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Diffstat (limited to 'src/example/strncpy.s')
| -rw-r--r-- | src/example/strncpy.s | 36 |
1 files changed, 36 insertions, 0 deletions
diff --git a/src/example/strncpy.s b/src/example/strncpy.s new file mode 100644 index 0000000..87e5410 --- /dev/null +++ b/src/example/strncpy.s @@ -0,0 +1,36 @@ + .text + .balign 4 + .global strncpy + # char* strncpy(char *dst, const char* src, size_t n) +strncpy: + mv a3, a0 # Copy dst +loop: + vsetvli x0, a2, e8, m8, ta, ma # Vectors of bytes. + vle8ff.v v8, (a1) # Get src bytes + vmseq.vi v1, v8, 0 # Flag zero bytes + csrr t1, vl # Get number of bytes fetched + vfirst.m a4, v1 # Zero found? + vmsbf.m v0, v1 # Set mask up to before zero byte. + vse8.v v8, (a3), v0.t # Write out non-zero bytes + bgez a4, zero_tail # Zero remaining bytes. + sub a2, a2, t1 # Decrement count. + add a3, a3, t1 # Bump dest pointer + add a1, a1, t1 # Bump src pointer + bnez a2, loop # Anymore? + + ret + +zero_tail: + sub a2, a2, a4 # Subtract count on non-zero bytes. + add a3, a3, a4 # Advance past non-zero bytes. + vsetvli t1, a2, e8, m8, ta, ma # Vectors of bytes. + vmv.v.i v0, 0 # Splat zero. + +zero_loop: + vse8.v v0, (a3) # Store zero. + sub a2, a2, t1 # Decrement count. + add a3, a3, t1 # Bump pointer + vsetvli t1, a2, e8, m8, ta, ma # Vectors of bytes. + bnez a2, zero_loop # Anymore? + + ret |