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# 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
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