Fix dangling phi bug from loop-unroll (#4239)
Fix dangling phi bug from loop-unroll When unrolling the following loop: ``` %const0 = OpConstant ... %const1 = OpConstant ... ... %LoopHeader = OpLabel %phi0 = OpPhi %float %const0 %PreHeader %phi1 %Latch %phi1 = OpPhi %float %const1 %PreHeader %x %Latch ... %LoopBody = OpLabel %x = OpFSub %float %phi1 %phi0 ... ``` the loop-unroll pass sets the value of `%phi0` as `%phi1` for the second copy of the loop body. For example, the second copy of `%x = OpFSub %float %phi1 %phi0` will be `%y = OpFSub %float %x %phi1`. Since all phi instructions for inductions will are removed after the loop unrolling, `%phi1` will be a dead dangling phi. It happens only for the phi values of the first loop iteration. Replacing those dangling phis with their initial values fixes this issue. For example, the second copy of `%x = OpFSub %float %phi1 %phi0` should be `%y = OpFSub %float %x %const1` because the value of `%phi1` from the first loop iteration is `%const1`.
This commit is contained in:
Jaebaek Seo
GitHub
Родитель
07ec4f83c5
Коммит
089d716d25
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@ -797,6 +797,9 @@ void LoopUnrollerUtilsImpl::CloseUnrolledLoop(Loop* loop) {
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for (BasicBlock* block : loop_blocks_inorder_) {
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RemapOperands(block);
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}
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for (auto& block_itr : blocks_to_add_) {
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RemapOperands(block_itr.get());
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}
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// Rewrite the last phis, since they may still reference the original phi.
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for (Instruction* last_phi : state_.previous_phis_) {
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@ -3401,6 +3401,215 @@ OpFunctionEnd
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SinglePassRunAndCheck<LoopUnroller>(shader, output, false);
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}
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TEST_F(PassClassTest, UnrollWithPhiReferencesPhi) {
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const std::string text = R"(
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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" %color
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OpExecutionMode %main OriginUpperLeft
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OpSource HLSL 600
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OpName %main "main"
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OpName %color "color"
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OpDecorate %color Location 0
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%uint = OpTypeInt 32 0
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%float = OpTypeFloat 32
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%float_0 = OpConstant %float 0
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%float_1 = OpConstant %float 1
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%uint_1 = OpConstant %uint 1
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%uint_3 = OpConstant %uint 3
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%void = OpTypeVoid
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%11 = OpTypeFunction %void
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%bool = OpTypeBool
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%v4float = OpTypeVector %float 4
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%_ptr_Output_v4float = OpTypePointer Output %v4float
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%color = OpVariable %_ptr_Output_v4float Output
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%main = OpFunction %void None %11
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%15 = OpLabel
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OpBranch %16
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%16 = OpLabel
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%17 = OpPhi %float %float_0 %15 %18 %19
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%18 = OpPhi %float %float_1 %15 %20 %19
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%21 = OpPhi %uint %uint_1 %15 %22 %19
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%23 = OpULessThanEqual %bool %21 %uint_3
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OpLoopMerge %24 %19 Unroll
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OpBranchConditional %23 %25 %24
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%25 = OpLabel
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; First loop iteration
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; CHECK: [[next_phi1_0:%\w+]] = OpFSub %float %float_1 %float_0
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; Second loop iteration
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; CHECK: [[next_phi1_1:%\w+]] = OpFSub %float [[next_phi1_0]] %float_1
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; Third loop iteration
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; CHECK: OpFSub %float [[next_phi1_1]] [[next_phi1_0]]
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%20 = OpFSub %float %18 %17
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OpBranch %19
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%19 = OpLabel
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%22 = OpIAdd %uint %21 %uint_1
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OpBranch %16
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%24 = OpLabel
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OpReturn
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OpFunctionEnd
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)";
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std::unique_ptr<IRContext> context =
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BuildModule(SPV_ENV_UNIVERSAL_1_1, nullptr, text,
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SPV_TEXT_TO_BINARY_OPTION_PRESERVE_NUMERIC_IDS);
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Module* module = context->module();
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EXPECT_NE(nullptr, module) << "Assembling failed for ushader:\n"
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<< text << std::endl;
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LoopUnroller loop_unroller;
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SetDisassembleOptions(SPV_BINARY_TO_TEXT_OPTION_NO_HEADER |
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SPV_BINARY_TO_TEXT_OPTION_FRIENDLY_NAMES);
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SinglePassRunAndMatch<LoopUnroller>(text, true);
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}
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TEST_F(PassClassTest, UnrollWithDoublePhiReferencesPhi) {
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const std::string text = R"(
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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" %color
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OpExecutionMode %main OriginUpperLeft
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OpSource HLSL 600
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OpName %main "main"
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OpName %color "color"
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OpDecorate %color Location 0
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%uint = OpTypeInt 32 0
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%float = OpTypeFloat 32
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%float_0 = OpConstant %float 0
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%float_1 = OpConstant %float 1
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%uint_1 = OpConstant %uint 1
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%uint_3 = OpConstant %uint 3
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%void = OpTypeVoid
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%11 = OpTypeFunction %void
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%bool = OpTypeBool
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%v4float = OpTypeVector %float 4
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%_ptr_Output_v4float = OpTypePointer Output %v4float
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%color = OpVariable %_ptr_Output_v4float Output
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%main = OpFunction %void None %11
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%15 = OpLabel
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OpBranch %16
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%16 = OpLabel
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%17 = OpPhi %float %float_1 %15 %18 %19
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%18 = OpPhi %float %float_0 %15 %20 %19
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%20 = OpPhi %float %float_1 %15 %21 %19
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%22 = OpPhi %uint %uint_1 %15 %23 %19
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%24 = OpULessThanEqual %bool %22 %uint_3
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OpLoopMerge %25 %19 Unroll
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OpBranchConditional %24 %26 %25
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%26 = OpLabel
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; First loop iteration
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; CHECK: [[next_phi1_0:%\w+]] = OpFSub %float %float_1 %float_0
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; CHECK: OpFMul %float %float_1
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; Second loop iteration
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; CHECK: [[next_phi1_1:%\w+]] = OpFSub %float [[next_phi1_0]] %float_1
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; CHECK: OpFMul %float %float_0
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; Third loop iteration
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; CHECK: OpFSub %float [[next_phi1_1]] [[next_phi1_0]]
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; CHECK: OpFMul %float %float_1
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%21 = OpFSub %float %20 %18
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%27 = OpFMul %float %17 %21
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OpBranch %19
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%19 = OpLabel
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%23 = OpIAdd %uint %22 %uint_1
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OpBranch %16
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%25 = OpLabel
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OpReturn
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OpFunctionEnd
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)";
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std::unique_ptr<IRContext> context =
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BuildModule(SPV_ENV_UNIVERSAL_1_1, nullptr, text,
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SPV_TEXT_TO_BINARY_OPTION_PRESERVE_NUMERIC_IDS);
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Module* module = context->module();
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EXPECT_NE(nullptr, module) << "Assembling failed for ushader:\n"
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<< text << std::endl;
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LoopUnroller loop_unroller;
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SetDisassembleOptions(SPV_BINARY_TO_TEXT_OPTION_NO_HEADER |
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SPV_BINARY_TO_TEXT_OPTION_FRIENDLY_NAMES);
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SinglePassRunAndMatch<LoopUnroller>(text, true);
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}
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TEST_F(PassClassTest, PartialUnrollWithPhiReferencesPhi) {
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// With LocalMultiStoreElimPass
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const std::string text = R"(
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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" %color
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OpExecutionMode %main OriginUpperLeft
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OpSource HLSL 600
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OpName %main "main"
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OpName %color "color"
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OpDecorate %color Location 0
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%uint = OpTypeInt 32 0
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%float = OpTypeFloat 32
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%float_0 = OpConstant %float 0
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%float_1 = OpConstant %float 1
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%uint_1 = OpConstant %uint 1
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%uint_3 = OpConstant %uint 3
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%void = OpTypeVoid
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%11 = OpTypeFunction %void
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%bool = OpTypeBool
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%v4float = OpTypeVector %float 4
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%_ptr_Output_v4float = OpTypePointer Output %v4float
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%color = OpVariable %_ptr_Output_v4float Output
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%main = OpFunction %void None %11
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%15 = OpLabel
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OpBranch %16
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%16 = OpLabel
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%17 = OpPhi %float %float_0 %15 %18 %19
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%18 = OpPhi %float %float_1 %15 %20 %19
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%21 = OpPhi %uint %uint_1 %15 %22 %19
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%23 = OpULessThanEqual %bool %21 %uint_3
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OpLoopMerge %24 %19 Unroll
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OpBranchConditional %23 %25 %24
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%25 = OpLabel
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; CHECK: [[phi0_0:%\w+]] = OpPhi {{%\w+}} {{%\w+}} {{%\w+}} [[phi1_0:%\w+]]
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; CHECK: [[phi1_0]] = OpPhi {{%\w+}} {{%\w+}} {{%\w+}} [[sub:%\w+]]
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; CHECK: [[sub]] = OpFSub {{%\w+}} [[phi1_0]] [[phi0_0]]
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; CHECK: [[phi0_1:%\w+]] = OpPhi {{%\w+}} [[phi0_0]]
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; CHECK: [[phi1_1:%\w+]] = OpPhi {{%\w+}} [[phi1_0]]
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; CHECK: [[sub:%\w+]] = OpFSub {{%\w+}} [[phi1_1]] [[phi0_1]]
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; CHECK: OpFSub {{%\w+}} [[sub]] [[phi1_1]]
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%20 = OpFSub %float %18 %17
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OpBranch %19
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%19 = OpLabel
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%22 = OpIAdd %uint %21 %uint_1
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OpBranch %16
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%24 = OpLabel
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OpReturn
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OpFunctionEnd
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)";
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std::unique_ptr<IRContext> context =
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BuildModule(SPV_ENV_UNIVERSAL_1_1, nullptr, text,
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SPV_TEXT_TO_BINARY_OPTION_PRESERVE_NUMERIC_IDS);
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Module* module = context->module();
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EXPECT_NE(nullptr, module) << "Assembling failed for ushader:\n"
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<< text << std::endl;
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LoopUnroller loop_unroller;
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SetDisassembleOptions(SPV_BINARY_TO_TEXT_OPTION_NO_HEADER);
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SinglePassRunAndMatch<PartialUnrollerTestPass<2>>(text, true);
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}
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} // namespace
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} // namespace opt
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} // namespace spvtools
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