Use hints when generating fresh labels in IRBuilder

IRBuilder often has to generate new label names for blocks and other scopes. Previously it would generate each new name by starting with "block" or "label" and incrementing a suffix until finding a fresh name, but this made name generation quadratic in the number of names to generate. To spend less time generating names, track a hint index at which to start looking for a fresh name and increment it every time a name is generated. This speeds up a version of the binary parser that uses IRBuilder by about 15%.
WebAssembly · Nov 18, 2024 · 5b2c76f · 5b2c76f
1 parent 3981163
commit 5b2c76f
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Showing 8 changed files with 87 additions and 82 deletions.
diff --git a/src/wasm-ir-builder.h b/src/wasm-ir-builder.h
@@ -507,16 +507,19 @@ class IRBuilder : public UnifiedExpressionVisitor<IRBuilder, Result<>> {
   // its stack.
   std::unordered_map<Name, std::vector<Index>> labelDepths;
 
-  Name makeFresh(Name label) {
+  Name makeFresh(Name label, Index hint = 0) {
     return Names::getValidName(
       label,
       [&](Name candidate) {
         return labelDepths.insert({candidate, {}}).second;
       },
-      0,
+      hint,
       "");
   }
 
+  Index blockHint = 0;
+  Index labelHint = 0;
+
   void pushScope(ScopeCtx scope) {
     if (auto label = scope.getOriginalLabel()) {
       // Assign a fresh label to the scope, if necessary.

diff --git a/src/wasm/wasm-ir-builder.cpp b/src/wasm/wasm-ir-builder.cpp
@@ -987,6 +987,8 @@ Result<> IRBuilder::visitEnd() {
       EHUtils::handleBlockNestedPops(func, wasm);
     }
     this->func = nullptr;
+    blockHint = 0;
+    labelHint = 0;
   } else if (auto* block = scope.getBlock()) {
     assert(*expr == block);
     block->name = scope.label;
@@ -1073,9 +1075,9 @@ Result<Name> IRBuilder::getLabelName(Index label, bool forDelegate) {
   if (!scopeLabel) {
     // The scope does not already have a name, so we need to create one.
     if ((*scope)->getBlock()) {
-      scopeLabel = makeFresh("block");
+      scopeLabel = makeFresh("block", blockHint++);
     } else {
-      scopeLabel = makeFresh("label");
+      scopeLabel = makeFresh("label", labelHint++);
     }
   }
   if (!forDelegate) {

diff --git a/test/lit/basic/reference-types.wast b/test/lit/basic/reference-types.wast
@@ -361,88 +361,88 @@
   ;; CHECK-TEXT-NEXT:   )
   ;; CHECK-TEXT-NEXT:  )
   ;; CHECK-TEXT-NEXT:  (drop
-  ;; CHECK-TEXT-NEXT:   (block $block0 (result eqref)
-  ;; CHECK-TEXT-NEXT:    (br_if $block0
-  ;; CHECK-TEXT-NEXT:     (global.get $global_eqref)
-  ;; CHECK-TEXT-NEXT:     (i32.const 1)
-  ;; CHECK-TEXT-NEXT:    )
-  ;; CHECK-TEXT-NEXT:   )
-  ;; CHECK-TEXT-NEXT:  )
-  ;; CHECK-TEXT-NEXT:  (drop
   ;; CHECK-TEXT-NEXT:   (block $block1 (result eqref)
   ;; CHECK-TEXT-NEXT:    (br_if $block1
-  ;; CHECK-TEXT-NEXT:     (ref.null none)
+  ;; CHECK-TEXT-NEXT:     (global.get $global_eqref)
   ;; CHECK-TEXT-NEXT:     (i32.const 1)
   ;; CHECK-TEXT-NEXT:    )
   ;; CHECK-TEXT-NEXT:   )
   ;; CHECK-TEXT-NEXT:  )
   ;; CHECK-TEXT-NEXT:  (drop
-  ;; CHECK-TEXT-NEXT:   (block $block2 (result funcref)
+  ;; CHECK-TEXT-NEXT:   (block $block2 (result eqref)
   ;; CHECK-TEXT-NEXT:    (br_if $block2
-  ;; CHECK-TEXT-NEXT:     (local.get $local_funcref)
+  ;; CHECK-TEXT-NEXT:     (ref.null none)
   ;; CHECK-TEXT-NEXT:     (i32.const 1)
   ;; CHECK-TEXT-NEXT:    )
   ;; CHECK-TEXT-NEXT:   )
   ;; CHECK-TEXT-NEXT:  )
   ;; CHECK-TEXT-NEXT:  (drop
   ;; CHECK-TEXT-NEXT:   (block $block3 (result funcref)
   ;; CHECK-TEXT-NEXT:    (br_if $block3
-  ;; CHECK-TEXT-NEXT:     (global.get $global_funcref)
+  ;; CHECK-TEXT-NEXT:     (local.get $local_funcref)
   ;; CHECK-TEXT-NEXT:     (i32.const 1)
   ;; CHECK-TEXT-NEXT:    )
   ;; CHECK-TEXT-NEXT:   )
   ;; CHECK-TEXT-NEXT:  )
   ;; CHECK-TEXT-NEXT:  (drop
   ;; CHECK-TEXT-NEXT:   (block $block4 (result funcref)
   ;; CHECK-TEXT-NEXT:    (br_if $block4
-  ;; CHECK-TEXT-NEXT:     (ref.null nofunc)
+  ;; CHECK-TEXT-NEXT:     (global.get $global_funcref)
   ;; CHECK-TEXT-NEXT:     (i32.const 1)
   ;; CHECK-TEXT-NEXT:    )
   ;; CHECK-TEXT-NEXT:   )
   ;; CHECK-TEXT-NEXT:  )
   ;; CHECK-TEXT-NEXT:  (drop
   ;; CHECK-TEXT-NEXT:   (block $block5 (result funcref)
   ;; CHECK-TEXT-NEXT:    (br_if $block5
-  ;; CHECK-TEXT-NEXT:     (ref.func $foo)
+  ;; CHECK-TEXT-NEXT:     (ref.null nofunc)
   ;; CHECK-TEXT-NEXT:     (i32.const 1)
   ;; CHECK-TEXT-NEXT:    )
   ;; CHECK-TEXT-NEXT:   )
   ;; CHECK-TEXT-NEXT:  )
   ;; CHECK-TEXT-NEXT:  (drop
-  ;; CHECK-TEXT-NEXT:   (block $block6 (result anyref)
+  ;; CHECK-TEXT-NEXT:   (block $block6 (result funcref)
   ;; CHECK-TEXT-NEXT:    (br_if $block6
-  ;; CHECK-TEXT-NEXT:     (local.get $local_anyref)
+  ;; CHECK-TEXT-NEXT:     (ref.func $foo)
   ;; CHECK-TEXT-NEXT:     (i32.const 1)
   ;; CHECK-TEXT-NEXT:    )
   ;; CHECK-TEXT-NEXT:   )
   ;; CHECK-TEXT-NEXT:  )
   ;; CHECK-TEXT-NEXT:  (drop
   ;; CHECK-TEXT-NEXT:   (block $block7 (result anyref)
   ;; CHECK-TEXT-NEXT:    (br_if $block7
-  ;; CHECK-TEXT-NEXT:     (global.get $global_anyref)
+  ;; CHECK-TEXT-NEXT:     (local.get $local_anyref)
   ;; CHECK-TEXT-NEXT:     (i32.const 1)
   ;; CHECK-TEXT-NEXT:    )
   ;; CHECK-TEXT-NEXT:   )
   ;; CHECK-TEXT-NEXT:  )
   ;; CHECK-TEXT-NEXT:  (drop
   ;; CHECK-TEXT-NEXT:   (block $block8 (result anyref)
   ;; CHECK-TEXT-NEXT:    (br_if $block8
-  ;; CHECK-TEXT-NEXT:     (ref.null none)
+  ;; CHECK-TEXT-NEXT:     (global.get $global_anyref)
   ;; CHECK-TEXT-NEXT:     (i32.const 1)
   ;; CHECK-TEXT-NEXT:    )
   ;; CHECK-TEXT-NEXT:   )
   ;; CHECK-TEXT-NEXT:  )
   ;; CHECK-TEXT-NEXT:  (drop
   ;; CHECK-TEXT-NEXT:   (block $block9 (result anyref)
   ;; CHECK-TEXT-NEXT:    (br_if $block9
-  ;; CHECK-TEXT-NEXT:     (local.get $local_eqref)
+  ;; CHECK-TEXT-NEXT:     (ref.null none)
   ;; CHECK-TEXT-NEXT:     (i32.const 1)
   ;; CHECK-TEXT-NEXT:    )
   ;; CHECK-TEXT-NEXT:   )
   ;; CHECK-TEXT-NEXT:  )
   ;; CHECK-TEXT-NEXT:  (drop
   ;; CHECK-TEXT-NEXT:   (block $block10 (result anyref)
   ;; CHECK-TEXT-NEXT:    (br_if $block10
+  ;; CHECK-TEXT-NEXT:     (local.get $local_eqref)
+  ;; CHECK-TEXT-NEXT:     (i32.const 1)
+  ;; CHECK-TEXT-NEXT:    )
+  ;; CHECK-TEXT-NEXT:   )
+  ;; CHECK-TEXT-NEXT:  )
+  ;; CHECK-TEXT-NEXT:  (drop
+  ;; CHECK-TEXT-NEXT:   (block $block11 (result anyref)
+  ;; CHECK-TEXT-NEXT:    (br_if $block11
   ;; CHECK-TEXT-NEXT:     (ref.null none)
   ;; CHECK-TEXT-NEXT:     (i32.const 1)
   ;; CHECK-TEXT-NEXT:    )

diff --git a/test/lit/passes/outlining.wast b/test/lit/passes/outlining.wast
@@ -675,8 +675,8 @@
   ;; CHECK:      (func $a (type $1) (param $0 i32) (result i32)
   ;; CHECK-NEXT:  (call $outline$)
   ;; CHECK-NEXT:  (block $block
-  ;; CHECK-NEXT:   (block $block0
-  ;; CHECK-NEXT:    (br_table $block $block0
+  ;; CHECK-NEXT:   (block $block1
+  ;; CHECK-NEXT:    (br_table $block $block1
   ;; CHECK-NEXT:     (local.get $0)
   ;; CHECK-NEXT:    )
   ;; CHECK-NEXT:    (return

diff --git a/test/lit/wat-kitchen-sink.wast b/test/lit/wat-kitchen-sink.wast
@@ -2570,14 +2570,14 @@
  )
 
  ;; CHECK:      (func $label-index (type $0)
- ;; CHECK-NEXT:  (block $block1
+ ;; CHECK-NEXT:  (block $block2
  ;; CHECK-NEXT:   (block $block
- ;; CHECK-NEXT:    (block $block0
+ ;; CHECK-NEXT:    (block $block1
  ;; CHECK-NEXT:     (block $l
  ;; CHECK-NEXT:      (br $block)
- ;; CHECK-NEXT:      (br $block0)
- ;; CHECK-NEXT:      (br $l)
  ;; CHECK-NEXT:      (br $block1)
+ ;; CHECK-NEXT:      (br $l)
+ ;; CHECK-NEXT:      (br $block2)
  ;; CHECK-NEXT:     )
  ;; CHECK-NEXT:    )
  ;; CHECK-NEXT:   )
@@ -2844,9 +2844,9 @@
  ;; CHECK:      (func $br-table-index (type $0)
  ;; CHECK-NEXT:  (block $block
  ;; CHECK-NEXT:   (block $l
- ;; CHECK-NEXT:    (block $block1
- ;; CHECK-NEXT:     (block $block0
- ;; CHECK-NEXT:      (br_table $block $l $block0 $block1
+ ;; CHECK-NEXT:    (block $block2
+ ;; CHECK-NEXT:     (block $block1
+ ;; CHECK-NEXT:      (br_table $block $l $block1 $block2
  ;; CHECK-NEXT:       (i32.const 0)
  ;; CHECK-NEXT:      )
  ;; CHECK-NEXT:     )
@@ -4821,9 +4821,9 @@
  ;; CHECK-NEXT:   (drop
  ;; CHECK-NEXT:    (block $block (result (ref $to-f32-cont))
  ;; CHECK-NEXT:     (tuple.drop 3
- ;; CHECK-NEXT:      (block $block0 (type $34) (result i32 i64 (ref null $simple-cont))
+ ;; CHECK-NEXT:      (block $block1 (type $34) (result i32 i64 (ref null $simple-cont))
  ;; CHECK-NEXT:       (local.set $f
- ;; CHECK-NEXT:        (resume $simple-cont (on $empty $block) (on $tag-pair-to-pair $block0)
+ ;; CHECK-NEXT:        (resume $simple-cont (on $empty $block) (on $tag-pair-to-pair $block1)
  ;; CHECK-NEXT:         (i32.const 0)
  ;; CHECK-NEXT:         (i64.const 1)
  ;; CHECK-NEXT:         (local.get $ct)