[wasm-split] Split more active segments for --no-placeholders

src/ir/module-splitting.cpp

@@ -871,6 +871,8 @@ ModuleSplitter::PrimarySecondaryUsedNames ModuleSplitter::computeUsedNames() {
   // primary module and scan it there.
   ModuleUtils::iterActiveDataSegments(primary, [&](DataSegment* segment) {
     UsedNames* owner = getOwner(segment->memory, &UsedNames::memories);
+    // Trapping segments should be kept in the primary module because they are
+    // evaluated at the instantiation time.
     if (mayTrap(segment)) {
       owner = &primaryUsed;
     }
@@ -886,6 +888,39 @@ ModuleSplitter::PrimarySecondaryUsedNames ModuleSplitter::computeUsedNames() {
 
   ModuleUtils::iterActiveElementSegments(primary, [&](ElementSegment* segment) {
     UsedNames* owner = getOwner(segment->table, &UsedNames::tables);
+
+    // If placeholders are NOT used, and if all functions in an element segment
+    // belong to a single secondary module, we can move the segment to that
+    // secondary module, because those functions aren't available until the
+    // secondary module is loaded anyway.
+    if (!config.usePlaceholders && segment->type.isFunction() &&
+        owner == &primaryUsed) {
+      bool foundSecondary = false;
+      Index secondaryIndex = 0;
+      bool keepInPrimary = false;
+      for (auto* item : segment->data) {
+        if (item->is<GlobalGet>()) {
+          keepInPrimary = true;
+          break;
+        } else if (auto* ref = item->dynCast<RefFunc>()) {
+          auto it = funcToSecondaryIndex.find(ref->func);
+          if (it == funcToSecondaryIndex.end()) {
+            keepInPrimary = true;
+            break;
+          }
+          if (foundSecondary && secondaryIndex != it->second) {
+            keepInPrimary = true;
+            break;
+          }
+          foundSecondary = true;
+          secondaryIndex = it->second;
+        }
+      }
+      if (!keepInPrimary && foundSecondary) {
+        owner = &secondaryUsed[secondaryIndex];
+      }
+    }
+
     if (mayTrap(segment)) {
       owner = &primaryUsed;
     }

test/lit/wasm-split/multi-split-elems-no-placeholders.wast

@@ -0,0 +1,50 @@
+;; NOTE: Assertions have been generated by update_lit_checks.py and should not be edited.
+;; RUN: wasm-split -all -g --multi-split %s --no-placeholders --manifest %S/multi-split.wast.manifest --out-prefix=%t -o %t.wasm
+;; RUN: wasm-dis %t.wasm | filecheck %s --check-prefix=PRIMARY
+;; RUN: wasm-dis %t1.wasm | filecheck %s --check-prefix=MOD1
+;; RUN: wasm-dis %t2.wasm | filecheck %s --check-prefix=MOD2
+;; RUN: wasm-dis %t3.wasm | filecheck %s --check-prefix=MOD3
+
+;; When placeholders are NOT used and all functions in an element segment belong
+;; to a single secondary module, we can move the segment to that secondary
+;; module.
+
+(module
+ ;; PRIMARY:      (table $table 3 3 funcref)
+ (table $table 3 3 funcref)
+ ;; PRIMARY:      (elem $primary-elem1 (table $table) (i32.const 0) func $trampoline_A $trampoline_B $trampoline_C)
+
+ ;; PRIMARY:      (elem $primary-elem2 (table $table) (i32.const 0) func $trampoline_A $trampoline_B $trampoline_A)
+
+ ;; PRIMARY:      (export "table" (table $table))
+ (export "table" (table $table))
+ (elem $primary-elem1 (table $table) (i32.const 0) func $A $B $C)
+ (elem $primary-elem2 (table $table) (i32.const 0) func $A $B $A)
+ ;; MOD1:      (elem $A-elem (table $table) (i32.const 0) func $A $A $A)
+ (elem $A-elem (table $table) (i32.const 0) func $A $A $A)
+ ;; MOD2:      (elem $B-elem (table $table) (i32.const 0) func $B $B $B)
+ (elem $B-elem (table $table) (i32.const 0) func $B $B $B)
+ ;; MOD3:      (elem $C-elem (table $table) (i32.const 0) func $C $C $C)
+ (elem $C-elem (table $table) (i32.const 0) func $C $C $C)
+
+ ;; MOD1:      (func $A
+ ;; MOD1-NEXT:  (call_indirect (type $0)
+ ;; MOD1-NEXT:   (i32.const 0)
+ ;; MOD1-NEXT:  )
+ ;; MOD1-NEXT: )
+ (func $A
+  (call_indirect $table
+   (i32.const 0)
+  )
+ )
+
+ ;; MOD2:      (func $B
+ ;; MOD2-NEXT: )
+ (func $B
+ )
+
+ ;; MOD3:      (func $C
+ ;; MOD3-NEXT: )
+ (func $C
+ )
+)

test/lit/wasm-split/split-elems-no-placeholders.wast

@@ -0,0 +1,97 @@
+;; NOTE: Assertions have been generated by update_lit_checks.py and should not be edited.
+;; RUN: wasm-split %s -all --no-placeholders -g -o1 %t.1.wasm -o2 %t.2.wasm --keep-funcs=keep
+;; RUN: wasm-dis %t.1.wasm -all | filecheck %s --check-prefix PRIMARY
+;; RUN: wasm-dis %t.2.wasm -all | filecheck %s --check-prefix SECONDARY
+
+;; When placeholders are NOT used and all functions in an element segment belong
+;; to a single secondary module, we can move the segment to that secondary
+;; module.
+
+(module
+ ;; PRIMARY:      (global $keep-global funcref (ref.func $trampoline_split))
+ (global $keep-global funcref (ref.func $split))
+ ;; PRIMARY:      (table $keep-table 2 2 funcref)
+ (table $keep-table 2 2 funcref)
+ ;; PRIMARY:      (table $keep-table2 1 1 externref)
+ (table $keep-table2 1 1 externref)
+ ;; This contains both a primary function and a secondary function, so keep this
+ ;; in the primary.
+ ;; PRIMARY:      (elem $keep-elem1 (table $keep-table) (i32.const 0) func $keep $trampoline_split)
+ (elem $keep-elem1 (table $keep-table) (i32.const 0) func $keep $split)
+ ;; This contains a global.get, so keep it in the primary.
+ ;; PRIMARY:      (elem $keep-elem2 (table $keep-table) (i32.const 0) funcref (item (ref.func $trampoline_split)) (item (global.get $keep-global)))
+ (elem $keep-elem2 (table $keep-table) (i32.const 0) funcref (ref.func $split) (global.get $keep-global))
+ ;; This is not a funcref table, and the referenced table is kept in the
+ ;; primary. So keep this in the primary too.
+ ;; PRIMARY:      (elem $keep-elem3 (table $keep-table2) (i32.const 0) externref (item (ref.null noextern)))
+ (elem $keep-elem3 (table $keep-table2) (i32.const 0) externref (ref.null extern))
+ ;; The offset exceeds the table size, so keep this in the primary.
+ ;; PRIMARY:      (elem $keep-elem4 (table $keep-table) (i32.const 10) func $trampoline_split)
+ (elem $keep-elem4 (table $keep-table) (i32.const 10) func $split)
+
+ ;; SECONDARY:      (global $split-global funcref (ref.func $split))
+ (global $split-global funcref (ref.func $split))
+ ;; SECONDARY:      (table $split-table 2 2 funcref)
+ (table $split-table 2 2 funcref)
+
+ ;; All functions are in the secondary module, so split this to the secondary,
+ ;; even if the referenced table is in the primary module.
+ ;; SECONDARY:      (elem $split-elem1 (table $keep-table) (i32.const 0) func $split $split)
+ (elem $split-elem1 (table $keep-table) (i32.const 0) func $split $split)
+ ;; The same test with $split-table.
+ ;; SECONDARY:      (elem $split-elem2 (table $split-table) (i32.const 0) func $split $split)
+ (elem $split-elem2 (table $split-table) (i32.const 0) func $split $split)
+ ;; ref.null within data doesn't affect the segment's splitability.
+ ;; SECONDARY:      (elem $split-elem3 (table $split-table) (i32.const 0) funcref (item (ref.func $split)) (item (ref.null nofunc)))
+ (elem $split-elem3 (table $split-table) (i32.const 0) funcref (ref.func $split) (ref.null nofunc))
+
+ ;; PRIMARY:      (func $keep (type $0)
+ ;; PRIMARY-NEXT:  (call_indirect $keep-table (type $0)
+ ;; PRIMARY-NEXT:   (i32.const 0)
+ ;; PRIMARY-NEXT:  )
+ ;; PRIMARY-NEXT:  (drop
+ ;; PRIMARY-NEXT:   (table.get $keep-table2
+ ;; PRIMARY-NEXT:    (i32.const 0)
+ ;; PRIMARY-NEXT:   )
+ ;; PRIMARY-NEXT:  )
+ ;; PRIMARY-NEXT:  (drop
+ ;; PRIMARY-NEXT:   (global.get $keep-global)
+ ;; PRIMARY-NEXT:  )
+ ;; PRIMARY-NEXT: )
+ (func $keep
+  ;; Uses $keep-table
+  (call_indirect $keep-table
+    (i32.const 0)
+  )
+  ;; Uses $keep-table2
+  (drop
+    (table.get $keep-table2
+      (i32.const 0)
+    )
+  )
+  ;; Uses $keep-global
+  (drop
+   (global.get $keep-global)
+  )
+ )
+
+ ;; SECONDARY:      (func $split (type $0)
+ ;; SECONDARY-NEXT:  (call_indirect $split-table (type $0)
+ ;; SECONDARY-NEXT:   (i32.const 0)
+ ;; SECONDARY-NEXT:  )
+ ;; SECONDARY-NEXT:  (drop
+ ;; SECONDARY-NEXT:   (global.get $split-global)
+ ;; SECONDARY-NEXT:  )
+ ;; SECONDARY-NEXT: )
+ (func $split
+  ;; Uses $split-table
+  (call_indirect $split-table
+   (i32.const 0)
+  )
+  ;; Uses $split-global
+  (drop
+   (global.get $split-global)
+  )
+ )
+)
+