[x264-devel] [PATCH 11/14] gas-preprocessor: Convert ldr with a too large shift into add+ldr for thumb

[Martin Storsjö]

This only works in the special case when the base register is the
same as the target for the ldr.
---
 tools/gas-preprocessor.pl | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/tools/gas-preprocessor.pl b/tools/gas-preprocessor.pl
index 4c2cf9d..afdfc9e 100755
--- a/tools/gas-preprocessor.pl
+++ b/tools/gas-preprocessor.pl
@@ -957,6 +957,14 @@ sub handle_serialized_line {
         # Convert "and r0, sp, #xx" into "mov r0, sp", "and r0, r0, #xx"
         $line =~ s/and\s+(\w+),\s*(sp|r13)\,\s*#(\w+)/mov $1, $2\n\tand $1, $1, #$3/g;
 
+        # Convert "ldr r0, [r0, r1, lsl #6]" where the shift is >3 (which
+        # can't be handled in thumb) into "add r0, r0, r1, lsl #6",
+        # "ldr r0, [r0]", for the special case where the same address is
+        # used as base and target for the ldr.
+        if ($line =~ /(ldr[bh]?)\s+(\w+),\s*\[\2,\s*(\w+),\s*lsl\s*#(\w+)\]/ and $4 > 3) {
+            $line =~ s/(ldr[bh]?)\s+(\w+),\s*\[\2,\s*(\w+),\s*lsl\s*#(\w+)\]/add $2, $2, $3, lsl #$4\n\t$1 $2, [$2]/;
+        }
+
         $line =~ s/\.arm/.thumb/x;
     }
 
-- 
2.7.4