Commit Graph

8 Commits

Author SHA1 Message Date
John Stiles
0c9d888748 Run SkSL inliner tests as part of dm.
Previously, these tests were never actually executed, only read during
code review. They are now properly tested for correctness whenever dm
is run. Non-ES2 compliant statements (do/while/switch) are unfortunately
excluded here, as they are not compatible with Runtime Effects yet.

Change-Id: I965c782baad6f8dd3961a400ae791fb2c1f844d3
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/389296
Auto-Submit: John Stiles <johnstiles@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
2021-03-25 22:58:54 +00:00
John Stiles
bff24abab8 Disallow inlining a function with out-parameters.
It is difficult to do this both efficiently and correctly while honoring
GLSL semantics (which require the lvalues to be kept distinct, even when
they point to the same variable). We could make it work by making copies
of every out parameter in each direction (going in for inouts, and
coming out for outs and inouts).

However, this could be self-defeating if it makes it harder for the
driver to track variable lifetimes. Simply opting out of inlining these
functions entirely seems like the best tradeoff; let the driver optimize
them if it can, and we can enjoy reduced complexity in the SkSL inliner.

Change-Id: I62f7b4550cc181cfe789e4f2ff4e408ba1baf9cb
Bug: skia:11326
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/370257
Reviewed-by: Brian Osman <brianosman@google.com>
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
2021-03-17 18:04:00 +00:00
John Stiles
dc20847579 Disallow inlining functions containing early returns.
This allows us to remove 100 LOC from the inliner and is very unlikely
to affect any existing benchmark. We don't have any evidence to support
the idea that a one-iteration `for` loop with `continue`-based exits
will be any faster than a standard function call on any existing GPU.
Our fragment processors are generally written to avoid early returns,
in large part to avoid hitting this path.

This drastically impacts BlendEnum.sksl (which can no longer flatten out
a switch over every blend function in SkSL) but is otherwise a wash.

See: http://go/optimization-in-sksl-inliner suggestion 4(a)

Change-Id: I1f9c27bcd7a8de46cc4e8d0b9768d75957cf1c50
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/385377
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
2021-03-17 16:29:00 +00:00
John Stiles
f3a28db703 Eliminate control-flow analysis.
We no longer derive a performance benefit from this pass in practice,
and it is a very expensive compilation step. It is also prone to fuzz-
related errors.

Doc: http://go/optimization-in-sksl

Change-Id: Ief08ffac659a8fe7fe92c92b9a5da14c9f713bc2
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/381261
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
2021-03-11 13:24:54 +00:00
John Stiles
0dd1a77e12 Add noinline keyword to SkSL.
As you might expect, a function tagged with `noinline` will never be
considered as a candidate for inlining.

Change-Id: Ia098f8974e6de251d78bb2a76cd71db8a86bc19c
Bug: skia:11362
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/382337
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
2021-03-10 15:39:48 +00:00
John Stiles
66c53b9428 Demonstrate a bug with inlined static switches.
When we detect a static switch, the optimizer finds the matching switch-
case and eliminates all the other switch-cases. It handles case
fall-through by scanning forward and looking for an unconditional break.

However, the inliner has an interesting quirk--it can replace `return`
statements inside of a switch with `continue` statements, since the body
of the inlined function has been wrapped with a for-loop to allow for
early exits. The optimizer does not recognize these continue statements
as exits from the switch (although they certainly qualify), so it
treats continues as fallen-through and keeps emitting switch-cases.

The dead-code elimination pass was actually doing us a favor here and
eliminating the excess code later. A flag was added to disable DCE in
order to reveal the problem in a test.

Change-Id: I8ff19fde5e32d0ab73d7c5411da40cb953a446f5
Bug: skia:11352
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/372956
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
2021-02-22 15:05:58 +00:00
John Stiles
92d83b7b9d Add test to demonstrate out-param semantics violation.
GLSL ES2 documentation on out parameters: "Evaluation of an out
parameter results in an l-value that is used to copy out a value when
the function returns."

The inliner does not do any alias checking when inlining an `out` param.
That is, passing the same variable to two separate `out` parameters
would not generate two distinct lvalues in the inlined code; it reuses
the same variable for each out-params in the inlined code.

(Amusingly, our CFG can fully optimize away this test code so it just
returns "red".)

Change-Id: Ib781d2cfdac54f01b6abe159af0c84ff24ff6976
Bug: skia:11326
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/370256
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
2021-02-16 14:28:49 +00:00
John Stiles
bfc9be0f77 Migrate SkSL test inputs to the resources/ directory.
This will allow us to load these inputs for unit testing in `dm`.

Change-Id: Id256ba7c30d3ec94b98048e47af44cf9efe580d5
Bug: skia:11009
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/357282
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
2021-01-22 18:57:29 +00:00