HLSL backend: work around FXC ignoring switch with only default case
In HLSL code, if a switch statement has only a default case, FXC will effectively ignore the code in that case. In this change, we detect this and work around it by emitting the code in the default block without the switch. Bug: tint:1188 Change-Id: I69b405cdb4c669fb093eb49aa138923419dcf8f8 Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/68440 Kokoro: Antonio Maiorano <amaiorano@google.com> Commit-Queue: Antonio Maiorano <amaiorano@google.com> Reviewed-by: Ben Clayton <bclayton@chromium.org>
This commit is contained in:
Antonio Maiorano
Tint LUCI CQ
parent
189dc7d3fd
commit
02acf59184
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@ -2948,7 +2948,44 @@ bool GeneratorImpl::EmitStatement(const ast::Statement* stmt) {
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return false;
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}
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bool GeneratorImpl::EmitDefaultOnlySwitch(const ast::SwitchStatement* stmt) {
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TINT_ASSERT(Writer, stmt->body.size() == 1 && stmt->body[0]->IsDefault());
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// FXC fails to compile a switch with just a default case, ignoring the
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// default case body. We work around this here by emitting the default case
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// without the switch.
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// Emit the switch condition as-is in case it has side-effects (e.g.
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// function call). Note that's it's fine not to assign the result of the
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// expression.
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{
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auto out = line();
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if (!EmitExpression(out, stmt->condition)) {
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return false;
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}
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out << ";";
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}
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// Emit "do { <default case body> } while(false);". We use a 'do' loop so
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// that break statements work as expected, and make it 'while (false)' in
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// case there isn't a break statement.
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line() << "do {";
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{
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ScopedIndent si(this);
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if (!EmitStatements(stmt->body[0]->body->statements)) {
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return false;
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}
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}
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line() << "} while (false);";
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return true;
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}
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bool GeneratorImpl::EmitSwitch(const ast::SwitchStatement* stmt) {
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// BUG(crbug.com/tint/1188): work around default-only switches
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if (stmt->body.size() == 1 && stmt->body[0]->IsDefault()) {
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return EmitDefaultOnlySwitch(stmt);
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}
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{ // switch(expr) {
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auto out = line();
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out << "switch(";
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@ -327,6 +327,10 @@ class GeneratorImpl : public TextGenerator {
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/// @param stmt the statement to emit
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/// @returns true if the statement was emitted
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bool EmitSwitch(const ast::SwitchStatement* stmt);
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// Handles generating a switch statement with only a default case
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/// @param stmt the statement to emit
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/// @returns true if the statement was emitted
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bool EmitDefaultOnlySwitch(const ast::SwitchStatement* stmt);
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/// Handles generating type
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/// @param out the output stream
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/// @param type the type to generate
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@ -23,23 +23,10 @@ using HlslGeneratorImplTest_Switch = TestHelper;
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TEST_F(HlslGeneratorImplTest_Switch, Emit_Switch) {
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Global("cond", ty.i32(), ast::StorageClass::kPrivate);
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auto* def_body = Block(create<ast::BreakStatement>());
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auto* def = create<ast::CaseStatement>(ast::CaseSelectorList{}, def_body);
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ast::CaseSelectorList case_val;
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case_val.push_back(Literal(5));
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auto* case_body = Block(create<ast::BreakStatement>());
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auto* case_stmt = create<ast::CaseStatement>(case_val, case_body);
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ast::CaseStatementList body;
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body.push_back(case_stmt);
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body.push_back(def);
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auto* cond = Expr("cond");
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auto* s = create<ast::SwitchStatement>(cond, body);
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auto* s = Switch( //
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Expr("cond"), //
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Case(Literal(5), Block(Break())), //
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DefaultCase());
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WrapInFunction(s);
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GeneratorImpl& gen = Build();
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@ -58,6 +45,26 @@ TEST_F(HlslGeneratorImplTest_Switch, Emit_Switch) {
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)");
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}
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TEST_F(HlslGeneratorImplTest_Switch, Emit_Switch_OnlyDefaultCase) {
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Global("cond", ty.i32(), ast::StorageClass::kPrivate);
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Global("a", ty.i32(), ast::StorageClass::kPrivate);
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auto* s = Switch( //
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Expr("cond"), //
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DefaultCase(Block(Assign(Expr("a"), Expr(42)))));
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WrapInFunction(s);
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GeneratorImpl& gen = Build();
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gen.increment_indent();
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ASSERT_TRUE(gen.EmitStatement(s)) << gen.error();
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EXPECT_EQ(gen.result(), R"( cond;
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do {
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a = 42;
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} while (false);
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)");
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}
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} // namespace
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} // namespace hlsl
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} // namespace writer
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@ -0,0 +1,20 @@
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[[stage(compute), workgroup_size(1)]]
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fn f() {
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var i : i32;
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var result : i32;
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switch(i) {
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case 0: {
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result = 10;
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}
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case 1: {
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result = 22;
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}
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case 2: {
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result = 33;
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}
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default: {
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result = 44;
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break;
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}
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}
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}
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@ -0,0 +1,24 @@
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[numthreads(1, 1, 1)]
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void f() {
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int i = 0;
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int result = 0;
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switch(i) {
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case 0: {
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result = 10;
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break;
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}
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case 1: {
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result = 22;
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break;
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}
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case 2: {
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result = 33;
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break;
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}
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default: {
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result = 44;
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break;
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}
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}
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return;
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}
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@ -0,0 +1,27 @@
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#include <metal_stdlib>
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using namespace metal;
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kernel void f() {
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int i = 0;
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int result = 0;
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switch(i) {
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case 0: {
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result = 10;
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break;
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}
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case 1: {
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result = 22;
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break;
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}
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case 2: {
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result = 33;
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break;
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}
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default: {
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result = 44;
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break;
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}
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}
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return;
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}
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@ -0,0 +1,43 @@
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; SPIR-V
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; Version: 1.3
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; Generator: Google Tint Compiler; 0
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; Bound: 20
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; Schema: 0
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OpCapability Shader
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OpMemoryModel Logical GLSL450
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OpEntryPoint GLCompute %f "f"
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OpExecutionMode %f LocalSize 1 1 1
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OpName %f "f"
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OpName %i "i"
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OpName %result "result"
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%void = OpTypeVoid
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%1 = OpTypeFunction %void
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%int = OpTypeInt 32 1
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%_ptr_Function_int = OpTypePointer Function %int
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%8 = OpConstantNull %int
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%int_10 = OpConstant %int 10
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%int_22 = OpConstant %int 22
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%int_33 = OpConstant %int 33
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%int_44 = OpConstant %int 44
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%f = OpFunction %void None %1
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%4 = OpLabel
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%i = OpVariable %_ptr_Function_int Function %8
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%result = OpVariable %_ptr_Function_int Function %8
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%11 = OpLoad %int %i
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OpSelectionMerge %10 None
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OpSwitch %11 %12 0 %13 1 %14 2 %15
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%13 = OpLabel
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OpStore %result %int_10
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OpBranch %10
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%14 = OpLabel
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OpStore %result %int_22
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OpBranch %10
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%15 = OpLabel
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OpStore %result %int_33
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OpBranch %10
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%12 = OpLabel
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OpStore %result %int_44
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OpBranch %10
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%10 = OpLabel
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OpReturn
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OpFunctionEnd
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@ -0,0 +1,20 @@
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[[stage(compute), workgroup_size(1)]]
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fn f() {
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var i : i32;
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var result : i32;
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switch(i) {
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case 0: {
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result = 10;
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}
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case 1: {
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result = 22;
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}
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case 2: {
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result = 33;
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}
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default: {
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result = 44;
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break;
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}
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}
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}
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@ -0,0 +1,11 @@
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[[stage(compute), workgroup_size(1)]]
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fn f() {
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var i : i32;
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var result : i32;
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switch(i) {
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default: {
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result = 44;
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break;
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}
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}
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}
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@ -0,0 +1,11 @@
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[numthreads(1, 1, 1)]
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void f() {
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int i = 0;
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int result = 0;
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i;
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do {
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result = 44;
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break;
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} while (false);
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return;
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}
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@ -0,0 +1,15 @@
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#include <metal_stdlib>
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using namespace metal;
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kernel void f() {
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int i = 0;
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int result = 0;
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switch(i) {
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default: {
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result = 44;
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break;
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}
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}
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return;
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}
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@ -0,0 +1,31 @@
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; SPIR-V
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; Version: 1.3
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; Generator: Google Tint Compiler; 0
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; Bound: 14
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; Schema: 0
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OpCapability Shader
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OpMemoryModel Logical GLSL450
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OpEntryPoint GLCompute %f "f"
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OpExecutionMode %f LocalSize 1 1 1
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OpName %f "f"
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OpName %i "i"
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OpName %result "result"
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%void = OpTypeVoid
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%1 = OpTypeFunction %void
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%int = OpTypeInt 32 1
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%_ptr_Function_int = OpTypePointer Function %int
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%8 = OpConstantNull %int
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%int_44 = OpConstant %int 44
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%f = OpFunction %void None %1
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%4 = OpLabel
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%i = OpVariable %_ptr_Function_int Function %8
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%result = OpVariable %_ptr_Function_int Function %8
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%11 = OpLoad %int %i
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OpSelectionMerge %10 None
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OpSwitch %11 %12
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%12 = OpLabel
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OpStore %result %int_44
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OpBranch %10
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%10 = OpLabel
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OpReturn
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OpFunctionEnd
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@ -0,0 +1,11 @@
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[[stage(compute), workgroup_size(1)]]
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fn f() {
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var i : i32;
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var result : i32;
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switch(i) {
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default: {
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result = 44;
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break;
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}
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}
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}
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