Hi all,

As part of investigating the codegen effects of a fix for PR 65932 I found we assign
too high a cost for the sign-extending multiply instruction SMULBB.
This is because we add the cost of a multiply-extend but then also recurse into the
SIGN_EXTEND sub-expressions rather than the registers (or subregs) being sign-extended.

This patch is a simple fix. The fix is right by itself, but in combination with patch 3
fix the gcc.target/arm/wmul-2.c testcase.

Bootstrapped and tested on arm-none-linux-gnueabihf.

Ok for trunk?

Thanks,
Kyrill

2016-01-22  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>

     * config/arm/arm.c (arm_new_rtx_costs, MULT case): Properly extract
     the operands of the SIGN_EXTENDs from a SMUL[TB][TB] rtx.