[Strings] Lower string.concat in StringLowering (#6453)

3 files changed, 69 insertions, 33 deletions

diff --git a/src/passes/StringLowering.cpp b/src/passes/StringLowering.cpp
index 322f0deb2..df2d66860 100644
--- a/src/passes/StringLowering.cpp
+++ b/src/passes/StringLowering.cpp
@@ -298,6 +298,7 @@ struct StringLowering : public StringGathering {
   Name fromCharCodeArrayImport;
   Name intoCharCodeArrayImport;
   Name fromCodePointImport;
+  Name concatImport;
   Name equalsImport;
   Name compareImport;
   Name lengthImport;
@@ -328,6 +329,8 @@ struct StringLowering : public StringGathering {
       module, "fromCharCodeArray", {nullArray16, Type::i32, Type::i32}, nnExt);
     // string.fromCodePoint: codepoint -> ext
     fromCodePointImport = addImport(module, "fromCodePoint", Type::i32, nnExt);
+    // string.concat: string, string -> string
+    concatImport = addImport(module, "concat", {nullExt, nullExt}, nnExt);
     // string.intoCharCodeArray: string, array, start -> num written
     intoCharCodeArrayImport = addImport(module,
                                         "intoCharCodeArray",
@@ -375,6 +378,12 @@ struct StringLowering : public StringGathering {
         }
       }
 
+      void visitStringConcat(StringConcat* curr) {
+        Builder builder(*getModule());
+        replaceCurrent(builder.makeCall(
+          lowering.concatImport, {curr->left, curr->right}, lowering.nnExt));
+      }
+
       void visitStringAs(StringAs* curr) {
         // There is no difference between strings and views with imported
         // strings: they are all just JS strings, so no conversion is needed.
diff --git a/test/lit/passes/string-gathering.wast b/test/lit/passes/string-gathering.wast
index efa6ba130..bef342ee0 100644
--- a/test/lit/passes/string-gathering.wast
+++ b/test/lit/passes/string-gathering.wast
@@ -35,13 +35,15 @@
 
   ;; LOWER:      (type $4 (func (param i32) (result (ref extern))))
 
-  ;; LOWER:      (type $5 (func (param externref (ref null $2) i32) (result i32)))
+  ;; LOWER:      (type $5 (func (param externref externref) (result (ref extern))))
 
-  ;; LOWER:      (type $6 (func (param externref) (result i32)))
+  ;; LOWER:      (type $6 (func (param externref (ref null $2) i32) (result i32)))
 
-  ;; LOWER:      (type $7 (func (param externref i32) (result i32)))
+  ;; LOWER:      (type $7 (func (param externref) (result i32)))
 
-  ;; LOWER:      (type $8 (func (param externref i32 i32) (result (ref extern))))
+  ;; LOWER:      (type $8 (func (param externref i32) (result i32)))
+
+  ;; LOWER:      (type $9 (func (param externref i32 i32) (result (ref extern))))
 
   ;; LOWER:      (import "string.const" "0" (global $string.const_bar (ref extern)))
 
@@ -53,17 +55,19 @@
 
   ;; LOWER:      (import "wasm:js-string" "fromCodePoint" (func $fromCodePoint (type $4) (param i32) (result (ref extern))))
 
-  ;; LOWER:      (import "wasm:js-string" "intoCharCodeArray" (func $intoCharCodeArray (type $5) (param externref (ref null $2) i32) (result i32)))
+  ;; LOWER:      (import "wasm:js-string" "concat" (func $concat (type $5) (param externref externref) (result (ref extern))))
+
+  ;; LOWER:      (import "wasm:js-string" "intoCharCodeArray" (func $intoCharCodeArray (type $6) (param externref (ref null $2) i32) (result i32)))
 
   ;; LOWER:      (import "wasm:js-string" "equals" (func $equals (type $1) (param externref externref) (result i32)))
 
   ;; LOWER:      (import "wasm:js-string" "compare" (func $compare (type $1) (param externref externref) (result i32)))
 
-  ;; LOWER:      (import "wasm:js-string" "length" (func $length (type $6) (param externref) (result i32)))
+  ;; LOWER:      (import "wasm:js-string" "length" (func $length (type $7) (param externref) (result i32)))
 
-  ;; LOWER:      (import "wasm:js-string" "charCodeAt" (func $charCodeAt (type $7) (param externref i32) (result i32)))
+  ;; LOWER:      (import "wasm:js-string" "charCodeAt" (func $charCodeAt (type $8) (param externref i32) (result i32)))
 
-  ;; LOWER:      (import "wasm:js-string" "substring" (func $substring (type $8) (param externref i32 i32) (result (ref extern))))
+  ;; LOWER:      (import "wasm:js-string" "substring" (func $substring (type $9) (param externref i32 i32) (result (ref extern))))
 
   ;; LOWER:      (global $global2 externref (global.get $string.const_bar))
   (global $global2 (ref null string) (string.const "bar"))
@@ -151,13 +155,15 @@
 
   ;; LOWER:      (type $3 (func (param i32) (result (ref extern))))
 
-  ;; LOWER:      (type $4 (func (param externref (ref null $1) i32) (result i32)))
+  ;; LOWER:      (type $4 (func (param externref externref) (result (ref extern))))
 
-  ;; LOWER:      (type $5 (func (param externref) (result i32)))
+  ;; LOWER:      (type $5 (func (param externref (ref null $1) i32) (result i32)))
 
-  ;; LOWER:      (type $6 (func (param externref i32) (result i32)))
+  ;; LOWER:      (type $6 (func (param externref) (result i32)))
+
+  ;; LOWER:      (type $7 (func (param externref i32) (result i32)))
 
-  ;; LOWER:      (type $7 (func (param externref i32 i32) (result (ref extern))))
+  ;; LOWER:      (type $8 (func (param externref i32 i32) (result (ref extern))))
 
   ;; LOWER:      (import "a" "b" (global $import (ref extern)))
   (import "a" "b" (global $import (ref string)))
@@ -174,17 +180,19 @@
 
   ;; LOWER:      (import "wasm:js-string" "fromCodePoint" (func $fromCodePoint (type $3) (param i32) (result (ref extern))))
 
-  ;; LOWER:      (import "wasm:js-string" "intoCharCodeArray" (func $intoCharCodeArray (type $4) (param externref (ref null $1) i32) (result i32)))
+  ;; LOWER:      (import "wasm:js-string" "concat" (func $concat (type $4) (param externref externref) (result (ref extern))))
+
+  ;; LOWER:      (import "wasm:js-string" "intoCharCodeArray" (func $intoCharCodeArray (type $5) (param externref (ref null $1) i32) (result i32)))
 
   ;; LOWER:      (import "wasm:js-string" "equals" (func $equals (type $0) (param externref externref) (result i32)))
 
   ;; LOWER:      (import "wasm:js-string" "compare" (func $compare (type $0) (param externref externref) (result i32)))
 
-  ;; LOWER:      (import "wasm:js-string" "length" (func $length (type $5) (param externref) (result i32)))
+  ;; LOWER:      (import "wasm:js-string" "length" (func $length (type $6) (param externref) (result i32)))
 
-  ;; LOWER:      (import "wasm:js-string" "charCodeAt" (func $charCodeAt (type $6) (param externref i32) (result i32)))
+  ;; LOWER:      (import "wasm:js-string" "charCodeAt" (func $charCodeAt (type $7) (param externref i32) (result i32)))
 
-  ;; LOWER:      (import "wasm:js-string" "substring" (func $substring (type $7) (param externref i32 i32) (result (ref extern))))
+  ;; LOWER:      (import "wasm:js-string" "substring" (func $substring (type $8) (param externref i32 i32) (result (ref extern))))
 
   ;; LOWER:      (global $global2 (ref extern) (global.get $global1))
   (global $global2 (ref string) (string.const "foo"))
diff --git a/test/lit/passes/string-lowering-instructions.wast b/test/lit/passes/string-lowering-instructions.wast
index 97186fba7..548586c4b 100644
--- a/test/lit/passes/string-lowering-instructions.wast
+++ b/test/lit/passes/string-lowering-instructions.wast
@@ -50,21 +50,25 @@
 
   ;; CHECK:       (type $17 (func (param externref (ref $0)) (result i32)))
 
-  ;; CHECK:       (type $18 (func (param (ref $0))))
+  ;; CHECK:       (type $18 (func (param externref externref) (result (ref extern))))
 
-  ;; CHECK:       (type $19 (func (param externref (ref extern) externref externref externref (ref extern))))
+  ;; CHECK:       (type $19 (func (param (ref $0))))
 
-  ;; CHECK:      (type $20 (func (param (ref null $0) i32 i32) (result (ref extern))))
+  ;; CHECK:       (type $20 (func (param externref (ref extern) externref externref externref (ref extern))))
 
-  ;; CHECK:      (type $21 (func (param i32) (result (ref extern))))
+  ;; CHECK:      (type $21 (func (param (ref null $0) i32 i32) (result (ref extern))))
 
-  ;; CHECK:      (type $22 (func (param externref (ref null $0) i32) (result i32)))
+  ;; CHECK:      (type $22 (func (param i32) (result (ref extern))))
 
-  ;; CHECK:      (type $23 (func (param externref) (result i32)))
+  ;; CHECK:      (type $23 (func (param externref externref) (result (ref extern))))
 
-  ;; CHECK:      (type $24 (func (param externref i32) (result i32)))
+  ;; CHECK:      (type $24 (func (param externref (ref null $0) i32) (result i32)))
 
-  ;; CHECK:      (type $25 (func (param externref i32 i32) (result (ref extern))))
+  ;; CHECK:      (type $25 (func (param externref) (result i32)))
+
+  ;; CHECK:      (type $26 (func (param externref i32) (result i32)))
+
+  ;; CHECK:      (type $27 (func (param externref i32 i32) (result (ref extern))))
 
   ;; CHECK:      (import "string.const" "0" (global $string.const_exported (ref extern)))
 
@@ -74,21 +78,23 @@
   (import "colliding" "name" (func $fromCodePoint))
 
 
-  ;; CHECK:      (import "wasm:js-string" "fromCharCodeArray" (func $fromCharCodeArray (type $20) (param (ref null $0) i32 i32) (result (ref extern))))
+  ;; CHECK:      (import "wasm:js-string" "fromCharCodeArray" (func $fromCharCodeArray (type $21) (param (ref null $0) i32 i32) (result (ref extern))))
 
-  ;; CHECK:      (import "wasm:js-string" "fromCodePoint" (func $fromCodePoint_18 (type $21) (param i32) (result (ref extern))))
+  ;; CHECK:      (import "wasm:js-string" "fromCodePoint" (func $fromCodePoint_19 (type $22) (param i32) (result (ref extern))))
 
-  ;; CHECK:      (import "wasm:js-string" "intoCharCodeArray" (func $intoCharCodeArray (type $22) (param externref (ref null $0) i32) (result i32)))
+  ;; CHECK:      (import "wasm:js-string" "concat" (func $concat (type $23) (param externref externref) (result (ref extern))))
+
+  ;; CHECK:      (import "wasm:js-string" "intoCharCodeArray" (func $intoCharCodeArray (type $24) (param externref (ref null $0) i32) (result i32)))
 
   ;; CHECK:      (import "wasm:js-string" "equals" (func $equals (type $2) (param externref externref) (result i32)))
 
   ;; CHECK:      (import "wasm:js-string" "compare" (func $compare (type $2) (param externref externref) (result i32)))
 
-  ;; CHECK:      (import "wasm:js-string" "length" (func $length (type $23) (param externref) (result i32)))
+  ;; CHECK:      (import "wasm:js-string" "length" (func $length (type $25) (param externref) (result i32)))
 
-  ;; CHECK:      (import "wasm:js-string" "charCodeAt" (func $charCodeAt (type $24) (param externref i32) (result i32)))
+  ;; CHECK:      (import "wasm:js-string" "charCodeAt" (func $charCodeAt (type $26) (param externref i32) (result i32)))
 
-  ;; CHECK:      (import "wasm:js-string" "substring" (func $substring (type $25) (param externref i32 i32) (result (ref extern))))
+  ;; CHECK:      (import "wasm:js-string" "substring" (func $substring (type $27) (param externref i32 i32) (result (ref extern))))
 
   ;; CHECK:      (global $string externref (ref.null noextern))
   (global $string stringref (ref.null string)) ;; Test we update global nulls.
@@ -97,7 +103,7 @@
 
   ;; CHECK:      (export "export.2" (func $exported-string-receiver))
 
-  ;; CHECK:      (func $string.as (type $19) (param $a externref) (param $a_nn (ref extern)) (param $b externref) (param $c externref) (param $d externref) (param $nn_view (ref extern))
+  ;; CHECK:      (func $string.as (type $20) (param $a externref) (param $a_nn (ref extern)) (param $b externref) (param $c externref) (param $d externref) (param $nn_view (ref extern))
   ;; CHECK-NEXT:  (local.set $b
   ;; CHECK-NEXT:   (ref.as_non_null
   ;; CHECK-NEXT:    (local.get $a)
@@ -163,7 +169,7 @@
     )
   )
 
-  ;; CHECK:      (func $string.new.gc (type $18) (param $array16 (ref $0))
+  ;; CHECK:      (func $string.new.gc (type $19) (param $array16 (ref $0))
   ;; CHECK-NEXT:  (drop
   ;; CHECK-NEXT:   (call $fromCharCodeArray
   ;; CHECK-NEXT:    (local.get $array16)
@@ -183,7 +189,7 @@
   )
 
   ;; CHECK:      (func $string.from_code_point (type $4) (result externref)
-  ;; CHECK-NEXT:  (call $fromCodePoint_18
+  ;; CHECK-NEXT:  (call $fromCodePoint_19
   ;; CHECK-NEXT:   (i32.const 1)
   ;; CHECK-NEXT:  )
   ;; CHECK-NEXT: )
@@ -193,6 +199,19 @@
     )
   )
 
+  ;; CHECK:      (func $string.concat (type $18) (param $0 externref) (param $1 externref) (result (ref extern))
+  ;; CHECK-NEXT:  (call $concat
+  ;; CHECK-NEXT:   (local.get $0)
+  ;; CHECK-NEXT:   (local.get $1)
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT: )
+  (func $string.concat (param stringref stringref) (result (ref string))
+   (string.concat
+    (local.get 0)
+    (local.get 1)
+   )
+  )
+
   ;; CHECK:      (func $string.encode (type $17) (param $ref externref) (param $array16 (ref $0)) (result i32)
   ;; CHECK-NEXT:  (call $intoCharCodeArray
   ;; CHECK-NEXT:   (local.get $ref)