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Eliminate branches with condition of OpConstantNull (#3438)

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Ehsan 2020-06-16 12:31:03 -05:00 committed by GitHub
parent 9494703546
commit a7112d544b
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2 changed files with 76 additions and 0 deletions
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1
source/opt/dead_branch_elim_pass.cpp
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@ -41,6 +41,7 @@ bool DeadBranchElimPass::GetConstCondition(uint32_t condId, bool* condVal) {
bool condIsConst;
Instruction* cInst = get_def_use_mgr()->GetDef(condId);
switch (cInst->opcode()) {
case SpvOpConstantNull:
case SpvOpConstantFalse: {
*condVal = false;
condIsConst = true;

75
test/opt/dead_branch_elim_test.cpp
View File

@ -186,6 +186,81 @@ OpFunctionEnd
true, true);
}
TEST_F(DeadBranchElimTest, IfThenElseNull) {
// For booleans OpConstantNull should be treated similar to OpConstantFalse.
//
// From the SPIR-V spec:
// OpConstantNull: Declares a new null constant value.
// The null value is type dependent, defined as follows:
// - Scalar Boolean: false
// ...
const std::string predefs =
R"(OpCapability Shader
%1 = OpExtInstImport "GLSL.std.450"
OpMemoryModel Logical GLSL450
OpEntryPoint Fragment %main "main" %gl_FragColor %BaseColor
OpExecutionMode %main OriginUpperLeft
OpSource GLSL 140
OpName %main "main"
OpName %v "v"
OpName %gl_FragColor "gl_FragColor"
OpName %BaseColor "BaseColor"
%void = OpTypeVoid
%7 = OpTypeFunction %void
%bool = OpTypeBool
%9 = OpConstantNull %bool
%float = OpTypeFloat 32
%v4float = OpTypeVector %float 4
%_ptr_Function_v4float = OpTypePointer Function %v4float
%float_0 = OpConstant %float 0
%14 = OpConstantComposite %v4float %float_0 %float_0 %float_0 %float_0
%float_1 = OpConstant %float 1
%16 = OpConstantComposite %v4float %float_1 %float_1 %float_1 %float_1
%_ptr_Output_v4float = OpTypePointer Output %v4float
%gl_FragColor = OpVariable %_ptr_Output_v4float Output
%_ptr_Input_v4float = OpTypePointer Input %v4float
%BaseColor = OpVariable %_ptr_Input_v4float Input
)";
const std::string before =
R"(%main = OpFunction %void None %7
%19 = OpLabel
%v = OpVariable %_ptr_Function_v4float Function
OpSelectionMerge %20 None
OpBranchConditional %9 %21 %22
%21 = OpLabel
OpStore %v %14
OpBranch %20
%22 = OpLabel
OpStore %v %16
OpBranch %20
%20 = OpLabel
%23 = OpLoad %v4float %v
OpStore %gl_FragColor %23
OpReturn
OpFunctionEnd
)";
const std::string after =
R"(%main = OpFunction %void None %7
%19 = OpLabel
%v = OpVariable %_ptr_Function_v4float Function
OpBranch %22
%22 = OpLabel
OpStore %v %16
OpBranch %20
%20 = OpLabel
%23 = OpLoad %v4float %v
OpStore %gl_FragColor %23
OpReturn
OpFunctionEnd
)";
SinglePassRunAndCheck<DeadBranchElimPass>(predefs + before, predefs + after,
true, true);
}
TEST_F(DeadBranchElimTest, IfThenTrue) {
// #version 140
//