| #!/usr/bin/env perl |
| ## |
| ## Copyright (c) 2013 The WebM project authors. All Rights Reserved. |
| ## |
| ## Use of this source code is governed by a BSD-style license |
| ## that can be found in the LICENSE file in the root of the source |
| ## tree. An additional intellectual property rights grant can be found |
| ## in the file PATENTS. All contributing project authors may |
| ## be found in the AUTHORS file in the root of the source tree. |
| ## |
| |
| package thumb; |
| |
| sub FixThumbInstructions($) |
| { |
| # Write additions with shifts, such as "add r10, r11, lsl #8", |
| # in three operand form, "add r10, r10, r11, lsl #8". |
| s/(add\s+)(r\d+),\s*(r\d+),\s*(lsl #\d+)/$1$2, $2, $3, $4/g; |
| |
| # Convert additions with a non-constant shift into a sequence |
| # with left shift, addition and a right shift (to restore the |
| # register to the original value). Currently the right shift |
| # isn't necessary in the code base since the values in these |
| # registers aren't used, but doing the shift for consistency. |
| # This converts instructions such as "add r12, r12, r5, lsl r4" |
| # into the sequence "lsl r5, r4", "add r12, r12, r5", "lsr r5, r4". |
| s/^(\s*)(add)(\s+)(r\d+),\s*(r\d+),\s*(r\d+),\s*lsl (r\d+)/$1lsl$3$6, $7\n$1$2$3$4, $5, $6\n$1lsr$3$6, $7/g; |
| |
| # Convert loads with right shifts in the indexing into a |
| # sequence of an add, load and sub. This converts |
| # "ldrb r4, [r9, lr, asr #1]" into "add r9, r9, lr, asr #1", |
| # "ldrb r9, [r9]", "sub r9, r9, lr, asr #1". |
| s/^(\s*)(ldrb)(\s+)(r\d+),\s*\[(\w+),\s*(\w+),\s*(asr #\d+)\]/$1add $3$5, $5, $6, $7\n$1$2$3$4, [$5]\n$1sub $3$5, $5, $6, $7/g; |
| |
| # Convert register indexing with writeback into a separate add |
| # instruction. This converts "ldrb r12, [r1, r2]!" into |
| # "ldrb r12, [r1, r2]", "add r1, r1, r2". |
| s/^(\s*)(ldrb)(\s+)(r\d+),\s*\[(\w+),\s*(\w+)\]!/$1$2$3$4, [$5, $6]\n$1add $3$5, $6/g; |
| |
| # Convert negative register indexing into separate sub/add instructions. |
| # This converts "ldrne r4, [src, -pstep, lsl #1]" into |
| # "subne src, src, pstep, lsl #1", "ldrne r4, [src]", |
| # "addne src, src, pstep, lsl #1". In a couple of cases where |
| # this is used, it's used for two subsequent load instructions, |
| # where a hand-written version of it could merge two subsequent |
| # add and sub instructions. |
| s/^(\s*)((ldr|str|pld)(ne)?)(\s+)(r\d+,\s*)?\[(\w+), -([^\]]+)\]/$1sub$4$5$7, $7, $8\n$1$2$5$6\[$7\]\n$1add$4$5$7, $7, $8/g; |
| |
| # Convert register post indexing to a separate add instruction. |
| # This converts "ldrneb r9, [r0], r2" into "ldrneb r9, [r0]", |
| # "addne r0, r0, r2". |
| s/^(\s*)((ldr|str)(ne)?[bhd]?)(\s+)(\w+),(\s*\w+,)?\s*\[(\w+)\],\s*(\w+)/$1$2$5$6,$7 [$8]\n$1add$4$5$8, $8, $9/g; |
| |
| # Convert "mov pc, lr" into "bx lr", since the former only works |
| # for switching from arm to thumb (and only in armv7), but not |
| # from thumb to arm. |
| s/mov(\s*)pc\s*,\s*lr/bx$1lr/g; |
| } |
| |
| 1; |