Like the logical operations, expand all shifts early rather than only
sometimes.  The Neon shift expansions are never emitted (not even with
-fneon-for-64bits), so they are not useful.  So all the late expansions
and Neon shift patterns can be removed, and shifts are more optimized
as a result.  Since some extend patterns use Neon DImode shifts, remove
the Neon extend variants and related splits.

A simple example now generates the same efficient code after this
patch with -mfpu=neon and -mfpu=vfp (previously just the fact of
having Neon enabled resulted inefficient code for no reason).

unsigned long long f(unsigned long long x, unsigned long long y)
{ return x & (y >> 33); }

Before:
	strd    r4, r5, [sp, #-8]!
	lsr     r4, r3, #1
	mov     r5, #0
	and     r1, r1, r5
	and     r0, r0, r4
	ldrd    r4, r5, [sp]
	add     sp, sp, #8
	bx      lr

After:
	and     r0, r0, r3, lsr #1
	mov     r1, #0
	bx      lr

Bootstrap and regress OK on arm-none-linux-gnueabihf --with-cpu=cortex-a57

    gcc/
	* config/arm/iterators.md (qhs_extenddi_cstr): Update.
	(qhs_extenddi_cstr): Likewise.
	* config/arm/arm.md (ashldi3): Always expand early.
	(ashlsi3): Likewise.
	(ashrsi3): Likewise.
	(zero_extend<mode>di2): Remove Neon variants.
	(extend<mode>di2): Likewise.
	* config/arm/neon.md (ashldi3_neon_noclobber): Remove.
	(signed_shift_di3_neon): Likewise.
	(unsigned_shift_di3_neon): Likewise.
	(ashrdi3_neon_imm_noclobber): Likewise.
	(lshrdi3_neon_imm_noclobber): Likewise.
	(<shift>di3_neon): Likewise.
	(split extend): Remove DI extend split patterns.

   gcc/testsuite/
	* gcc.target/arm/neon-extend-1.c: Remove test.
	* gcc.target/arm/neon-extend-2.c: Remove test.

From-SVN: r274824