On 2014-03-17 10:56:49 +0200, Martin Storsjö wrote:
> This does some rudimentary conversions of instructions that aren't
> available in thumb mode.
>
> This allows building OpenH264 for Windows Phone 8 (and Windows RT),
> which only supports thumb mode, and the OpenH264 arm assembly is
> hardcoded for arm mode.
>
> This is similar to how libvpx supports assembling in thumb mode - the
> source itself is arm mode only, but a perl script can replace
> instruction combinations that aren't supported in thumb mode. This
> is a small subset of those conversions.
> ---
> gas-preprocessor.pl | 31 +++++++++++++++++++++++++++++++
> 1 file changed, 31 insertions(+)
>
> diff --git a/gas-preprocessor.pl b/gas-preprocessor.pl
> index 3d1049b..bbc5ff4 100755
> --- a/gas-preprocessor.pl
> +++ b/gas-preprocessor.pl
> @@ -27,6 +27,7 @@ my $arch;
> my $as_type = "apple-gas";
>
> my $fix_unreq = $^O eq "darwin";
> +my $force_thumb = 0;
>
> my $usage_str = "
> $0\n
> @@ -43,6 +44,7 @@ command. Following options are currently supported:
> -as-type - one value out of {{,apple-}{gas,clang},armasm}
> -fix-unreq
> -no-fix-unreq
> + -force-thumb - assemble as thumb regardless of the input source
a warning that it is incomplete will probably only work for sources
it was tested with might be appropriate although nobody will read it.
> ";
>
> sub usage() {
> @@ -74,6 +76,8 @@ while (@options) {
> my $opt = shift @options;
> if ($opt =~ /^-(no-)?fix-unreq$/) {
> $fix_unreq = $1 ne "no-";
> + } elsif ($opt eq "-force-thumb") {
> + $force_thumb = 1;
> } elsif ($opt eq "-arch") {
> $arch = shift @options;
> die "unknown arch: '$arch'\n" if not exists $comments{$arch};
> @@ -213,6 +217,15 @@ my @ifstack;
>
> my %symbols;
>
> +if ($force_thumb) {
> + # This doesn't go through the initial parsing loop below
> + if ($as_type eq "armasm") {
> + parse_line("THUMB\n");
> + } else {
> + parse_line(".thumb\n");
> + }
> +}
> +
> # pass 1: parse .macro
> # note that the handling of arguments is probably overly permissive vs. gas
> # but it should be the same for valid cases
> @@ -883,6 +896,24 @@ sub handle_serialized_line {
> $line =~ s/&0x/& 0x/g;
> }
>
> + if ($force_thumb) {
> + # Convert register post indexing to a separate add instruction.
> + # This converts "ldrneb r9, [r0], r2" into "ldrneb r9, [r0]",
> + # "add r0, r2".
> + $line =~
> 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;
You're removing the condition. If openh264 is open to patches it would
probably a good idea to convert it to unified assembler syntax which has
the condition codes at the end. This would be as function more readable
considering that it might need to be extended. Missing are condition
codes, the sign extending byte/half-word loads/stores and '!'
> +
> + # 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;
> +
> + # Convert stmdb/ldmia with only one register into a plain str/ldr
> with post-increment/decrement
> + $line =~ s/^(\s*)stmdb(\s+)sp!\s*,\s*\{([^,-]+)\}/$1str$2$3, [sp,
> #-4]!/g;
> + $line =~ s/^(\s*)ldmia(\s+)sp!\s*,\s*\{([^,-]+)\}/$1ldr$2$3, [sp],
> #4/g;
> +
> + $line =~ s/\.arm/.thumb/x;
> + }
does openh264 use no conditional instructions or does armasm insert the
appropriate 'it' instructions automatically?
> +
> # comment out unsupported directives
> $line =~ s/\.type/$comm$&/x if $as_type =~ /^(apple-|armasm)/;
> $line =~ s/\.func/$comm$&/x if $as_type =~ /^(apple-|clang)/;
> --
> 1.8.1.2
>
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