1%default { "naninst":"mvn r0, #0" } 2 /* 3 * For the JIT: incoming arguments in r0-r1, r2-r3 4 * result in r0 5 * 6 * Compare two floating-point values. Puts 0, 1, or -1 into the 7 * destination register based on the results of the comparison. 8 * 9 * Provide a "naninst" instruction that puts 1 or -1 into r1 depending 10 * on what value we'd like to return when one of the operands is NaN. 11 * 12 * The operation we're implementing is: 13 * if (x == y) 14 * return 0; 15 * else if (x < y) 16 * return -1; 17 * else if (x > y) 18 * return 1; 19 * else 20 * return {-1,1}; // one or both operands was NaN 21 * 22 * The straightforward implementation requires 3 calls to functions 23 * that return a result in r0. We can do it with two calls if our 24 * EABI library supports __aeabi_cfcmple (only one if we want to check 25 * for NaN directly): 26 * check x <= y 27 * if <, return -1 28 * if ==, return 0 29 * check y <= x 30 * if <, return 1 31 * return {-1,1} 32 * 33 * for: cmpl-float, cmpg-float 34 */ 35 /* op vAA, vBB, vCC */ 36 mov r9, r0 @ Save copies - we may need to redo 37 mov r10, r1 38 mov r11, lr @ save return address 39 LDR_PC_LR ".L__aeabi_cfcmple" @ cmp <=: C clear if <, Z set if eq 40 bhi .L${opcode}_gt_or_nan @ C set and Z clear, disambiguate 41 mvncc r0, #0 @ (less than) r0<- -1 42 moveq r0, #0 @ (equal) r0<- 0, trumps less than 43 bx r11 44 @ Test for NaN with a second comparison. EABI forbids testing bit 45 @ patterns, and we can't represent 0x7fc00000 in immediate form, so 46 @ make the library call. 47.L${opcode}_gt_or_nan: 48 mov r0, r10 @ restore in reverse order 49 mov r1, r9 50 LDR_PC_LR ".L__aeabi_cfcmple" @ r0<- Z set if eq, C clear if < 51 movcc r0, #1 @ (greater than) r1<- 1 52 bxcc r11 53 $naninst @ r1<- 1 or -1 for NaN 54 bx r11 55