * SZREG)
+ srl t0, t0, a6
+ sll t2, t1, a7
+ or t2, t0, t2
+ REG_S t2, ((0 * SZREG) - (2 * SZREG))(t3)
+
+ beq t3, a2, 2f
+
+ REG_L t0, (2 * SZREG)(a1)
+ addi a1, a1, (2 * SZREG)
+ srl t1, t1, a6
+ sll t2, t0, a7
+ or t2, t1, t2
+ REG_S t2, ((1 * SZREG) - (2 * SZREG))(t3)
+
+ bne t3, t6, 1b
+ 2:
+ mv t3, t6 /* Fix the dest pointer in case the loop was broken */
+
+ add a1, t3, a5 /* Restore the src pointer */
+ j byte_copy_forward /* Copy any remaining bytes */
+
+misaligned_fixup_copy_reverse:
+ jal t0, byte_copy_until_aligned_reverse
+
+ andi a5, a4, (SZREG - 1) /* Find the alignment offset of src (a4) */
+ slli a6, a5, 3 /* Multiply by 8 to convert that to bits to shift */
+ sub a5, a4, t4 /* Find the difference between src and dest */
+ andi a4, a4, -SZREG /* Align the src pointer */
+ addi a2, t5, -SZREG /* The other breakpoint for the unrolled loop*/
+
+ /*
+ * Compute The Inverse Shift
+ * a7 = XLEN - a6 = XLEN + -a6
+ * 2s complement negation to find the negative: -a6 = ~a6 + 1
+ * Add that to XLEN. XLEN = SZREG * 8.
+ */
+ not a7, a6
+ addi a7, a7, (SZREG * 8 + 1)
+
+ /*
+ * Fix Misalignment Copy Loop - Reverse
+ * load_val1 = load_ptr[0];
+ * do {
+ * load_val0 = load_ptr[-1];
+ * store_ptr -= 2;
+ * store_ptr[1] = (load_val0 >> {a6}) | (load_val1 << {a7});
+ *
+ * if (store_ptr == {a2})
+ * break;
+ *
+ * load_val1 = load_ptr[-2];
+ * load_ptr -= 2;
+ * store_ptr[0] = (load_val1 >> {a6}) | (load_val0 << {a7});
+ *
+ * } while (store_ptr != store_ptr_end);
+ * store_ptr = store_ptr_end;
+ */
+
+ REG_L t1, ( 0 * SZREG)(a4)
+ 1:
+ REG_L t0, (-1 * SZREG)(a4)
+ addi t4, t4, (-2 * SZREG)
+ sll t1, t1, a7
+ srl t2, t0, a6
+ or t2, t1, t2
+ REG_S t2, ( 1 * SZREG)(t4)
+
+ beq t4, a2, 2f
+
+ REG_L t1, (-2 * SZREG)(a4)
+ addi a4, a4, (-2 * SZREG)
+ sll t0, t0, a7
+ srl t2, t1, a6
+ or t2, t0, t2
+ REG_S t2, ( 0 * SZREG)(t4)
+
+ bne t4, t5, 1b
+ 2:
+ mv t4, t5 /* Fix the dest pointer in case the loop was broken */
+
+ add a4, t4, a5 /* Restore the src pointer */
+ j byte_copy_reverse /* Copy any remaining bytes */
+
+/*
+ * Simple copy loops for SZREG co-aligned memory locations.
+ * These also make calls to do byte copies for any unaligned
+ * data at their terminations.
+ */
+coaligned_copy:
+ bltu a1, a0, coaligned_copy_reverse
+
+coaligned_copy_forward:
+ jal t0, byte_copy_until_aligned_forward
+
+ 1:
+ REG_L t1, ( 0 * SZREG)(a1)
+ addi a1, a1, SZREG
+ addi t3, t3, SZREG
+ REG_S t1, (-1 * SZREG)(t3)
+ bne t3, t6, 1b
+
+ j byte_copy_forward /* Copy any remaining bytes */
+
+coaligned_copy_reverse:
+ jal t0, byte_copy_until_aligned_reverse
+
+ 1:
+ REG_L t1, (-1 * SZREG)(a4)
+ addi a4, a4, -SZREG
+ addi t4, t4, -SZREG
+ REG_S t1, ( 0 * SZREG)(t4)
+ bne t4, t5, 1b
+
+ j byte_copy_reverse /* Copy any remaining bytes */
+
+/*
+ * These are basically sub-functions within the function. They
+ * are used to byte copy until the dest pointer is in alignment.
+ * At which point, a bulk copy method can be used by the
+ * calling code. These work on the same registers as the bulk
+ * copy loops. Therefore, the register values can be picked
+ * up from where they were left and we avoid code duplication
+ * without any overhead except the call in and return jumps.
+ */
+byte_copy_until_aligned_forward:
+ beq t3, t5, 2f
+ 1:
+ lb t1, 0(a1)
+ addi a1, a1, 1
+ addi t3, t3, 1
+ sb t1, -1(t3)
+ bne t3, t5, 1b
+ 2:
+ jalr zero, 0x0(t0) /* Return to multibyte copy loop */
+
+byte_copy_until_aligned_reverse:
+ beq t4, t6, 2f
+ 1:
+ lb t1, -1(a4)
+ addi a4, a4, -1
+ addi t4, t4, -1
+ sb t1, 0(t4)
+ bne t4, t6, 1b
+ 2:
+ jalr zero, 0x0(t0) /* Return to multibyte copy loop */
+
+/*
+ * Simple byte copy loops.
+ * These will byte copy until they reach the end of data to copy.
+ * At that point, they will call to return from memmove.
+ */
+byte_copy:
+ bltu a1, a0, byte_copy_reverse
+
+byte_copy_forward:
+ beq t3, t4, 2f
+ 1:
+ lb t1, 0(a1)
+ addi a1, a1, 1
+ addi t3, t3, 1
+ sb t1, -1(t3)
+ bne t3, t4, 1b
+ 2:
+ ret
+
+byte_copy_reverse:
+ beq t4, t3, 2f
+ 1:
+ lb t1, -1(a4)
+ addi a4, a4, -1
+ addi t4, t4, -1
+ sb t1, 0(t4)
+ bne t4, t3, 1b
+ 2:
+
+return_from_memmove:
+ ret
--
2.34.1
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