shader/execution: Add 'preventValueOptimizations' case parameterization

This controls the behaviour of `f.value()`. When enabled, the value is placed into a storage buffer and loaded, preventing the compiler from seeing the constant value. When disabled, the value is simply placed into the shader as a literal.

This was previously enabled by default.

Author: ben-clayton

src/webgpu/shader/execution/flow_control/call.spec.ts

@@ -11,6 +11,7 @@ export const g = makeTestGroup(GPUTest);
 
 g.test('call_basic')
   .desc('Test that flow control enters a called function')
+  .params(u => u.combine('preventValueOptimizations', [true, false]))
   .fn(t => {
     runFlowControlTest(t, f => ({
       entrypoint: `
@@ -27,6 +28,7 @@ fn f() {
 
 g.test('call_nested')
   .desc('Test that flow control enters a nested function calls')
+  .params(u => u.combine('preventValueOptimizations', [true, false]))
   .fn(t => {
     runFlowControlTest(t, f => ({
       entrypoint: `
@@ -53,6 +55,7 @@ fn c() {
 
 g.test('call_repeated')
   .desc('Test that flow control enters a nested function calls')
+  .params(u => u.combine('preventValueOptimizations', [true, false]))
   .fn(t => {
     runFlowControlTest(t, f => ({
       entrypoint: `

src/webgpu/shader/execution/flow_control/for.spec.ts

@@ -11,6 +11,7 @@ export const g = makeTestGroup(GPUTest);
 
 g.test('for_basic')
   .desc('Test that flow control executes a for-loop body the correct number of times')
+  .params(u => u.combine('preventValueOptimizations', [true, false]))
   .fn(t => {
     runFlowControlTest(
       t,
@@ -27,6 +28,7 @@ g.test('for_basic')
 
 g.test('for_break')
   .desc('Test that flow control exits a for-loop when reaching a break statement')
+  .params(u => u.combine('preventValueOptimizations', [true, false]))
   .fn(t => {
     runFlowControlTest(
       t,
@@ -48,6 +50,7 @@ g.test('for_break')
 
 g.test('for_continue')
   .desc('Test flow control for a for-loop continue statement')
+  .params(u => u.combine('preventValueOptimizations', [true, false]))
   .fn(t => {
     runFlowControlTest(
       t,
@@ -69,6 +72,7 @@ g.test('for_continue')
 
 g.test('for_initalizer')
   .desc('Test flow control for a for-loop initializer')
+  .params(u => u.combine('preventValueOptimizations', [true, false]))
   .fn(t => {
     runFlowControlTest(t, f => ({
       entrypoint: `
@@ -79,7 +83,7 @@ g.test('for_initalizer')
   ${f.expect_order(5)}
 `,
       extra: `
-fn initializer() -> u32 {
+fn initializer() -> i32 {
   ${f.expect_order(1)}
   return ${f.value(0)};
 }
@@ -89,6 +93,7 @@ fn initializer() -> u32 {
 
 g.test('for_condition')
   .desc('Test flow control for a for-loop condition')
+  .params(u => u.combine('preventValueOptimizations', [true, false]))
   .fn(t => {
     runFlowControlTest(t, f => ({
       entrypoint: `
@@ -99,7 +104,7 @@ g.test('for_condition')
   ${f.expect_order(8)}
 `,
       extra: `
-fn condition(i : u32) -> bool {
+fn condition(i : i32) -> bool {
   ${f.expect_order(1, 3, 5, 7)}
   return i < ${f.value(3)};
 }
@@ -109,6 +114,7 @@ fn condition(i : u32) -> bool {
 
 g.test('for_continuing')
   .desc('Test flow control for a for-loop continuing statement')
+  .params(u => u.combine('preventValueOptimizations', [true, false]))
   .fn(t => {
     runFlowControlTest(t, f => ({
       entrypoint: `
@@ -119,7 +125,7 @@ g.test('for_continuing')
   ${f.expect_order(7)}
 `,
       extra: `
-fn cont(i : u32) -> u32 {
+fn cont(i : i32) -> i32 {
   ${f.expect_order(2, 4, 6)}
   return i + 1;
 }

src/webgpu/shader/execution/flow_control/harness.ts

@@ -1,21 +1,41 @@
 import { Colors } from '../../../../common/util/colors.js';
 import { GPUTest } from '../../../gpu_test.js';
 
+/**
+ * Options for runFlowControlTest()
+ */
+interface FlowControlTest extends GPUTest {
+  params: {
+    /**
+     * If true, then constant values will be placed into a storage buffer,
+     * preventing the shader compiler from knowing the value at compile time.
+     * This can prevent constant folding, loop unrolling, dead-code
+     * optimizations etc, which would could all affect the tests.
+     */
+    preventValueOptimizations?: boolean;
+  };
+}
+
 /**
  * The builder interface for the runFlowControlTest() callback.
- * This interface is indented to be used to inject WGSL logic into the test shader.
+ * This interface is indented to be used to inject WGSL logic into the test
+ * shader.
  * @see runFlowControlTest
  */
 interface FlowControlTestBuilder {
   /**
-   * Emits an expression to load the given value from a storage buffer, preventing the shader
-   * compiler from knowing the value at compile time. This can prevent constant folding, loop
-   * unrolling, dead-code optimizations etc, which would could all affect the tests.
+   * Emits a value into the shader.
+   * If the FlowControlTest.params.preventValueOptimizations flag is enabled,
+   * then value() emits an expression to load the given value from a storage
+   * buffer, preventing the shader compiler from knowing the value at compile
+   * time. This can prevent constant folding, loop unrolling, dead-code
+   * optimizations etc, which would could all affect the tests.
    */
   value(v: number | boolean): string;
 
   /**
-   * Emits an expectation that the statement will be executed at the given chronological events.
+   * Emits an expectation that the statement will be executed at the given
+   * chronological events.
    * @param event one or more chronological events, the first being 0.
    */
   expect_order(...event: number[]): string;
@@ -55,12 +75,13 @@ interface FlowControlTestBuilder {
  * ```
  *
  * @param t The test object
- * @param builder The shader builder function that takes a FlowControlTestBuilder as the single
- * argument, and returns either a WGSL string which is embedded into the WGSL entrypoint function,
- * or a structure with entrypoint-scoped WGSL code and extra module-scope WGSL code.
+ * @param builder The shader builder function that takes a
+ * FlowControlTestBuilder as the single argument, and returns either a WGSL
+ * string which is embedded into the WGSL entrypoint function, or a structure
+ * with entrypoint-scoped WGSL code and extra module-scope WGSL code.
  */
 export function runFlowControlTest(
-  t: GPUTest,
+  t: FlowControlTest,
   build_wgsl: (builder: FlowControlTestBuilder) => string | { entrypoint: string; extra: string }
 ) {
   const inputData = new Array<number>();
@@ -80,12 +101,16 @@ export function runFlowControlTest(
 
   const build_wgsl_result = build_wgsl({
     value: v => {
-      if (typeof v === 'boolean') {
-        inputData.push(v ? 1 : 0);
-        return `inputs[${inputData.length - 1}] != 0`;
+      if (t.params.preventValueOptimizations) {
+        if (typeof v === 'boolean') {
+          inputData.push(v ? 1 : 0);
+          return `inputs[${inputData.length - 1}] != 0`;
+        }
+        inputData.push(v);
+        return `inputs[${inputData.length - 1}]`;
+      } else {
+        return `${v}`;
       }
-      inputData.push(v);
-      return `inputs[${inputData.length - 1}]`;
     },
     expect_order: (...expected) => {
       expectations.push({
@@ -117,7 +142,7 @@ struct Outputs {
   count : u32,
   data  : array<u32>,
 };
-@group(0) @binding(0) var<storage, read>       inputs  : array<u32>;
+@group(0) @binding(0) var<storage, read>       inputs  : array<i32>;
 @group(0) @binding(1) var<storage, read_write> outputs : Outputs;
 
 fn push_output(value : u32) {
@@ -142,7 +167,8 @@ ${main_wgsl.extra}
     },
   });
 
-  // If there are no inputs, just put a single value in the buffer to keep makeBufferWithContents() happy.
+  // If there are no inputs, just put a single value in the buffer to keep
+  // makeBufferWithContents() happy.
   if (inputData.length === 0) {
     inputData.push(0);
   }
@@ -191,8 +217,8 @@ ${main_wgsl.extra}
         // returns an Error with the given message and WGSL source
         const fail = (err: string) => Error(`${err}\nWGSL:\n${Colors.dim(Colors.blue(wgsl))}`);
 
-        // returns a colorized string of the expect_order() call, highlighting the event number that
-        // caused an error.
+        // returns a colorized string of the expect_order() call, highlighting
+        // the event number that caused an error.
         const expect_order_err = (expectation: ExpectedEvents, err_idx: number) => {
           let out = 'expect_order(';
           for (let i = 0; i < expectation.values.length; i++) {

src/webgpu/shader/execution/flow_control/if.spec.ts

@@ -13,6 +13,7 @@ g.test('if_true')
   .desc(
     "Test that flow control executes the 'true' block of an if statement and not the 'false' block"
   )
+  .params(u => u.combine('preventValueOptimizations', [true, false]))
   .fn(t => {
     runFlowControlTest(
       t,
@@ -32,6 +33,7 @@ g.test('if_false')
   .desc(
     "Test that flow control executes the 'false' block of an if statement and not the 'true' block"
   )
+  .params(u => u.combine('preventValueOptimizations', [true, false]))
   .fn(t => {
     runFlowControlTest(
       t,
@@ -49,6 +51,7 @@ g.test('if_false')
 
 g.test('else_if')
   .desc("Test that flow control executes the correct 'else if' block of an if statement")
+  .params(u => u.combine('preventValueOptimizations', [true, false]))
   .fn(t => {
     runFlowControlTest(
       t,

src/webgpu/shader/execution/flow_control/loop.spec.ts

@@ -11,6 +11,7 @@ export const g = makeTestGroup(GPUTest);
 
 g.test('loop_break')
   .desc('Test that flow control exits a loop when reaching a break statement')
+  .params(u => u.combine('preventValueOptimizations', [true, false]))
   .fn(t => {
     runFlowControlTest(
       t,
@@ -33,6 +34,7 @@ g.test('loop_break')
 
 g.test('loop_continue')
   .desc('Test flow control for a loop continue statement')
+  .params(u => u.combine('preventValueOptimizations', [true, false]))
   .fn(t => {
     runFlowControlTest(
       t,
@@ -60,6 +62,7 @@ g.test('loop_continue')
 
 g.test('loop_continuing_basic')
   .desc('Test basic flow control for a loop continuing block')
+  .params(u => u.combine('preventValueOptimizations', [true, false]))
   .fn(t => {
     runFlowControlTest(
       t,

src/webgpu/shader/execution/flow_control/return.spec.ts

@@ -11,6 +11,7 @@ export const g = makeTestGroup(GPUTest);
 
 g.test('return')
   .desc("Test that flow control does not execute after a 'return' statement")
+  .params(u => u.combine('preventValueOptimizations', [true, false]))
   .fn(t => {
     runFlowControlTest(
       t,
@@ -24,6 +25,7 @@ g.test('return')
 
 g.test('return_conditional_true')
   .desc("Test that flow control does not execute after a 'return' statement in a if (true) block")
+  .params(u => u.combine('preventValueOptimizations', [true, false]))
   .fn(t => {
     runFlowControlTest(
       t,
@@ -39,6 +41,7 @@ g.test('return_conditional_true')
 
 g.test('return_conditional_false')
   .desc("Test that flow control does not execute after a 'return' statement in a if (false) block")
+  .params(u => u.combine('preventValueOptimizations', [true, false]))
   .fn(t => {
     runFlowControlTest(
       t,

src/webgpu/shader/execution/flow_control/switch.spec.ts

@@ -11,6 +11,7 @@ export const g = makeTestGroup(GPUTest);
 
 g.test('switch')
   .desc('Test that flow control executes the correct switch case block')
+  .params(u => u.combine('preventValueOptimizations', [true, false]))
   .fn(t => {
     runFlowControlTest(
       t,
@@ -43,6 +44,7 @@ g.test('switch_multiple_case')
   .desc(
     'Test that flow control executes the correct switch case block with multiple cases per block'
   )
+  .params(u => u.combine('preventValueOptimizations', [true, false]))
   .fn(t => {
     runFlowControlTest(
       t,
@@ -71,6 +73,7 @@ g.test('switch_multiple_case_default')
   .desc(
     'Test that flow control executes the correct switch case block with multiple cases per block (combined with default)'
   )
+  .params(u => u.combine('preventValueOptimizations', [true, false]))
   .fn(t => {
     runFlowControlTest(
       t,
@@ -92,6 +95,7 @@ g.test('switch_multiple_case_default')
   });
 g.test('switch_default')
   .desc('Test that flow control executes the switch default block')
+  .params(u => u.combine('preventValueOptimizations', [true, false]))
   .fn(t => {
     runFlowControlTest(
       t,
@@ -122,6 +126,7 @@ ${f.expect_order(2)}
 
 g.test('switch_default_only')
   .desc('Test that flow control executes the switch default block, which is the only case')
+  .params(u => u.combine('preventValueOptimizations', [true, false]))
   .fn(t => {
     runFlowControlTest(
       t,

src/webgpu/shader/execution/flow_control/while.spec.ts

@@ -11,6 +11,7 @@ export const g = makeTestGroup(GPUTest);
 
 g.test('while_basic')
   .desc('Test that flow control executes a while-loop body the correct number of times')
+  .params(u => u.combine('preventValueOptimizations', [true, false]))
   .fn(t => {
     runFlowControlTest(
       t,
@@ -29,6 +30,7 @@ g.test('while_basic')
 
 g.test('while_break')
   .desc('Test that flow control exits a while-loop when reaching a break statement')
+  .params(u => u.combine('preventValueOptimizations', [true, false]))
   .fn(t => {
     runFlowControlTest(
       t,
@@ -52,6 +54,7 @@ g.test('while_break')
 
 g.test('while_continue')
   .desc('Test flow control for a while-loop continue statement')
+  .params(u => u.combine('preventValueOptimizations', [true, false]))
   .fn(t => {
     runFlowControlTest(
       t,