Initial import of compiler-rt.
-
git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@74292 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/i386/udivdi3.s b/lib/i386/udivdi3.s
new file mode 100644
index 0000000..977cee3
--- /dev/null
+++ b/lib/i386/udivdi3.s
@@ -0,0 +1,113 @@
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+
+// du_int __udivdi3(du_int a, du_int b);
+
+// result = a / b.
+// both inputs and the output are 64-bit unsigned integers.
+// This will do whatever the underlying hardware is set to do on division by zero.
+// No other exceptions are generated, as the divide cannot overflow.
+//
+// This is targeted at 32-bit x86 *only*, as this can be done directly in hardware
+// on x86_64. The performance goal is ~40 cycles per divide, which is faster than
+// currently possible via simulation of integer divides on the x87 unit.
+//
+// Stephen Canon, December 2008
+
+#ifdef __i386__
+
+.text
+.align 4
+.globl ___udivdi3
+___udivdi3:
+
+ pushl %ebx
+ movl 20(%esp), %ebx // Find the index i of the leading bit in b.
+ bsrl %ebx, %ecx // If the high word of b is zero, jump to
+ jz 9f // the code to handle that special case [9].
+
+ /* High word of b is known to be non-zero on this branch */
+
+ movl 16(%esp), %eax // Construct bhi, containing bits [1+i:32+i] of b
+
+ shrl %cl, %eax // Practically, this means that bhi is given by:
+ shrl %eax //
+ notl %ecx // bhi = (high word of b) << (31 - i) |
+ shll %cl, %ebx // (low word of b) >> (1 + i)
+ orl %eax, %ebx //
+ movl 12(%esp), %edx // Load the high and low words of a, and jump
+ movl 8(%esp), %eax // to [1] if the high word is larger than bhi
+ cmpl %ebx, %edx // to avoid overflowing the upcoming divide.
+ jae 1f
+
+ /* High word of a is greater than or equal to (b >> (1 + i)) on this branch */
+
+ divl %ebx // eax <-- qs, edx <-- r such that ahi:alo = bs*qs + r
+
+ pushl %edi
+ notl %ecx
+ shrl %eax
+ shrl %cl, %eax // q = qs >> (1 + i)
+ movl %eax, %edi
+ mull 20(%esp) // q*blo
+ movl 12(%esp), %ebx
+ movl 16(%esp), %ecx // ECX:EBX = a
+ subl %eax, %ebx
+ sbbl %edx, %ecx // ECX:EBX = a - q*blo
+ movl 24(%esp), %eax
+ imull %edi, %eax // q*bhi
+ subl %eax, %ecx // ECX:EBX = a - q*b
+ sbbl $0, %edi // decrement q if remainder is negative
+ xorl %edx, %edx
+ movl %edi, %eax
+ popl %edi
+ popl %ebx
+ retl
+
+
+1: /* High word of a is greater than or equal to (b >> (1 + i)) on this branch */
+
+ subl %ebx, %edx // subtract bhi from ahi so that divide will not
+ divl %ebx // overflow, and find q and r such that
+ //
+ // ahi:alo = (1:q)*bhi + r
+ //
+ // Note that q is a number in (31-i).(1+i)
+ // fix point.
+
+ pushl %edi
+ notl %ecx
+ shrl %eax
+ orl $0x80000000, %eax
+ shrl %cl, %eax // q = (1:qs) >> (1 + i)
+ movl %eax, %edi
+ mull 20(%esp) // q*blo
+ movl 12(%esp), %ebx
+ movl 16(%esp), %ecx // ECX:EBX = a
+ subl %eax, %ebx
+ sbbl %edx, %ecx // ECX:EBX = a - q*blo
+ movl 24(%esp), %eax
+ imull %edi, %eax // q*bhi
+ subl %eax, %ecx // ECX:EBX = a - q*b
+ sbbl $0, %edi // decrement q if remainder is negative
+ xorl %edx, %edx
+ movl %edi, %eax
+ popl %edi
+ popl %ebx
+ retl
+
+
+9: /* High word of b is zero on this branch */
+
+ movl 12(%esp), %eax // Find qhi and rhi such that
+ movl 16(%esp), %ecx //
+ xorl %edx, %edx // ahi = qhi*b + rhi with 0 ≤ rhi < b
+ divl %ecx //
+ movl %eax, %ebx //
+ movl 8(%esp), %eax // Find qlo such that
+ divl %ecx //
+ movl %ebx, %edx // rhi:alo = qlo*b + rlo with 0 ≤ rlo < b
+ popl %ebx //
+ retl // and return qhi:qlo
+
+#endif // __i386__