[PATCH], Fix constraints on VSX Fma, Fix, and Reduce options

[Michael Meissner <meissner at linux dot vnet dot ibm dot com>]

In doing work on improving power8 fusion support, I noticed that in several of
the patterns (vector fused multiply-add, optimization of float (fix (x)), and
vector reduction), I used the "ws" constraint which is the constraint for
scalar double precision floating point (currently FLOAT_REGS) in cases where
the operand is a vector, where we should use "wd" (preferred constraint for
V2DF), "wf" (preferred constraint for V4SF) or even "wa" (any VSX register).
This means the register allocator might generate extra code due to preferring
the traditional floating point registers.

I was curious about the code generation changes, so I built power8 versions of
the Spec 2006 benchmark suite, and compared the number of instructions
generated, using the same options.  Most of the floating point benchmarks had
some changes in code generation, including fewer scalar floating loads/stores
(where the RA picked a traditional scalar register, which meant elsewere a
scalar was spilled to the stack), and different encodings of the FMA
instructions.

I did a run of the FP spec benchmarks on a big endian power8 system.  There
were no regressions that were significant, and the cactusADM benchmark sped up
by 2%.

I did a bootstrap/make check comparison, and there were no regressions.  Is it
ok to install in trunk and the active PowerPC branches?

-- 
Michael Meissner, IBM
IBM, M/S 2506R, 550 King Street, Littleton, MA 01460-6245, USA
email: meissner@linux.vnet.ibm.com, phone: +1 (978) 899-4797

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