diff options
Diffstat (limited to 'newasm/regregimm.s')
| -rw-r--r-- | newasm/regregimm.s | 47 |
1 files changed, 47 insertions, 0 deletions
diff --git a/newasm/regregimm.s b/newasm/regregimm.s new file mode 100644 index 0000000..6c649e2 --- /dev/null +++ b/newasm/regregimm.s @@ -0,0 +1,47 @@ +.syntax unified +.cpu cortex-m0plus +.thumb + +.type regregimm, %function +.global regregimm + +// R1 instruction under construction +// R3 immediate width +// R4 input buffer + +regregimm:PUSH {LR} + PUSH {R3} + BL register // parse a register + POP {R3} + BNE exit // exit if failure + CMP R2, 7 // check that it's R0-R7 + BHI bad_reg + ORRS R1, R2 // fill in Rd + BL whitespace // mandatory whitespace + BNE exit // exit if failure + PUSH {R3} + BL register // parse a register + POP {R3} + BNE exit + CMP R2, 7 // check that it's R0-R7 + BHI bad_reg + LSLS R2, 3 // shift by 3 + ORRS R1, R2 // fill in Rn + BL whitespace // mandatory whitespace + BNE exit // exit if failure + PUSH {R3} + BL immediate + POP {R3} + BNE exit + MOVS R0, 1 + LSLS R0, R3 + CMP R2, R0 + BLO fine + MOVS R0, 0x0A // returun code 0A (immediate value too large) + POP {PC} +fine: LSLS R2, 6 // shift by 6 + ORRS R1, R2 // fill in imm + MOVS R0, 0 // return code 0 (success) +exit: POP {PC} +bad_reg: MOVS R0, 8 // return code 8 (invalid register for this register position) + POP {PC} |