Blackfin arch: add assembly function for doing 64bit unsigned division

Signed-off-by: Mike Frysinger <michael.frysinger@analog.com>
Signed-off-by: Bryan Wu <bryan.wu@analog.com>

arch/blackfin/lib/Makefile

@@ -4,7 +4,7 @@
 
 lib-y := \
 	ashldi3.o ashrdi3.o lshrdi3.o \
-	muldi3.o divsi3.o udivsi3.o modsi3.o umodsi3.o \
+	muldi3.o divsi3.o udivsi3.o udivdi3.o modsi3.o umodsi3.o \
 	checksum.o memcpy.o memset.o memcmp.o memchr.o memmove.o \
 	strcmp.o strcpy.o strncmp.o strncpy.o \
 	umulsi3_highpart.o smulsi3_highpart.o \

arch/blackfin/lib/udivdi3.S

+/*
+ * udivdi3.S - unsigned long long division
+ *
+ * Copyright 2003-2007 Analog Devices Inc.
+ * Enter bugs at http://blackfin.uclinux.org/
+ *
+ * Licensed under the GPLv2 or later.
+ */
+
+#include <linux/linkage.h>
+
+#define CARRY AC0
+
+#ifdef CONFIG_ARITHMETIC_OPS_L1
+.section .l1.text
+#else
+.text
+#endif
+
+
+ENTRY(___udivdi3)
+   R3 = [SP + 12];
+   [--SP] = (R7:4, P5:3);
+
+   /* Attempt to use divide primitive first; these will handle
+   **  most cases, and they're quick - avoids stalls incurred by
+   ** testing for identities.
+   */
+
+   R4 = R2 | R3;
+   CC = R4 == 0;
+   IF CC JUMP .LDIV_BY_ZERO;
+
+   R4.H = 0x8000;
+   R4 >>>= 16;                  // R4 now 0xFFFF8000
+   R5 = R0 | R2;                // If either dividend or
+   R4 = R5 & R4;                // divisor have bits in
+   CC = R4;                     // top half or low half's sign
+   IF CC JUMP .LIDENTS;          // bit, skip builtins.
+   R4 = R1 | R3;                // Also check top halves
+   CC = R4;
+   IF CC JUMP .LIDENTS;
+
+   /* Can use the builtins. */
+
+   AQ = CC;                     // Clear AQ (CC==0)
+   DIVQ(R0, R2);
+   DIVQ(R0, R2);
+   DIVQ(R0, R2);
+   DIVQ(R0, R2);
+   DIVQ(R0, R2);
+   DIVQ(R0, R2);
+   DIVQ(R0, R2);
+   DIVQ(R0, R2);
+   DIVQ(R0, R2);
+   DIVQ(R0, R2);
+   DIVQ(R0, R2);
+   DIVQ(R0, R2);
+   DIVQ(R0, R2);
+   DIVQ(R0, R2);
+   DIVQ(R0, R2);
+   DIVQ(R0, R2);
+   DIVQ(R0, R2);
+   R0 = R0.L (Z);
+   R1 = 0;
+   (R7:4, P5:3) = [SP++];
+   RTS;
+
+.LIDENTS:
+   /* Test for common identities. Value to be returned is
+   ** placed in R6,R7.
+   */
+                                // Check for 0/y, return 0
+   R4 = R0 | R1;
+   CC = R4 == 0;
+   IF CC JUMP .LRETURN_R0;
+
+                                // Check for x/x, return 1
+   R6 = R0 - R2;                // If x == y, then both R6 and R7 will be zero
+   R7 = R1 - R3;
+   R4 = R6 | R7;                // making R4 zero.
+   R6 += 1;                     // which would now make R6:R7==1.
+   CC = R4 == 0;
+   IF CC JUMP .LRETURN_IDENT;
+
+                                // Check for x/1, return x
+   R6 = R0;
+   R7 = R1;
+   CC = R3 == 0;
+   IF !CC JUMP .Lnexttest;
+   CC = R2 == 1;
+   IF CC JUMP .LRETURN_IDENT;
+
+.Lnexttest:
+   R4.L = ONES R2;              // check for div by power of two which
+   R5.L = ONES R3;              // can be done using a shift
+   R6 = PACK (R5.L, R4.L);
+   CC = R6 == 1;
+   IF CC JUMP .Lpower_of_two_upper_zero;
+   R6 = PACK (R4.L, R5.L);
+   CC = R6 == 1;
+   IF CC JUMP .Lpower_of_two_lower_zero;
+
+                                // Check for x < y, return 0
+   R6 = 0;
+   R7 = R6;
+   CC = R1 < R3 (IU);
+   IF CC JUMP .LRETURN_IDENT;
+   CC = R1 == R3;
+   IF !CC JUMP .Lno_idents;
+   CC = R0 < R2 (IU);
+   IF CC JUMP .LRETURN_IDENT;
+
+.Lno_idents:                    // Idents don't match. Go for the full operation
+
+
+   // If X, or X and Y have high bit set, it'll affect the
+   // results, so shift right one to stop this. Note: we've already
+   // checked that X >= Y, so Y's msb won't be set unless X's
+   // is.
+
+   R4 = 0;
+   CC = R1 < 0;
+   IF !CC JUMP .Lx_msb_clear;
+   CC = !CC;                   // 1 -> 0;
+   R1 = ROT R1 BY -1;          // Shift X >> 1
+   R0 = ROT R0 BY -1;          // lsb -> CC
+   BITSET(R4,31);              // to record only x msb was set
+   CC = R3 < 0;
+   IF !CC JUMP .Ly_msb_clear;
+   CC = !CC;
+   R3 = ROT R3 BY -1;          // Shift Y >> 1
+   R2 = ROT R2 BY -1;
+   BITCLR(R4,31);              // clear bit to record only x msb was set
+
+.Ly_msb_clear:
+.Lx_msb_clear:
+   // Bit 31 in R4 indicates X msb set, but Y msb wasn't, and no bits
+   // were lost, so we should shift result left by one.
+
+   [--SP] = R4;                // save for later
+
+   // In the loop that follows, each iteration we add
+   // either Y' or -Y' to the Remainder. We compute the
+   // negated Y', and store, for convenience. Y' goes
+   // into P0:P1, while -Y' goes into P2:P3.
+
+   P0 = R2;
+   P1 = R3;
+   R2 = -R2;
+   CC = CARRY;
+   CC = !CC;
+   R4 = CC;
+   R3 = -R3;
+   R3 = R3 - R4;
+
+   R6 = 0;                     // remainder = 0
+   R7 = R6;
+
+   [--SP] = R2; P2 = SP;
+   [--SP] = R3; P3 = SP;
+   [--SP] = R6; P5 = SP;       // AQ = 0
+   [--SP] = P1;
+
+   /* In the loop that follows, we use the following
+   ** register assignments:
+   ** R0,R1 X, workspace
+   ** R2,R3 Y, workspace
+   ** R4,R5 partial Div
+   ** R6,R7 partial remainder
+   ** P5 AQ
+   ** The remainder and div form a 128-bit number, with
+   ** the remainder in the high 64-bits.
+   */
+   R4 = R0;                    // Div = X'
+   R5 = R1;
+   R3 = 0;
+
+   P4 = 64;                    // Iterate once per bit
+   LSETUP(.LULST,.LULEND) LC0 = P4;
+.LULST:
+        /* Shift Div and remainder up by one. The bit shifted
+        ** out of the top of the quotient is shifted into the bottom
+        ** of the remainder.
+        */
+        CC = R3;
+        R4 = ROT R4 BY 1;
+        R5 = ROT R5 BY 1 ||        // low q to high q
+             R2 = [P5];            // load saved AQ
+        R6 = ROT R6 BY 1 ||        // high q to low r
+             R0 = [P2];            // load -Y'
+        R7 = ROT R7 BY 1 ||        // low r to high r
+             R1 = [P3];
+
+                                   // Assume add -Y'
+        CC = R2 < 0;               // But if AQ is set...
+        IF CC R0 = P0;             // then add Y' instead
+        IF CC R1 = P1;
+
+        R6 = R6 + R0;              // Rem += (Y' or -Y')
+        CC = CARRY;
+        R0 = CC;
+        R7 = R7 + R1;
+        R7 = R7 + R0 (NS) ||
+             R1 = [SP];
+                                   // Set the next AQ bit
+        R1 = R7 ^ R1;              // from Remainder and Y'
+        R1 = R1 >> 31 ||           // Negate AQ's value, and
+             [P5] = R1;            // save next AQ
+        BITTGL(R1, 0);             // add neg AQ  to the Div
+.LULEND: R4 = R4 + R1;
+
+   R6 = [SP + 16];
+
+   R0 = R4;
+   R1 = R5;
+   CC = BITTST(R6,30);         // Just set CC=0
+   R4 = ROT R0 BY 1;           // but if we had to shift X,
+   R5 = ROT R1 BY 1;           // and didn't shift any bits out,
+   CC = BITTST(R6,31);         // then the result will be half as
+   IF CC R0 = R4;              // much as required, so shift left
+   IF CC R1 = R5;              // one space.
+
+   SP += 20;
+   (R7:4, P5:3) = [SP++];
+   RTS;
+
+.Lpower_of_two:
+   /* Y has a single bit set, which means it's a power of two.
+   ** That means we can perform the division just by shifting
+   ** X to the right the appropriate number of bits
+   */
+
+   /* signbits returns the number of sign bits, minus one.
+   ** 1=>30, 2=>29, ..., 0x40000000=>0. Which means we need
+   ** to shift right n-signbits spaces. It also means 0x80000000
+   ** is a special case, because that *also* gives a signbits of 0
+   */
+.Lpower_of_two_lower_zero:
+   R7 = 0;
+   R6 = R1 >> 31;
+   CC = R3 < 0;
+   IF CC JUMP .LRETURN_IDENT;
+
+   R2.L = SIGNBITS R3;
+   R2 = R2.L (Z);
+   R2 += -62;
+   (R7:4, P5:3) = [SP++];
+   JUMP ___lshftli;
+
+.Lpower_of_two_upper_zero:
+   CC = R2 < 0;
+   IF CC JUMP .Lmaxint_shift;
+
+   R2.L = SIGNBITS R2;
+   R2 = R2.L (Z);
+   R2 += -30;
+   (R7:4, P5:3) = [SP++];
+   JUMP ___lshftli;
+
+.Lmaxint_shift:
+   R2 = -31;
+   (R7:4, P5:3) = [SP++];
+   JUMP ___lshftli;
+
+.LRETURN_IDENT:
+   R0 = R6;
+   R1 = R7;
+.LRETURN_R0:
+   (R7:4, P5:3) = [SP++];
+   RTS;
+.LDIV_BY_ZERO:
+   R0 = ~R2;
+   R1 = R0;
+   (R7:4, P5:3) = [SP++];
+   RTS;
+
+ENDPROC(___udivdi3)
+
+
+ENTRY(___lshftli)
+	CC = R2 == 0;
+	IF CC JUMP .Lfinished;	// nothing to do
+	CC = R2 < 0;
+	IF CC JUMP .Lrshift;
+	R3 = 64;
+	CC = R2 < R3;
+	IF !CC JUMP .Lretzero;
+
+	// We're shifting left, and it's less than 64 bits, so
+	// a valid result will be returned.
+
+	R3 >>= 1;	// R3 now 32
+	CC = R2 < R3;
+
+	IF !CC JUMP .Lzerohalf;
+
+	// We're shifting left, between 1 and 31 bits, which means
+	// some of the low half will be shifted into the high half.
+	// Work out how much.
+
+	R3 = R3 - R2;
+
+	// Save that much data from the bottom half.
+
+	P1 = R7;
+	R7 = R0;
+	R7 >>= R3;
+
+	// Adjust both parts of the parameter.
+
+	R0 <<= R2;
+	R1 <<= R2;
+
+	// And include the bits moved across.
+
+	R1 = R1 | R7;
+	R7 = P1;
+	RTS;
+
+.Lzerohalf:
+	// We're shifting left, between 32 and 63 bits, so the
+	// bottom half will become zero, and the top half will
+	// lose some bits. How many?
+
+	R2 = R2 - R3;	// N - 32
+	R1 = LSHIFT R0 BY R2.L;
+	R0 = R0 - R0;
+	RTS;
+
+.Lretzero:
+	R0 = R0 - R0;
+	R1 = R0;
+.Lfinished:
+	RTS;
+
+.Lrshift:
+	// We're shifting right, but by how much?
+	R2 = -R2;
+	R3 = 64;
+	CC = R2 < R3;
+	IF !CC JUMP .Lretzero;
+
+	// Shifting right less than 64 bits, so some result bits will
+	// be retained.
+
+	R3 >>= 1;	// R3 now 32
+	CC = R2 < R3;
+	IF !CC JUMP .Lsignhalf;
+
+	// Shifting right between 1 and 31 bits, so need to copy
+	// data across words.
+
+	P1 = R7;
+	R3 = R3 - R2;
+	R7 = R1;
+	R7 <<= R3;
+	R1 >>= R2;
+	R0 >>= R2;
+	R0 = R7 | R0;
+	R7 = P1;
+	RTS;
+
+.Lsignhalf:
+	// Shifting right between 32 and 63 bits, so the top half
+	// will become all zero-bits, and the bottom half is some
+	// of the top half. But how much?
+
+	R2 = R2 - R3;
+	R0 = R1;
+	R0 >>= R2;
+	R1 = 0;
+	RTS;
+
+ENDPROC(___lshftli)