Statically eliminate unnecessary branches in generic contexts

In order to use the new compile time type checks in generics, untaken branches must be skipped because these might be invalid.

src/compiler.ts

@@ -1331,19 +1331,21 @@ export class Compiler extends DiagnosticEmitter {
     flow.continueLabel = previousContinueLabel;
 
     var module = this.module;
-    var condition = makeIsTrueish(
+    var condExpr = makeIsTrueish(
       this.compileExpression(statement.condition, Type.i32, ConversionKind.NONE),
       this.currentType,
       module
     );
 
+    // No need to eliminate the condition in generic contexts as the statement is executed anyway.
+
     this.currentFunction.leaveBreakContext();
 
     return module.createBlock(breakLabel, [
       module.createLoop(continueLabel,
         module.createBlock(null, [
           body,
-          module.createBreak(continueLabel, condition)
+          module.createBreak(continueLabel, condExpr)
         ], NativeType.None))
     ], NativeType.None);
   }
@@ -1418,26 +1420,44 @@ export class Compiler extends DiagnosticEmitter {
 
   compileIfStatement(statement: IfStatement): ExpressionRef {
     var module = this.module;
+    var currentFunction = this.currentFunction;
+    var ifTrue = statement.ifTrue;
+    var ifFalse = statement.ifFalse;
 
     // The condition doesn't initiate a branch yet
-    var condition = makeIsTrueish(
+    var condExpr = makeIsTrueish(
       this.compileExpression(statement.condition, Type.i32, ConversionKind.NONE),
       this.currentType,
       module
     );
 
+    // Eliminate unnecesssary branches in generic contexts if the condition is constant
+    if (
+      this.currentFunction.isAny(CommonFlags.GENERIC | CommonFlags.GENERIC_CONTEXT) &&
+      _BinaryenExpressionGetId(condExpr = this.precomputeExpressionRef(condExpr)) == ExpressionId.Const &&
+      _BinaryenExpressionGetType(condExpr) == NativeType.I32
+    ) {
+      let ret: ExpressionRef;
+      if (_BinaryenConstGetValueI32(condExpr)) {
+        ret = this.compileStatement(ifTrue);
+      } else if (ifFalse) {
+        ret = this.compileStatement(ifFalse);
+      } else {
+        ret = module.createNop();
+      }
+      return ret;
+    }
+
     // Each arm initiates a branch
-    var currentFunction = this.currentFunction;
     var flow = currentFunction.flow.enterBranchOrScope();
     currentFunction.flow = flow;
-    var ifTrueExpr = this.compileStatement(statement.ifTrue);
+    var ifTrueExpr = this.compileStatement(ifTrue);
     var ifTrueReturns = flow.is(FlowFlags.RETURNS);
     flow = flow.leaveBranchOrScope();
     currentFunction.flow = flow;
 
     var ifFalseExpr: ExpressionRef = 0;
     var ifFalseReturns = false;
-    var ifFalse = statement.ifFalse;
     if (ifFalse) {
       flow = flow.enterBranchOrScope();
       currentFunction.flow = flow;
@@ -1449,7 +1469,7 @@ export class Compiler extends DiagnosticEmitter {
     if (ifTrueReturns && ifFalseReturns) { // not necessary to append a hint
       flow.set(FlowFlags.RETURNS);
     }
-    return module.createIf(condition, ifTrueExpr, ifFalseExpr);
+    return module.createIf(condExpr, ifTrueExpr, ifFalseExpr);
   }
 
   compileReturnStatement(statement: ReturnStatement): ExpressionRef {
@@ -1724,12 +1744,23 @@ export class Compiler extends DiagnosticEmitter {
     var module = this.module;
 
     // The condition does not yet initialize a branch
-    var condition = makeIsTrueish(
+    var condExpr = makeIsTrueish(
       this.compileExpression(statement.condition, Type.i32, ConversionKind.NONE),
       this.currentType,
       module
     );
 
+    // Eliminate unnecesssary loops in generic contexts if the condition is constant
+    if (
+      this.currentFunction.isAny(CommonFlags.GENERIC | CommonFlags.GENERIC_CONTEXT) &&
+      _BinaryenExpressionGetId(condExpr = this.precomputeExpressionRef(condExpr)) == ExpressionId.Const &&
+      _BinaryenExpressionGetType(condExpr) == NativeType.I32
+    ) {
+      if (!_BinaryenConstGetValueI32(condExpr)) {
+        return module.createNop();
+      }
+    }
+
     // Statements initiate a new branch with its own break context
     var currentFunction = this.currentFunction;
     var label = currentFunction.enterBreakContext();
@@ -1750,7 +1781,7 @@ export class Compiler extends DiagnosticEmitter {
 
     var expr = module.createBlock(breakLabel, [
       module.createLoop(continueLabel,
-        module.createIf(condition, module.createBlock(null, [
+        module.createIf(condExpr, module.createBlock(null, [
           body,
           module.createBreak(continueLabel)
         ], NativeType.None))
@@ -4952,14 +4983,29 @@ export class Compiler extends DiagnosticEmitter {
   }
 
   compileTernaryExpression(expression: TernaryExpression, contextualType: Type): ExpressionRef {
-    var condition = makeIsTrueish(
+    var ifThen = expression.ifThen;
+    var ifElse = expression.ifElse;
+
+    var condExpr = makeIsTrueish(
       this.compileExpression(expression.condition, Type.u32, ConversionKind.NONE),
       this.currentType,
       this.module
     );
-    var ifThen = this.compileExpression(expression.ifThen, contextualType);
-    var ifElse = this.compileExpression(expression.ifElse, contextualType);
-    return this.module.createIf(condition, ifThen, ifElse);
+
+    // Eliminate unnecesssary branches in generic contexts if the condition is constant
+    if (
+      this.currentFunction.isAny(CommonFlags.GENERIC | CommonFlags.GENERIC_CONTEXT) &&
+      _BinaryenExpressionGetId(condExpr = this.precomputeExpressionRef(condExpr)) == ExpressionId.Const &&
+      _BinaryenExpressionGetType(condExpr) == NativeType.I32
+    ) {
+      return _BinaryenConstGetValueI32(condExpr)
+        ? this.compileExpression(ifThen, contextualType)
+        : this.compileExpression(ifElse, contextualType);
+    }
+
+    var ifThenExpr = this.compileExpression(ifThen, contextualType);
+    var ifElseExpr = this.compileExpression(ifElse, contextualType);
+    return this.module.createIf(condExpr, ifThenExpr, ifElseExpr);
   }
 
   compileUnaryPostfixExpression(expression: UnaryPostfixExpression, contextualType: Type): ExpressionRef {

src/diagnostics.ts

@@ -202,7 +202,6 @@ export function formatDiagnosticContext(range: Range, useColors: bool = false):
 export abstract class DiagnosticEmitter {
 
   diagnostics: DiagnosticMessage[];
-  // silentDiagnostics: bool = false;
 
   constructor(diagnostics: DiagnosticMessage[] | null = null) {
     this.diagnostics = diagnostics ? <DiagnosticMessage[]>diagnostics : new Array();

src/parser.ts

@@ -1459,12 +1459,17 @@ export class Parser extends DiagnosticEmitter {
       flags |= CommonFlags.STATIC;
       staticStart = tn.tokenPos;
       staticEnd = tn.pos;
-    } else if (tn.skip(Token.ABSTRACT)) {
-      flags |= (CommonFlags.ABSTRACT | CommonFlags.INSTANCE);
-      abstractStart = tn.tokenPos;
-      abstractEnd = tn.pos;
     } else {
-      flags |= CommonFlags.INSTANCE;
+      if (tn.skip(Token.ABSTRACT)) {
+        flags |= (CommonFlags.ABSTRACT | CommonFlags.INSTANCE);
+        abstractStart = tn.tokenPos;
+        abstractEnd = tn.pos;
+      } else {
+        flags |= CommonFlags.INSTANCE;
+      }
+      if (parentFlags & CommonFlags.GENERIC) {
+        flags |= CommonFlags.GENERIC_CONTEXT;
+      }
     }
 
     var readonlyStart: i32 = 0;
@@ -2737,12 +2742,12 @@ export class Parser extends DiagnosticEmitter {
                   // fall-through
                 }
                 // function expression
-                case Token.QUESTION:   // optional parameter
                 case Token.COLON: {    // type annotation
                   tn.reset(state);
                   return this.parseFunctionExpression(tn);
                 }
                 // can be both
+                case Token.QUESTION:   // optional parameter or ternary
                 case Token.COMMA: {
                   break; // continue
                 }

src/program.ts

@@ -2036,25 +2036,27 @@ export enum CommonFlags {
   AMBIENT = 1 << 16,
   /** Is generic. */
   GENERIC = 1 << 17,
+  /** Is part of a generic context. */
+  GENERIC_CONTEXT = 1 << 18,
   /** Is an instance member. */
-  INSTANCE = 1 << 18,
+  INSTANCE = 1 << 19,
   /** Is a constructor. */
-  CONSTRUCTOR = 1 << 19,
+  CONSTRUCTOR = 1 << 20,
   /** Is an arrow function. */
-  ARROW = 1 << 20,
+  ARROW = 1 << 21,
   /** Is a module export. */
-  MODULE_EXPORT = 1 << 21,
+  MODULE_EXPORT = 1 << 22,
   /** Is a module import. */
-  MODULE_IMPORT = 1 << 22,
+  MODULE_IMPORT = 1 << 23,
 
   // Compilation states
 
   /** Is compiled. */
-  COMPILED = 1 << 23,
+  COMPILED = 1 << 24,
   /** Has a constant value and is therefore inlined. */
-  INLINED = 1 << 24,
+  INLINED = 1 << 25,
   /** Is scoped. */
-  SCOPED = 1 << 25
+  SCOPED = 1 << 26
 }
 
 /** Base class of all program elements. */
@@ -2084,7 +2086,8 @@ export abstract class Element {
 
   /** Tests if this element has a specific flag or flags. */
   is(flag: CommonFlags): bool { return (this.flags & flag) == flag; }
-
+  /** Tests if this element has any of the specified flags. */
+  isAny(flags: CommonFlags): bool { return (this.flags & flags) != 0; }
   /** Sets a specific flag or flags. */
   set(flag: CommonFlags): void { this.flags |= flag; }
 }

std/assembly.d.ts

@@ -195,15 +195,15 @@ declare function isNaN<T = f32 | f64>(value: T): bool;
 /** Tests if a 32-bit or 64-bit float is finite, that is not `NaN` or +/-`Infinity`. */
 declare function isFinite<T = f32 | f64>(value: T): bool;
 /** Tests if the specified expression is of an integer type and not a reference. Compiles to a constant. */
-declare function isInteger(value: any): bool;
+declare function isInteger(value: any): value is number;
 /** Tests if the specified expression is of a float type. Compiles to a constant. */
-declare function isFloat(value: any): bool;
+declare function isFloat(value: any): value is number;
 /** Tests if the specified expression is of a reference type. Compiles to a constant. */
-declare function isReference(value: any): bool;
+declare function isReference(value: any): value is object | string;
 /** Tests if the specified expression can be used ass a string. Compiles to a constant. */
-declare function isString(value: any): bool;
+declare function isString(value: any): value is string | String;
 /** Tests if the specified expression can be used as an array. Compiles to a constant. */
-declare function isArray(value: any): bool;
+declare function isArray(value: any): value is Array<any>;
 /** Traps if the specified value is not true-ish, otherwise returns the (non-nullable) value. */
 declare function assert<T>(isTrueish: T, message?: string): T & object; // any better way to model `: T != null`?
 /** Parses an integer string to a 64-bit float. */

std/portable.d.ts

@@ -141,15 +141,15 @@ declare function isNaN<T = f32 | f64>(value: T): bool;
 /** Tests if a 32-bit or 64-bit float is finite, that is not `NaN` or +/-`Infinity`. */
 declare function isFinite<T = f32 | f64>(value: T): bool;
 /** Tests if the specified value is a valid integer. Can't distinguish an integer from an integral float. */
-declare function isInteger(value: any): bool;
+declare function isInteger(value: any): value is number;
 /** Tests if the specified value is a valid float. Can't distinguish a float from an integer. */
-declare function isFloat(value: any): bool;
+declare function isFloat(value: any): value is number;
 /** Tests if the specified value is of a reference type. */
-declare function isReference(value: any): bool;
+declare function isReference(value: any): value is object | string;
 /** Tests if the specified value can be used as a string. */
-declare function isString(value: any): bool;
+declare function isString(value: any): value is string | String;
 /** Tests if the specified value can be used as an array. */
-declare function isArray(value: any): bool;
+declare function isArray(value: any): value is Array<any>;
 /** Traps if the specified value is not true-ish, otherwise returns the value. */
 declare function assert<T>(isTrueish: T | null, message?: string): T;
 /** Parses an integer string to a 64-bit float. */

tests/compiler/builtins.optimized.wat

@@ -640,6 +640,12 @@
   (set_global $builtins/F
    (f64.const 25)
   )
+  (if
+   (i32.eqz
+    (get_global $builtins/i)
+   )
+   (unreachable)
+  )
   (if
    (f32.eq
     (tee_local $0

tests/compiler/builtins.ts

@@ -213,7 +213,7 @@ I = select<i64>(100, 200, false);
 f = select<f32>(1.25, 2.5, true);
 F = select<f64>(12.5, 25.0, false);
 
-if (0) unreachable();
+if (!i) unreachable();
 
 // AS specific
 

tests/compiler/builtins.untouched.wat

@@ -1221,7 +1221,9 @@
    )
   )
   (if
-   (i32.const 0)
+   (i32.eqz
+    (get_global $builtins/i)
+   )
    (unreachable)
   )
   (drop

tests/compiler/showcase.optimized.wat

@@ -4066,6 +4066,12 @@
   (set_global $builtins/F
    (f64.const 25)
   )
+  (if
+   (i32.eqz
+    (get_global $builtins/i)
+   )
+   (unreachable)
+  )
   (if
    (f32.eq
     (tee_local $1

tests/compiler/showcase.untouched.wat

@@ -5614,7 +5614,9 @@
    )
   )
   (if
-   (i32.const 0)
+   (i32.eqz
+    (get_global $builtins/i)
+   )
    (unreachable)
   )
   (drop

tests/compiler/std/carray.untouched.wat

@@ -1,6 +1,7 @@
 (module
  (type $iiiiv (func (param i32 i32 i32 i32)))
  (type $iii (func (param i32 i32) (result i32)))
+ (type $i (func (result i32)))
  (type $iiiv (func (param i32 i32 i32)))
  (type $v (func))
  (import "env" "abort" (func $abort (param i32 i32 i32 i32)))

tests/compiler/std/polyfills.optimized.wat

@@ -217,73 +217,7 @@
    (get_local $0)
   )
  )
- (func "$(lib)/polyfills/bswap16<u32>" (; 5 ;) (type $ii) (param $0 i32) (result i32)
-  (local $1 i32)
-  (if
-   (i32.eqz
-    (i32.and
-     (if (result i32)
-      (tee_local $1
-       (i32.and
-        (i32.const 0)
-        (i32.const 1)
-       )
-      )
-      (get_local $1)
-      (i32.const 1)
-     )
-     (i32.const 1)
-    )
-   )
-   (block
-    (call $abort
-     (i32.const 0)
-     (i32.const 4)
-     (i32.const 25)
-     (i32.const 2)
-    )
-    (unreachable)
-   )
-  )
-  (if
-   (i32.and
-    (if (result i32)
-     (tee_local $1
-      (i32.const 0)
-     )
-     (get_local $1)
-     (i32.const 1)
-    )
-    (i32.const 1)
-   )
-   (return
-    (i32.or
-     (i32.or
-      (i32.and
-       (i32.shl
-        (get_local $0)
-        (i32.const 8)
-       )
-       (i32.const 65280)
-      )
-      (i32.and
-       (i32.shr_u
-        (get_local $0)
-        (i32.const 8)
-       )
-       (i32.const 255)
-      )
-     )
-     (i32.and
-      (get_local $0)
-      (i32.const -65536)
-     )
-    )
-   )
-  )
-  (get_local $0)
- )
- (func "$(lib)/polyfills/bswap<u32>" (; 6 ;) (type $ii) (param $0 i32) (result i32)
+ (func "$(lib)/polyfills/bswap<u32>" (; 5 ;) (type $ii) (param $0 i32) (result i32)
   (local $1 i32)
   (if
    (i32.eqz
@@ -337,73 +271,7 @@
    )
   )
  )
- (func "$(lib)/polyfills/bswap16<i32>" (; 7 ;) (type $ii) (param $0 i32) (result i32)
-  (local $1 i32)
-  (if
-   (i32.eqz
-    (i32.and
-     (if (result i32)
-      (tee_local $1
-       (i32.and
-        (i32.const 0)
-        (i32.const 1)
-       )
-      )
-      (get_local $1)
-      (i32.const 1)
-     )
-     (i32.const 1)
-    )
-   )
-   (block
-    (call $abort
-     (i32.const 0)
-     (i32.const 4)
-     (i32.const 25)
-     (i32.const 2)
-    )
-    (unreachable)
-   )
-  )
-  (if
-   (i32.and
-    (if (result i32)
-     (tee_local $1
-      (i32.const 0)
-     )
-     (get_local $1)
-     (i32.const 1)
-    )
-    (i32.const 1)
-   )
-   (return
-    (i32.or
-     (i32.or
-      (i32.and
-       (i32.shl
-        (get_local $0)
-        (i32.const 8)
-       )
-       (i32.const 65280)
-      )
-      (i32.and
-       (i32.shr_s
-        (get_local $0)
-        (i32.const 8)
-       )
-       (i32.const 255)
-      )
-     )
-     (i32.and
-      (get_local $0)
-      (i32.const -65536)
-     )
-    )
-   )
-  )
-  (get_local $0)
- )
- (func "$(lib)/polyfills/bswap<u64>" (; 8 ;) (type $II) (param $0 i64) (result i64)
+ (func "$(lib)/polyfills/bswap<u64>" (; 6 ;) (type $II) (param $0 i64) (result i64)
   (local $1 i32)
   (if
    (i32.eqz
@@ -477,6 +345,138 @@
    (i64.const 32)
   )
  )
+ (func "$(lib)/polyfills/bswap16<u32>" (; 7 ;) (type $ii) (param $0 i32) (result i32)
+  (local $1 i32)
+  (if
+   (i32.eqz
+    (i32.and
+     (if (result i32)
+      (tee_local $1
+       (i32.and
+        (i32.const 0)
+        (i32.const 1)
+       )
+      )
+      (get_local $1)
+      (i32.const 1)
+     )
+     (i32.const 1)
+    )
+   )
+   (block
+    (call $abort
+     (i32.const 0)
+     (i32.const 4)
+     (i32.const 25)
+     (i32.const 2)
+    )
+    (unreachable)
+   )
+  )
+  (if
+   (i32.and
+    (if (result i32)
+     (tee_local $1
+      (i32.const 0)
+     )
+     (get_local $1)
+     (i32.const 1)
+    )
+    (i32.const 1)
+   )
+   (return
+    (i32.or
+     (i32.or
+      (i32.and
+       (i32.shl
+        (get_local $0)
+        (i32.const 8)
+       )
+       (i32.const 65280)
+      )
+      (i32.and
+       (i32.shr_u
+        (get_local $0)
+        (i32.const 8)
+       )
+       (i32.const 255)
+      )
+     )
+     (i32.and
+      (get_local $0)
+      (i32.const -65536)
+     )
+    )
+   )
+  )
+  (get_local $0)
+ )
+ (func "$(lib)/polyfills/bswap16<i32>" (; 8 ;) (type $ii) (param $0 i32) (result i32)
+  (local $1 i32)
+  (if
+   (i32.eqz
+    (i32.and
+     (if (result i32)
+      (tee_local $1
+       (i32.and
+        (i32.const 0)
+        (i32.const 1)
+       )
+      )
+      (get_local $1)
+      (i32.const 1)
+     )
+     (i32.const 1)
+    )
+   )
+   (block
+    (call $abort
+     (i32.const 0)
+     (i32.const 4)
+     (i32.const 25)
+     (i32.const 2)
+    )
+    (unreachable)
+   )
+  )
+  (if
+   (i32.and
+    (if (result i32)
+     (tee_local $1
+      (i32.const 0)
+     )
+     (get_local $1)
+     (i32.const 1)
+    )
+    (i32.const 1)
+   )
+   (return
+    (i32.or
+     (i32.or
+      (i32.and
+       (i32.shl
+        (get_local $0)
+        (i32.const 8)
+       )
+       (i32.const 65280)
+      )
+      (i32.and
+       (i32.shr_s
+        (get_local $0)
+        (i32.const 8)
+       )
+       (i32.const 255)
+      )
+     )
+     (i32.and
+      (get_local $0)
+      (i32.const -65536)
+     )
+    )
+   )
+  )
+  (get_local $0)
+ )
  (func $start (; 9 ;) (type $v)
   (if
    (i32.ne