skia2/tests/sksl/shared/Control.sksl
John Stiles 986c7fb8ca Fix codegen errors with Metal return statements.
The Metal return type from main() diverges from the SkSL source, so we
patch it in the Metal code generator. This CL improves the patching
process in multiple ways:

- A `return` statement from a fragment processor main() is rewritten to:
    return *_out;

- A `return` statement from a vertex processor main() is rewritten to:
    return (_out->sk_Position.y = -_out->sk_Position.y, *_out);

- We avoid emitting a duplicate `return *_out;` statement if we can
  determine that main() already ends in a return statement. This is
  harmless either way so it doesn't necessarily catch everything. (e.g.
  it doesn't detect an if/else which returns at the end of both blocks.)

Also added a unit test which returns from the middle of a vertex shader,
since we didn't test this anywhere and we need to verify that
sk_Position.y will be negated. (This didn't work properly before.)

Change-Id: I14cf18375894fc712fa6c6466df3888ebaeba7c8
Bug: skia:10903
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/339636
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
2020-12-01 21:28:05 +00:00

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void main() {
if (sqrt(2) > 5) { sk_FragColor = half4(0.75); } else { discard; }
int i = 0;
while (i < 10) { sk_FragColor *= 0.5; i++; }
do { sk_FragColor += 0.25; } while (sk_FragColor.x < 0.75);
for (int i = 0; i < 10; i++) {
if (i % 2 == 1) break;
else if (i > 100) return;
else continue;
}
return;
}