Generate prologue/epilogue using STRD/LDRD in ARM mode, when tuning prefer_ldrd_strd flag is set, such as in Cortex-A15.
[1/3] Prologue using STRD in ARM mode [2/3] Epilogue using LDRD in ARM mode [3/3] Adjust tests gcc.target/arm/interrupt-*.c Testing and benchmarking: * No regression on qemu for arm-none-eabi cortex-a15 neon softfp arm. * Successful bootstrap on Cortex-A15. * No change in performance for Spec2k on Cortex-A15 hardware. Ok for trunk? Thanks, Greta
