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-rw-r--r--third_party/aom/build/make/thumb.pm71
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diff --git a/third_party/aom/build/make/thumb.pm b/third_party/aom/build/make/thumb.pm
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+++ b/third_party/aom/build/make/thumb.pm
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+#!/usr/bin/env perl
+##
+## Copyright (c) 2016, Alliance for Open Media. All rights reserved
+##
+## This source code is subject to the terms of the BSD 2 Clause License and
+## the Alliance for Open Media Patent License 1.0. If the BSD 2 Clause License
+## was not distributed with this source code in the LICENSE file, you can
+## obtain it at www.aomedia.org/license/software. If the Alliance for Open
+## Media Patent License 1.0 was not distributed with this source code in the
+## PATENTS file, you can obtain it at www.aomedia.org/license/patent.
+##
+
+package thumb;
+
+sub FixThumbInstructions($$)
+{
+ my $short_branches = $_[1];
+ my $branch_shift_offset = $short_branches ? 1 : 0;
+
+ # 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 a conditional addition to the pc register into a series of
+ # instructions. This converts "addlt pc, pc, r3, lsl #2" into
+ # "itttt lt", "movlt.n r12, pc", "addlt.w r12, #12",
+ # "addlt.w r12, r12, r3, lsl #2", "movlt.n pc, r12".
+ # This assumes that r12 is free at this point.
+ s/^(\s*)addlt(\s+)pc,\s*pc,\s*(\w+),\s*lsl\s*#(\d+)/$1itttt$2lt\n$1movlt.n$2r12, pc\n$1addlt.w$2r12, #12\n$1addlt.w$2r12, r12, $3, lsl #($4-$branch_shift_offset)\n$1movlt.n$2pc, r12/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;