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[ipdf/code.git] / src / div_digits_asm.S

diff --git a/src/div_digits_asm.S b/src/div_digits_asm.S
new file mode 100644 (file)
index 0000000..5dd5504
--- /dev/null
+++ b/src/div_digits_asm.S
@@ -0,0 +1,33 @@
+.section .text
+.globl div_digits
+.type div_digits, @function
+
+#ifdef __x86_64__
+
+# div_digits(digits, div, size, res)
+# divides an arbint in digits by uint64 div into res, returns remainder
+# res may alias digits
+# digits = rdi, div = rsx, size = rdx, res = rcx,
+div_digits:
+       movq %rdx, %r8
+       leaq -8(%rdi,%r8,8), %rdi       # We want to point to the end of the buffer (LSB)
+       leaq -8(%rcx,%r8,8), %rcx       # We want to point to the end of the buffer (LSB)
+       movq $0, %rdx
+loop:
+       movq (%rdi), %rax
+       divq %rsi                       # rdx:rax/rsi => rax, rdx:rax%rsi => rdx
+       movq %rax, (%rcx)
+       dec %r8
+       leaq -8(%rdi), %rdi
+       leaq -8(%rcx), %rcx
+       jnz loop
+end:
+       movq %rdx, %rax                 # return the remainder
+       ret
+       
+#else
+
+div_digits:
+       ret
+
+#endif