From ab03d3be21f229be8c28dba292d5da237a929a73 Mon Sep 17 00:00:00 2001 From: Miquel Sabaté Solà Date: Wed, 28 Aug 2024 22:25:56 +0200 Subject: Restructure the whole thing MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit It will be something more than just messing around with RISC-V stuff. Signed-off-by: Miquel Sabaté Solà --- arch/riscv/usr/factorial.S | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+) create mode 100644 arch/riscv/usr/factorial.S (limited to 'arch/riscv/usr/factorial.S') diff --git a/arch/riscv/usr/factorial.S b/arch/riscv/usr/factorial.S new file mode 100644 index 0000000..7e3df12 --- /dev/null +++ b/arch/riscv/usr/factorial.S @@ -0,0 +1,28 @@ +.text +.globl factorial +.type factorial, @function + +factorial: + // If input <= 1, just return the given thing. + addi t0, zero, 1 + bgt a0, t0, else + jr ra +else: + // Preserve the argument and the return address before the call. + addi sp, sp, -16 + sd a0, 0(sp) + sd ra, 8(sp) + + // Call the same function but with a value of argument-1. + addi a0, a0, -1 + call factorial + + // Restore back the original argument and the return address. Then multiply + // the original argument with the returned one from the previous call. + ld t1, 0(sp) + ld ra, 8(sp) + addi sp, sp, 16 + mul a0, t1, a0 + + // And return to the caller. + jr ra -- cgit v1.2.3