skia2/resources/sksl/inliner/InlinerHonorsGLSLOutParamSemantics.sksl
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

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245 B
Plaintext

uniform half4 colorGreen, colorRed;
bool out_params_are_distinct(out half x, out half y) {
x = 1;
y = 2;
return x == 1 && y == 2;
}
half4 main() {
half x = 0;
return out_params_are_distinct(x, x) ? colorGreen : colorRed;
}