[PATCH 4/4][AArch64] Cost CCMP instruction sequences to choose better expand order

[James Greenhalgh]

On Thu, Jan 28, 2016 at 02:33:20PM +0000, James Greenhalgh wrote:
> On Mon, Jan 25, 2016 at 08:09:39PM +0000, Wilco Dijkstra wrote:
> > Andreas Schwab <schwab@linux-m68k.org> wrote:
> > 
> > > FAIL: gcc.target/aarch64/ccmp_1.c scan-assembler-times \tcmp\tw[0-9]+, 0 4
> > > FAIL: gcc.target/aarch64/ccmp_1.c scan-assembler adds\t
> > > FAIL: gcc.target/aarch64/ccmp_1.c scan-assembler-times fccmpe\t.*0\\.0 1
> > 
> > Yes I noticed those too, and here is the fix. Richard's recent change added
> > UNSPEC to the CCMP patterns to stop combine optimizing the CCMP CCmode
> > immediate in a rare case. This requires a change to the CCMP cost calculation
> > as the CCMP instruction with unspec is no longer recognized.
> > 
> > Fix the ccmp_1.c test to allow both '0' and 'wzr' on cmp - BTW is there a
> > regular expression that correctly implements (0|xzr)? If I use that the test
> > still fails somehow but \[0wzr\]+ works fine... Is the correct syntax
> > documented somewhere?
> > 
> > Finally to ensure FCCMPE is emitted on relational compares, add
> > -ffinite-math-only.
> > 
> > ChangeLog:
> > 2016-01-25  Wilco Dijkstra  <wdijkstr@arm.com>
> > 
> > gcc/
> > 	* config/aarch64/aarch64.c (aarch64_if_then_else_costs):
> > 	Remove CONST_INT_P check in CCMP cost calculation.
> > 
> > gcc/testsuite/
> > 	* gcc.target/aarch64/ccmp_1.c: Fix test issues.

I'm still seeing:

  FAIL: gcc.target/aarch64/ccmp_1.c scan-assembler-times \\tcmp\\tw[0-9]+, (0|wzr) 4

Looking at the assembly generated for me with this testcase I see ccmp
with zero in 5 places:

  f3:
	cmp	w1, 34
	ccmp	w0, 19, 0, eq
	cset	w0, eq
	ret
  f4:
	cmp	w0, 35
	ccmp	w1, 20, 0, eq
	cset	w0, eq
	ret

  f7:
	cmp	w0, 0
	ccmp	w1, 7, 0, eq
	cset	w0, eq
	ret

  f8:
	cmp	w1, 0
	ccmp	w0, 9, 0, eq
	cset	w0, eq
	ret

  f11:
	fcmpe	d0, #0.0
	ccmp	w0, 30, 0, mi
	cset	w0, eq
	ret

Are these all expected? If so, can you spin the "obvious" patch to bump
this number to 5.

Thanks,
James