77702f1704
When we determine that a function only contains a single return
statement and it is at the top level (i.e. not inside any scopes),
there is no need to create a temporary variable and store the
result expression into a variable. Instead, we can directly replace
the function-call expression with the return-statement's expression.
Unlike my previous solution, this does not require variable
declarations to be rewritten. The no-scopes limitation makes it
slightly less effective in theory, but in practice we still get
almost all of the benefit. The no-scope limitation bites us on
structures like
@if (true) {
return x;
} else {
return y;
}
Which will optimize away the if, but leave the scope:
{
return x;
}
However, this is not a big deal; the biggest wins are single-line
helper functions like `guarded_divide` and `unpremul` which retain
the full benefit.
Change-Id: I7fbb725e65db021b9795c04c816819669815578f
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/345167
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
44 lines
1.4 KiB
JavaScript
44 lines
1.4 KiB
JavaScript
OpCapability Shader
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%1 = OpExtInstImport "GLSL.std.450"
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OpMemoryModel Logical GLSL450
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OpEntryPoint Fragment %main "main" %sk_FragColor %sk_Clockwise %src %dst
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OpExecutionMode %main OriginUpperLeft
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OpName %sk_FragColor "sk_FragColor"
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OpName %sk_Clockwise "sk_Clockwise"
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OpName %src "src"
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OpName %dst "dst"
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OpName %main "main"
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OpDecorate %sk_FragColor RelaxedPrecision
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OpDecorate %sk_FragColor Location 0
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OpDecorate %sk_FragColor Index 0
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OpDecorate %sk_Clockwise RelaxedPrecision
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OpDecorate %sk_Clockwise BuiltIn FrontFacing
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OpDecorate %src RelaxedPrecision
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OpDecorate %dst RelaxedPrecision
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OpDecorate %17 RelaxedPrecision
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OpDecorate %19 RelaxedPrecision
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OpDecorate %20 RelaxedPrecision
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%float = OpTypeFloat 32
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%v4float = OpTypeVector %float 4
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%_ptr_Output_v4float = OpTypePointer Output %v4float
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%sk_FragColor = OpVariable %_ptr_Output_v4float Output
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%bool = OpTypeBool
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%_ptr_Input_bool = OpTypePointer Input %bool
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%sk_Clockwise = OpVariable %_ptr_Input_bool Input
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%_ptr_Input_v4float = OpTypePointer Input %v4float
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%src = OpVariable %_ptr_Input_v4float Input
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%dst = OpVariable %_ptr_Input_v4float Input
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%void = OpTypeVoid
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%14 = OpTypeFunction %void
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%float_1 = OpConstant %float 1
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%main = OpFunction %void None %14
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%15 = OpLabel
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%17 = OpLoad %v4float %dst
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%18 = OpCompositeExtract %float %17 3
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%19 = OpFSub %float %float_1 %18
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%20 = OpLoad %v4float %src
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%21 = OpVectorTimesScalar %v4float %20 %19
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OpStore %sk_FragColor %21
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OpReturn
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OpFunctionEnd
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