diff options
Diffstat (limited to 'libpsn00b/libc/clz.S')
| -rw-r--r-- | libpsn00b/libc/clz.S | 53 |
1 files changed, 53 insertions, 0 deletions
diff --git a/libpsn00b/libc/clz.S b/libpsn00b/libc/clz.S new file mode 100644 index 0000000..1ccff2e --- /dev/null +++ b/libpsn00b/libc/clz.S @@ -0,0 +1,53 @@ +# PSn00bSDK leading zero count intrinsics +# (C) 2022-2023 spicyjpeg - MPL licensed +# +# libgcc provides two functions used internally by GCC to count the number of +# leading zeroes in a value, __clzsi2() (32-bit) and __clzdi2() (64-bit). This +# file overrides them with smaller implementations that make use of the GTE's +# LZCS/LZCR registers. + +.set noreorder + +.set LZCS, $30 +.set LZCR, $31 + +.section .text.__clzsi2, "ax", @progbits +.global __clzsi2 +.type __clzsi2, @function + +__clzsi2: + mtc2 $a0, LZCS + bltz $a0, .Lreturn # if (value & (1 << 31)) return 0 + li $v0, 0 + mfc2 $v0, LZCR # else return GTE_CLZ(value) + +.Lreturn: + jr $ra + nop + +.section .text.__clzdi2, "ax", @progbits +.global __clzdi2 +.type __clzdi2, @function + +__clzdi2: + mtc2 $a1, LZCS + bltz $a1, .Lreturn2 # if (msb & (1 << 31)) return 0 + li $v0, 0 + bnez $a1, .LreturnMSB # else if (msb) return GTE_CLZ(msb) + nop + +.LnoMSB: + mtc2 $a0, LZCS + bltz $a0, .Lreturn2 # else if (lsb & (1 << 31)) return 32 + li $v0, 32 + mfc2 $v0, LZCR # else return 32 + GTE_CLZ(lsb) + + jr $ra + addiu $v0, 32 + +.LreturnMSB: + mfc2 $v0, LZCR + +.Lreturn2: + jr $ra + nop |