Add support in SILLoop::canDuplicate for PartialApplyInst.

[atrick]

Which may also generate stack allocations.

[atrick]

@swift-ci test

[atrick]

@swift-ci benchmark

[aschwaighofer]

LGTM

[swift-ci]

Performance: -O

Improvement	OLD	NEW	DELTA	RATIO
FlattenListFlatMap	5008	4338	-13.4%	1.15x (?)

Code size: -O

Performance: -Osize

Improvement	OLD	NEW	DELTA	RATIO
ObjectiveCBridgeStubToArrayOfNSString2	2860	2620	-8.4%	1.09x (?)
PrefixCountableRange	14	13	-7.1%	1.08x (?)

Code size: -Osize

Performance: -Onone

Regression	OLD	NEW	DELTA	RATIO
ArrayAppendGenericStructs	630	1550	+146.0%	0.41x (?)

Code size: -swiftlibs

How to read the data

The tables contain differences in performance which are larger than 8% and differences in code size which are larger than 1%.

If you see any unexpected regressions, you should consider fixing the
regressions before you merge the PR.

Noise: Sometimes the performance results (not code size!) contain false
alarms. Unexpected regressions which are marked with '(?)' are probably noise.
If you see regressions which you cannot explain you can try to run the
benchmarks again. If regressions still show up, please consult with the
performance team (@eeckstein).

Hardware Overview

  Model Name: Mac mini
  Model Identifier: Macmini8,1
  Processor Name: Intel Core i7
  Processor Speed: 3.2 GHz
  Number of Processors: 1
  Total Number of Cores: 6
  L2 Cache (per Core): 256 KB
  L3 Cache: 12 MB
  Memory: 64 GB