Merge pull request #68 from spicyjpeg/bugfix

Bugfixes, psxcd rewrite, psxgpu and CMake tweaks (v0.22)

1 files changed, 43 insertions, 0 deletions

diff --git a/libpsn00b/libc/clz.s b/libpsn00b/libc/clz.s
new file mode 100644
index 0000000..28a28eb
--- /dev/null
+++ b/libpsn00b/libc/clz.s
@@ -0,0 +1,43 @@
+# PSn00bSDK leading zero count intrinsics
+# (C) 2022 spicyjpeg - MPL licensed
+#
+# libgcc provides two functions used internally by GCC to count the number of 
+# leading zeroes or ones in a value, _clzsi2() (32-bit) and _clzdi2() (64-bit).
+# This file overrides them with faster implementations that make use of the
+# GTE's LZCS/LZCR registers.
+
+.set noreorder
+
+.section .text._clzsi2
+.global _clzsi2
+.type _clzsi2, @function
+_clzsi2:
+	mtc2 $a0, $30
+	nop
+	nop
+	mfc2 $v0, $31
+
+	jr   $ra
+	nop
+
+.section .text._clzdi2
+.global _clzdi2
+.type _clzdi2, @function
+_clzdi2:
+	bnez $a1, .Lhas_msb
+	nop
+
+	mtc2 $a0, $30 # if (!msb) return 32 + clz(lsb)
+	b    .Lreturn
+	li   $v1, 32
+
+.Lhas_msb:
+	mtc2 $a1, $30  # if (msb) return 0 + clz(msb)
+	nop
+	li   $v1, 0
+
+.Lreturn:
+	mfc2 $v0, $31
+
+	jr   $ra
+	addu $v0, $v1