Fixup continue support in while loops.

The generators were not setting `emit_continuing_` when emitting while
loops. This caused a crash when a `continue` was encountered. This CL
adds the `emit_continuing_` setup to the while emission. It also guards
the `emit_continuing_` usage with making sure the function is setup.

Bug: tint:1490
Change-Id: Ia89c49e567acda71a1f851a582103723cff71d49
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/93960
Commit-Queue: Dan Sinclair <dsinclair@chromium.org>
Auto-Submit: Dan Sinclair <dsinclair@chromium.org>
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>

src/tint/writer/glsl/generator_impl.cc

@@ -1753,7 +1753,7 @@ bool GeneratorImpl::EmitCase(const ast::CaseStatement* stmt) {
 }
 
 bool GeneratorImpl::EmitContinue(const ast::ContinueStatement*) {
-    if (!emit_continuing_()) {
+    if (!emit_continuing_ || !emit_continuing_()) {
         return false;
     }
     line() << "continue;";
@@ -2534,6 +2534,9 @@ bool GeneratorImpl::EmitWhile(const ast::WhileStatement* stmt) {
         }
     }
 
+    auto emit_continuing = [&]() { return true; };
+    TINT_SCOPED_ASSIGNMENT(emit_continuing_, emit_continuing);
+
     // If the whilehas a multi-statement conditional, then we cannot emit this
     // as a regular while in GLSL. Instead we need to generate a `while(true)` loop.
     bool emit_as_loop = cond_pre.lines.size() > 0;

src/tint/writer/glsl/generator_impl_loop_test.cc

@@ -400,6 +400,25 @@ TEST_F(GlslGeneratorImplTest_Loop, Emit_While) {
 )");
 }
 
+TEST_F(GlslGeneratorImplTest_Loop, Emit_While_WithContinue) {
+    // while(true) {
+    //   continue;
+    // }
+
+    auto* f = While(Expr(true), Block(Continue()));
+    WrapInFunction(f);
+
+    GeneratorImpl& gen = Build();
+
+    gen.increment_indent();
+
+    ASSERT_TRUE(gen.EmitStatement(f)) << gen.error();
+    EXPECT_EQ(gen.result(), R"(  while(true) {
+    continue;
+  }
+)");
+}
+
 TEST_F(GlslGeneratorImplTest_Loop, Emit_WhileWithMultiStmtCond) {
     // while(true && false) {
     //   return;

src/tint/writer/hlsl/generator_impl.cc

@@ -2634,7 +2634,7 @@ bool GeneratorImpl::EmitCase(const ast::SwitchStatement* s, size_t case_idx) {
 }
 
 bool GeneratorImpl::EmitContinue(const ast::ContinueStatement*) {
-    if (!emit_continuing_()) {
+    if (!emit_continuing_ || !emit_continuing_()) {
         return false;
     }
     line() << "continue;";
@@ -3492,6 +3492,9 @@ bool GeneratorImpl::EmitWhile(const ast::WhileStatement* stmt) {
         }
     }
 
+    auto emit_continuing = [&]() { return true; };
+    TINT_SCOPED_ASSIGNMENT(emit_continuing_, emit_continuing);
+
     // If the while has a multi-statement conditional, then we cannot emit this
     // as a regular while in HLSL. Instead we need to generate a `while(true)` loop.
     bool emit_as_loop = cond_pre.lines.size() > 0;

src/tint/writer/hlsl/generator_impl_loop_test.cc

@@ -392,6 +392,25 @@ TEST_F(HlslGeneratorImplTest_Loop, Emit_While) {
 )");
 }
 
+TEST_F(HlslGeneratorImplTest_Loop, Emit_While_WithContinue) {
+    // while(true) {
+    //   continue;
+    // }
+
+    auto* f = While(Expr(true), Block(Continue()));
+    WrapInFunction(f);
+
+    GeneratorImpl& gen = Build();
+
+    gen.increment_indent();
+
+    ASSERT_TRUE(gen.EmitStatement(f)) << gen.error();
+    EXPECT_EQ(gen.result(), R"(  [loop] while(true) {
+    continue;
+  }
+)");
+}
+
 TEST_F(HlslGeneratorImplTest_Loop, Emit_WhileWithMultiStmtCond) {
     // while(true && false) {
     //   return;

src/tint/writer/msl/generator_impl.cc

@@ -1521,7 +1521,7 @@ bool GeneratorImpl::EmitCase(const ast::CaseStatement* stmt) {
 }
 
 bool GeneratorImpl::EmitContinue(const ast::ContinueStatement*) {
-    if (!emit_continuing_()) {
+    if (!emit_continuing_ || !emit_continuing_()) {
         return false;
     }
 
@@ -2136,6 +2136,9 @@ bool GeneratorImpl::EmitWhile(const ast::WhileStatement* stmt) {
         }
     }
 
+    auto emit_continuing = [&]() { return true; };
+    TINT_SCOPED_ASSIGNMENT(emit_continuing_, emit_continuing);
+
     // If the while has a multi-statement conditional, then we cannot emit this
     // as a regular while in MSL. Instead we need to generate a `while(true)` loop.
     bool emit_as_loop = cond_pre.lines.size() > 0;

src/tint/writer/msl/generator_impl_loop_test.cc

@@ -363,6 +363,25 @@ TEST_F(MslGeneratorImplTest, Emit_While) {
 )");
 }
 
+TEST_F(MslGeneratorImplTest, Emit_While_WithContinue) {
+    // while(true) {
+    //   continue;
+    // }
+
+    auto* f = While(Expr(true), Block(Continue()));
+    WrapInFunction(f);
+
+    GeneratorImpl& gen = Build();
+
+    gen.increment_indent();
+
+    ASSERT_TRUE(gen.EmitStatement(f)) << gen.error();
+    EXPECT_EQ(gen.result(), R"(  while(true) {
+    continue;
+  }
+)");
+}
+
 TEST_F(MslGeneratorImplTest, Emit_WhileWithMultiCond) {
     // while(true && false) {
     //   return;

src/tint/writer/wgsl/generator_impl_loop_test.cc

@@ -217,6 +217,25 @@ TEST_F(WgslGeneratorImplTest, Emit_While) {
 )");
 }
 
+TEST_F(WgslGeneratorImplTest, Emit_While_WithContinue) {
+    // while(true) {
+    //   continue;
+    // }
+
+    auto* f = While(Expr(true), Block(Continue()));
+    WrapInFunction(f);
+
+    GeneratorImpl& gen = Build();
+
+    gen.increment_indent();
+
+    ASSERT_TRUE(gen.EmitStatement(f)) << gen.error();
+    EXPECT_EQ(gen.result(), R"(  while(true) {
+    continue;
+  }
+)");
+}
+
 TEST_F(WgslGeneratorImplTest, Emit_WhileMultiCond) {
     // while(true && false) {
     //   return;

test/tint/loops/while_with_continue.wgsl

@@ -0,0 +1,8 @@
+fn f() -> i32 {
+    var i : i32;
+    while (i < 4) {
+        i = i + 1;
+        continue;
+    }
+    return i;
+}

test/tint/loops/while_with_continue.wgsl.expected.glsl

@@ -0,0 +1,15 @@
+#version 310 es
+
+layout(local_size_x = 1, local_size_y = 1, local_size_z = 1) in;
+void unused_entry_point() {
+  return;
+}
+int f() {
+  int i = 0;
+  while((i < 4)) {
+    i = (i + 1);
+    continue;
+  }
+  return i;
+}
+

test/tint/loops/while_with_continue.wgsl.expected.hlsl

@@ -0,0 +1,13 @@
+[numthreads(1, 1, 1)]
+void unused_entry_point() {
+  return;
+}
+
+int f() {
+  int i = 0;
+  [loop] while((i < 4)) {
+    i = (i + 1);
+    continue;
+  }
+  return i;
+}

test/tint/loops/while_with_continue.wgsl.expected.msl

@@ -0,0 +1,12 @@
+#include <metal_stdlib>
+
+using namespace metal;
+int f() {
+  int i = 0;
+  while((i < 4)) {
+    i = as_type<int>((as_type<uint>(i) + as_type<uint>(1)));
+    continue;
+  }
+  return i;
+}
+

test/tint/loops/while_with_continue.wgsl.expected.spvasm

@@ -0,0 +1,51 @@
+; SPIR-V
+; Version: 1.3
+; Generator: Google Tint Compiler; 0
+; Bound: 27
+; Schema: 0
+               OpCapability Shader
+               OpMemoryModel Logical GLSL450
+               OpEntryPoint GLCompute %unused_entry_point "unused_entry_point"
+               OpExecutionMode %unused_entry_point LocalSize 1 1 1
+               OpName %unused_entry_point "unused_entry_point"
+               OpName %f "f"
+               OpName %i "i"
+       %void = OpTypeVoid
+          %1 = OpTypeFunction %void
+        %int = OpTypeInt 32 1
+          %5 = OpTypeFunction %int
+%_ptr_Function_int = OpTypePointer Function %int
+         %11 = OpConstantNull %int
+      %int_4 = OpConstant %int 4
+       %bool = OpTypeBool
+      %int_1 = OpConstant %int 1
+%unused_entry_point = OpFunction %void None %1
+          %4 = OpLabel
+               OpReturn
+               OpFunctionEnd
+          %f = OpFunction %int None %5
+          %8 = OpLabel
+          %i = OpVariable %_ptr_Function_int Function %11
+               OpBranch %12
+         %12 = OpLabel
+               OpLoopMerge %13 %14 None
+               OpBranch %15
+         %15 = OpLabel
+         %17 = OpLoad %int %i
+         %19 = OpSLessThan %bool %17 %int_4
+         %16 = OpLogicalNot %bool %19
+               OpSelectionMerge %21 None
+               OpBranchConditional %16 %22 %21
+         %22 = OpLabel
+               OpBranch %13
+         %21 = OpLabel
+         %23 = OpLoad %int %i
+         %25 = OpIAdd %int %23 %int_1
+               OpStore %i %25
+               OpBranch %14
+         %14 = OpLabel
+               OpBranch %12
+         %13 = OpLabel
+         %26 = OpLoad %int %i
+               OpReturnValue %26
+               OpFunctionEnd

test/tint/loops/while_with_continue.wgsl.expected.wgsl

@@ -0,0 +1,8 @@
+fn f() -> i32 {
+  var i : i32;
+  while((i < 4)) {
+    i = (i + 1);
+    continue;
+  }
+  return i;
+}