1 files changed, 65 insertions, 0 deletions
diff --git a/lib/i386/lshrdi3.s b/lib/i386/lshrdi3.s
new file mode 100644
index 000000000..5992c2131
--- /dev/null
+++ b/lib/i386/lshrdi3.s
@@ -0,0 +1,65 @@
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+
+// di_int __lshrdi3(di_int input, int count);
+
+// This routine has some extra memory traffic, loading the 64-bit input via two
+// 32-bit loads, then immediately storing it back to the stack via a single 64-bit
+// store.  This is to avoid a write-small, read-large stall.
+// However, if callers of this routine can be safely assumed to store the argument
+// via a 64-bt store, this is unnecessary memory traffic, and should be avoided.
+// It can be turned off by defining the TRUST_CALLERS_USE_64_BIT_STORES macro.
+
+#ifdef __i386__
+#ifdef __SSE2__
+
+.text
+.align 4
+.globl ___lshrdi3
+___lshrdi3:
+	movd	  12(%esp),		%xmm2	// Load count
+#ifndef TRUST_CALLERS_USE_64_BIT_STORES
+	movd	   4(%esp),		%xmm0
+	movd	   8(%esp),		%xmm1
+	punpckldq	%xmm1,		%xmm0	// Load input
+#else
+	movq	   4(%esp),		%xmm0	// Load input
+#endif
+	psrlq		%xmm2,		%xmm0	// shift input by count
+	movd		%xmm0,		%eax
+	psrlq		$32,		%xmm0
+	movd		%xmm0,		%edx
+	ret
+
+#else // Use GPRs instead of SSE2 instructions, if they aren't available.
+
+.text
+.align 4
+.globl ___lshrdi3
+___lshrdi3:
+	movl	  12(%esp),		%ecx	// Load count
+	movl	   8(%esp),		%edx	// Load high
+	movl	   4(%esp),		%eax	// Load low
+	
+	testl		$0x20,		%ecx	// If count >= 32
+	jnz			2f					//    goto 2
+	testl		$0x1f,		%ecx	// If count == 0
+	jz			1f					//    goto 1
+	
+	pushl		%ebx
+	movl		%edx,		%ebx	// copy high
+	shrl		%cl,		%eax	// right shift low by count
+	shrl		%cl,		%edx	// right shift high by count
+	neg			%cl
+	shll		%cl,		%ebx	// left shift high by 32 - count
+	orl			%ebx,		%eax	// or the result into the low word
+	popl		%ebx
+1:	ret
+	
+2:	movl		%edx,		%eax	// Move high to low
+	xorl		%edx,		%edx	// clear high
+	shrl		%cl,		%eax	// shift low by count - 32
+	ret
+	
+#endif // __SSE2__
+#endif // __i386__