[FFmpeg-devel] [PATCH 6/7] avutil/riscv/asm: add generic push/pop helpers

["J. Dekker" <jdek@itanimul.li>]

From: Niklas Haas <git@haasn.dev>

Generic helper macros to push/pop multiple registers at once. Expands to
a single `addi` plus a sequence of XLEN-sized stores/loads.
---
 libavutil/riscv/asm.S | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/libavutil/riscv/asm.S b/libavutil/riscv/asm.S
index db190e99ca..3955530e4e 100644
--- a/libavutil/riscv/asm.S
+++ b/libavutil/riscv/asm.S
@@ -288,3 +288,40 @@
         .macro  count_args args:vararg
         count_args_inner 0, \args
         .endm
+
+        /**
+         * Helper macro to iterate over constant sized elements in memory
+         * @param op operation to perform on each element (sized load/store)
+         * @param size size in bytes per element
+         * @param offset starting offset of first element
+         * @param addr base address to load/store
+         * @param regs registers to iterate over
+         */
+        .macro  for_mem op, size, offset, addr, reg, regs:vararg
+        .ifnb \reg
+        \op     \reg, \offset(\addr)
+        for_mem \op, \size, \offset + \size, \addr, \regs
+        .endif
+        .endm
+
+        /**
+         * Push a variable number of registers to the stack.
+         * @param n number of registers to push
+         * @param regs registers to push
+         */
+        .macro  push regs:vararg
+        count_args \regs
+        addi    sp, sp, -(num_args * (__riscv_xlen >> 3))
+        for_mem sx, __riscv_xlen >> 3, 0, sp, \regs
+        .endm
+
+        /**
+         * Pop a variable number of registers from the stack.
+         * @param n number of registers to pop
+         * @param[out] regs registers to pop
+         */
+        .macro  pop regs:vararg
+        count_args \regs
+        for_mem lx, __riscv_xlen >> 3, 0, sp, \regs
+        addi    sp, sp, num_args * (__riscv_xlen >> 3)
+        .endm
-- 
2.45.1

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