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+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+
+// float __floatundisf(du_int a);
+
+// Note that there is a hardware instruction, fildll, that does most of what
+// this function needs to do. However, because of our ia32 ABI, it will take
+// a write-small read-large stall, so the software implementation here is
+// actually several cycles faster.
+
+// This is a branch-free implementation. A branchy implementation might be
+// faster for the common case if you know something a priori about the input
+// distribution.
+
+/* branch-free x87 implementation - one cycle slower than without x87.
+
+#ifdef __i386__
+
+.const
+.align 3
+
+ .quad 0x43f0000000000000
+twop64: .quad 0x0000000000000000
+
+#define TWOp64 twop64-0b(%ecx,%eax,8)
+
+.text
+.align 4
+.globl ___floatundisf
+___floatundisf:
+ movl 8(%esp), %eax
+ movd 8(%esp), %xmm1
+ movd 4(%esp), %xmm0
+ punpckldq %xmm1, %xmm0
+ calll 0f
+0: popl %ecx
+ sarl $31, %eax
+ movq %xmm0, 4(%esp)
+ fildll 4(%esp)
+ faddl TWOp64
+ fstps 4(%esp)
+ flds 4(%esp)
+ ret
+
+#endif // __i386__
+
+*/
+
+/* branch-free, x87-free implementation - faster at the expense of code size */
+
+#ifdef __i386__
+
+.const
+.align 3
+twop52: .quad 0x4330000000000000
+ .quad 0x0000000000000fff
+sticky: .quad 0x0000000000000000
+ .long 0x00000012
+twelve: .long 0x00000000
+
+#define TWOp52 twop52-0b(%ecx)
+#define STICKY sticky-0b(%ecx,%eax,8)
+
+.text
+.align 4
+.globl ___floatundisf
+___floatundisf:
+ movl 8(%esp), %eax
+ movd 8(%esp), %xmm1
+ movd 4(%esp), %xmm0
+ punpckldq %xmm1, %xmm0
+
+ calll 0f
+0: popl %ecx
+ shrl %eax // high 31 bits of input as sint32
+ addl $0x7ff80000, %eax
+ sarl $31, %eax // (big input) ? -1 : 0
+ movsd STICKY, %xmm1 // (big input) ? 0xfff : 0
+ movl $12, %edx
+ andl %eax, %edx // (big input) ? 12 : 0
+ movd %edx, %xmm3
+ andpd %xmm0, %xmm1 // (big input) ? input & 0xfff : 0
+ movsd TWOp52, %xmm2 // 0x1.0p52
+ psrlq %xmm3, %xmm0 // (big input) ? input >> 12 : input
+ orpd %xmm2, %xmm1 // 0x1.0p52 + ((big input) ? input & 0xfff : input)
+ orpd %xmm1, %xmm0 // 0x1.0p52 + ((big input) ? (input >> 12 | input & 0xfff) : input)
+ subsd %xmm2, %xmm0 // (double)((big input) ? (input >> 12 | input & 0xfff) : input)
+ cvtsd2ss %xmm0, %xmm0 // (float)((big input) ? (input >> 12 | input & 0xfff) : input)
+ pslld $23, %xmm3
+ paddd %xmm3, %xmm0 // (float)input
+ movd %xmm0, 4(%esp)
+ flds 4(%esp)
+ ret
+
+#endif // __i386__