skia2/resources/sksl/errors/BadConstInitializers.sksl
Brian Osman 7b361499c9 Align SkSL const rules more closely with GLSL
This adds Analysis::IsConstantExpression, to determine if an expression
is a constant-expression. It now expands to cover 'const' local and
global variables, because we also enforce that the initializer on those
variables is - in turn - a constant expression.

This fixes 10837 - previously you could initialize a const variable with
a non-constant expression, and we'd emit GLSL that contained that same
pattern, which would fail to compile at the driver level. That should
not be possible any longer.

Bug: skia:10679
Bug: skia:10837
Change-Id: I517820ef4da57fff45768c0b04c55aebc18d3272
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/375856
Reviewed-by: John Stiles <johnstiles@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
2021-02-26 17:44:11 +00:00

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uniform float u;
const float c = 1;
float f = 1;
struct S { float f; } s;
// Valid constant-expression initializers. Should not produce errors:
void from_literal() { const float x = 0; }
void from_const_global() { const float x = c; }
void from_const_local() { const float x = 0; const float y = x; }
void from_const_constructor() { const int i = int(c); }
void from_expression() { const float x = 2 * c; }
// Invalid constant-expression initializers. Should all produce errors:
void from_uniform() { const float x = u; }
void from_parameter(float p) { const float x = p; }
void from_const_parameter(const float p) { const float x = p; }
void from_non_const_local() { float x = u; const float y = x; }
void from_non_const_expression() { const float x = u + u; }
void from_mixed_expression() { const float x = c + u; }
void from_non_const_struct_field() { const float x = s.f; }