skia2/tests/sksl/shared/StaticSwitchWithBreak.asm.frag
John Stiles ffc9dec755 Eliminate redundant loads following stores.
We now have two functions `writeOpLoad` and `writeOpStore` which are
in charge of writing SpvOpLoad and SpvOpStore instructions.
`writeOpStore` also keeps track of pointer stores in a "store cache."
Subsequent loads from that same pointer will be found in the cache and
will return the value stored in that pointer instead.

Such a cache definitely cannot work in the face of control flow, so we
make the following concessions:
- `pruneReachableOps` is now `pruneConditionalOps`. Any pointers that
  are altered inside a potentially-unreachable block are cleared from
  the cache entirely.
- The entire store cache is cleared at all OpLabels within a loop.

The cache also cannot work in the presence of swizzled stores, so we
make another significant concession:
- The entire store cache is cleared whenever we store into a non-memory
  pointer (e.g., assigning into a swizzled LValue, such as `foo.xz`).

Despite these significant limitations, this manages to dramatically
shrink many real-world examples.

Change-Id: I0981a0cf7b45b064e153e9ada271494c8e00cad5
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/530054
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
2022-04-18 14:57:48 +00:00

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1.1 KiB
JavaScript

OpCapability Shader
%1 = OpExtInstImport "GLSL.std.450"
OpMemoryModel Logical GLSL450
OpEntryPoint Fragment %main "main" %sk_FragColor %sk_Clockwise
OpExecutionMode %main OriginUpperLeft
OpName %sk_FragColor "sk_FragColor"
OpName %sk_Clockwise "sk_Clockwise"
OpName %main "main"
OpName %x "x"
OpDecorate %sk_FragColor RelaxedPrecision
OpDecorate %sk_FragColor Location 0
OpDecorate %sk_FragColor Index 0
OpDecorate %sk_Clockwise BuiltIn FrontFacing
%float = OpTypeFloat 32
%v4float = OpTypeVector %float 4
%_ptr_Output_v4float = OpTypePointer Output %v4float
%sk_FragColor = OpVariable %_ptr_Output_v4float Output
%bool = OpTypeBool
%_ptr_Input_bool = OpTypePointer Input %bool
%sk_Clockwise = OpVariable %_ptr_Input_bool Input
%void = OpTypeVoid
%11 = OpTypeFunction %void
%_ptr_Function_float = OpTypePointer Function %float
%float_0 = OpConstant %float 0
%16 = OpConstantComposite %v4float %float_0 %float_0 %float_0 %float_0
%main = OpFunction %void None %11
%12 = OpLabel
%x = OpVariable %_ptr_Function_float Function
OpStore %x %float_0
OpStore %x %float_0
OpStore %sk_FragColor %16
OpReturn
OpFunctionEnd