vc4: piglit's variable indexing tests regressed
Several of piglit tests related with variable indexing has regressed due commit 46a9df6a (part of !14573 (merged)):
- generated_tests/spec/glsl-1.10/execution/variable-indexing/fs-temp-array-mat4-index-col-row-wr.shader_test
- generated_tests/spec/glsl-1.10/execution/variable-indexing/vs-temp-array-mat4-index-col-row-wr.shader_test
- generated_tests/spec/glsl-1.20/execution/variable-indexing/fs-temp-array-mat4-index-col-wr.shader_test
- generated_tests/spec/glsl-1.20/execution/variable-indexing/fs-temp-array-mat4-index-row-wr.shader_test
- generated_tests/spec/glsl-1.20/execution/variable-indexing/fs-temp-array-mat4-index-wr.shader_test
- generated_tests/spec/glsl-1.20/execution/variable-indexing/vs-temp-array-mat4-index-col-wr.shader_test
- generated_tests/spec/glsl-1.20/execution/variable-indexing/vs-temp-array-mat4-index-row-wr.shader_test
- generated_tests/spec/glsl-1.20/execution/variable-indexing/vs-temp-array-mat4-index-wr.shader_test