skia2/resources/sksl/shared/Assignment.sksl
John Stiles f10eff363b Fix misdetection of dead global variables.
A global variable should be considered "dead" if it's never written and
never read. The previous code checked if it was never written OR never
read, which is not the same.

This would generate GLSL/Metal that didn't compile. In SPIR-V, it would
SkASSERT, then crash, during codegen. The fuzzer was able to detect the
SPIR-V issue, but it was wrong in all three cases.

Change-Id: Id59a2499eb5baa3839b93826bfbc24191bfd490b
Bug: oss-fuzz:32005
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/385280
Commit-Queue: John Stiles <johnstiles@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
2021-03-16 16:02:03 +00:00

48 lines
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uniform half4 colorGreen;
struct S {
float f;
float af[5];
half4 h4;
half4 ah4[5];
};
half4 globalVar;
S globalStruct;
half4 main() {
/* assign to scalar */ int i; i = 0;
/* assign to vector */ int4 i4; i4 = int4(1,2,3,4);
/* assign to matrix */ float3x3 f3x3; f3x3 = float3x3(1,2,3,4,5,6,7,8,9);
/* assign to swizzle */ half4 x; x.w = 0; x.yx = half2(0);
/* assign to array of scalar */ int ai[1]; ai[0] = 0;
/* assign to array of vector */ int4 ai4[1]; ai4[0] = int4(1,2,3,4);
/* assign to array of matrix */ half3x3 ah2x4[1]; ah2x4[0] = half3x3(1,2,3,4,5,6,7,8,9);
/* assign to array swizzle */ float4 af4[1]; af4[0].x = 0; af4[0].ywxz = float4(1);
/* assign to struct variable */ S s; s.f = 0;
/* assign to struct array */ s.af[1] = 0;
/* assign to struct swizzle */ s.h4.zxy = half3(9);
/* assign to struct array swizzle */ s.ah4[2].yw = half2(5);
/* assign to global var */ globalVar = half4(0);
/* assign to global struct */ globalStruct.f = 0;
// Not allowed in ES2
// /* assign to array idx by lookup */ ai[0] = 0; ai[ai[0]] = 0;
// Not allowed natively in GLSL, but SkSL will turn these into valid GLSL expressions.
/* assign to folded ternary */ half l, r; (true ? l : r) = 0;
/* assign to unary plus */ +ai[0] += +ai4[0][0];
/* assign to struct unary plus */ +s.f = 1; +s.af[0] = 2;
+s.h4 = half4(1); +s.ah4[0] = half4(2);
// Keep these variables alive
af4[0] *= float(ah2x4[0][0][0]);
i4.y *= i;
x.y *= l;
s.f *= l;
return colorGreen;
}