1/* 2 * Copyright 2008 Analog Devices Inc. 3 * 4 * Licensed under the Clear BSD license or the GPL-2 (or later) 5 */ 6 7.align 2 8.global ___muldi3; 9.type ___muldi3, STT_FUNC; 10 11#ifdef CONFIG_ARITHMETIC_OPS_L1 12.section .l1.text 13#else 14.text 15#endif 16 17/* 18 R1:R0 * R3:R2 19 = R1.h:R1.l:R0.h:R0.l * R3.h:R3.l:R2.h:R2.l 20[X] = (R1.h * R3.h) * 2^96 21[X] + (R1.h * R3.l + R1.l * R3.h) * 2^80 22[X] + (R1.h * R2.h + R1.l * R3.l + R3.h * R0.h) * 2^64 23[T1] + (R1.h * R2.l + R3.h * R0.l + R1.l * R2.h + R3.l * R0.h) * 2^48 24[T2] + (R1.l * R2.l + R3.l * R0.l + R0.h * R2.h) * 2^32 25[T3] + (R0.l * R2.h + R2.l * R0.h) * 2^16 26[T4] + (R0.l * R2.l) 27 28 We can discard the first three lines marked "X" since we produce 29 only a 64 bit result. So, we need ten 16-bit multiplies. 30 31 Individual mul-acc results: 32[E1] = R1.h * R2.l + R3.h * R0.l + R1.l * R2.h + R3.l * R0.h 33[E2] = R1.l * R2.l + R3.l * R0.l + R0.h * R2.h 34[E3] = R0.l * R2.h + R2.l * R0.h 35[E4] = R0.l * R2.l 36 37 We also need to add high parts from lower-level results to higher ones: 38 E[n]c = E[n] + (E[n+1]c >> 16), where E4c := E4 39 40 One interesting property is that all parts of the result that depend 41 on the sign of the multiplication are discarded. Those would be the 42 multiplications involving R1.h and R3.h, but only the top 16 bit of 43 the 32 bit result depend on the sign, and since R1.h and R3.h only 44 occur in E1, the top half of these results is cut off. 45 So, we can just use FU mode for all of the 16-bit multiplies, and 46 ignore questions of when to use mixed mode. */ 47 48___muldi3: 49 /* [SP] technically is part of the caller's frame, but we can 50 use it as scratch space. */ 51 A0 = R2.H * R1.L, A1 = R2.L * R1.H (FU) || R3 = [SP + 12]; /* E1 */ 52 A0 += R3.H * R0.L, A1 += R3.L * R0.H (FU) || [SP] = R4; /* E1 */ 53 A0 += A1; /* E1 */ 54 R4 = A0.w; 55 A0 = R0.l * R3.l (FU); /* E2 */ 56 A0 += R2.l * R1.l (FU); /* E2 */ 57 58 A1 = R2.L * R0.L (FU); /* E4 */ 59 R3 = A1.w; 60 A1 = A1 >> 16; /* E3c */ 61 A0 += R2.H * R0.H, A1 += R2.L * R0.H (FU); /* E2, E3c */ 62 A1 += R0.L * R2.H (FU); /* E3c */ 63 R0 = A1.w; 64 A1 = A1 >> 16; /* E2c */ 65 A0 += A1; /* E2c */ 66 R1 = A0.w; 67 68 /* low(result) = low(E3c):low(E4) */ 69 R0 = PACK (R0.l, R3.l); 70 /* high(result) = E2c + (E1 << 16) */ 71 R1.h = R1.h + R4.l (NS) || R4 = [SP]; 72 RTS; 73 74.size ___muldi3, .-___muldi3 75