On 06/17/14 01:47, Andreas Schwab wrote:
Postreload may transform (set (REGX) (CONST_INT A)) ... (set (REGX)
(CONST_INT B)) to (set (REGX) (CONST_INT A)) ... (set (STRICT_LOW_PART
(REGX)) (CONST_INT B)), but it should do that only if the latter is
cheaper. On m68k, a full word load of a small constant with moveq is
cheaper than doing a byte load with move.b.
Tested on m68k-suse-linux and x86_64-suse-linux. In both cases the size
of cc1* becomes smaller with this change.
Andreas.
PR rtl-optimization/54555
* postreload.c (move2add_use_add2_insn): Only substitute
STRICT_LOW_PART if it is cheaper.
Sadly, Kazu didn't add a testcase for the H8/300 cases which inspired
his change, so we don't know if your patch hurts the H8/300 port or not.
Let's do better this time ;-) Add a testcase for the m68k port which
verifies we're getting the desired code. I don't care if you test the
assembly code or test the RTL dumps, just that we have a test for the
case where STRICT_LOW_PART is not a win.
With a testcase, this is approved.
Thanks,
jeff
