Use add for a = a + b and a = b + a when possible.

Use add for a = a + b and a = b + a when possible.

Since except for Bonnell,

01 fb                   add    %edi,%ebx

is faster and shorter than

8d 1c 1f                lea    (%rdi,%rbx,1),%ebx

we should use add for a = a + b and a = b + a when possible if not
optimizing for Bonnell.

Tested on x86-64.

2019-12-17  H.J. Lu  <hjl.tools@gmail.com>

gcc/

	PR target/92807
	* config/i386/i386.c (ix86_lea_outperforms): Check !TARGET_BONNELL.
	(ix86_avoid_lea_for_addr): When not optimizing for Bonnell, use add
	for a = a + b and a = b + a.

gcc/testsuite/

	PR target/92807
	* gcc.target/i386/pr92807-1.c: New test.

From-SVN: r279451