lshrdi3.S revision 2d1fdb26e458c4ddc04155c1d421bced3ba90cd0 
1// This file is dual licensed under the MIT and the University of Illinois Open
2// Source Licenses. See LICENSE.TXT for details.
3
4#include "../assembly.h"
5
6// di_int __lshrdi3(di_int input, int count);
7
8// This routine has some extra memory traffic, loading the 64-bit input via two
9// 32-bit loads, then immediately storing it back to the stack via a single 64-bit
10// store.  This is to avoid a write-small, read-large stall.
11// However, if callers of this routine can be safely assumed to store the argument
12// via a 64-bt store, this is unnecessary memory traffic, and should be avoided.
13// It can be turned off by defining the TRUST_CALLERS_USE_64_BIT_STORES macro.
14
15#ifdef __i386__
16#ifdef __SSE2__
17
18.text
19.balign 4
20DEFINE_COMPILERRT_FUNCTION(__lshrdi3)
21	movd	  12(%esp),		%xmm2	// Load count
22#ifndef TRUST_CALLERS_USE_64_BIT_STORES
23	movd	   4(%esp),		%xmm0
24	movd	   8(%esp),		%xmm1
25	punpckldq	%xmm1,		%xmm0	// Load input
26#else
27	movq	   4(%esp),		%xmm0	// Load input
28#endif
29	psrlq		%xmm2,		%xmm0	// shift input by count
30	movd		%xmm0,		%eax
31	psrlq		$32,		%xmm0
32	movd		%xmm0,		%edx
33	ret
34END_COMPILERRT_FUNCTION(__lshrdi3)
35
36#else // Use GPRs instead of SSE2 instructions, if they aren't available.
37
38.text
39.balign 4
40DEFINE_COMPILERRT_FUNCTION(__lshrdi3)
41	movl	  12(%esp),		%ecx	// Load count
42	movl	   8(%esp),		%edx	// Load high
43	movl	   4(%esp),		%eax	// Load low
44
45	testl		$0x20,		%ecx	// If count >= 32
46	jnz			1f					//    goto 1
47
48	shrdl		%cl, %edx,	%eax	// right shift low by count
49	shrl		%cl,		%edx	// right shift high by count
50	ret
51
521:	movl		%edx,		%eax	// Move high to low
53	xorl		%edx,		%edx	// clear high
54	shrl		%cl,		%eax	// shift low by count - 32
55	ret
56END_COMPILERRT_FUNCTION(__lshrdi3)
57
58#endif // __SSE2__
59#endif // __i386__
60