OptimizeInstructions: Simplify tuple.extract of tuple.make (#5938)

E.g. (tuple.extract 1 (tuple.make (A) (B) (C)) => (B) Modify some existing tests to not be in this trivial form, so that they do not stop testing what they should.
WebAssembly · Sep 14, 2023 · 183d4b0 · 183d4b0
1 parent 2cbe448
commit 183d4b0
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Showing 2 changed files with 90 additions and 32 deletions.
diff --git a/src/passes/OptimizeInstructions.cpp b/src/passes/OptimizeInstructions.cpp
@@ -2266,6 +2266,25 @@ struct OptimizeInstructions
     }
   }
 
+  void visitTupleExtract(TupleExtract* curr) {
+    if (curr->type == Type::unreachable) {
+      return;
+    }
+
+    if (auto* make = curr->tuple->dynCast<TupleMake>()) {
+      Builder builder(*getModule());
+
+      // Store the value of the lane we want in a tee, and return that after a
+      // drop of the tuple (which might have side effects).
+      auto valueType = make->type[curr->index];
+      Index tempLocal = builder.addVar(getFunction(), valueType);
+      make->operands[curr->index] =
+        builder.makeLocalTee(tempLocal, make->operands[curr->index], valueType);
+      auto* get = builder.makeLocalGet(tempLocal, valueType);
+      replaceCurrent(getDroppedChildrenAndAppend(make, get));
+    }
+  }
+
   Index getMaxBitsForLocal(LocalGet* get) {
     // check what we know about the local
     return localInfo[get->index].maxBits;

diff --git a/test/lit/passes/optimize-instructions-multivalue.wast b/test/lit/passes/optimize-instructions-multivalue.wast
@@ -3,72 +3,111 @@
 
 (module
   ;; CHECK:      (func $if-identical-arms-tuple (param $x i32) (result i32)
+  ;; CHECK-NEXT:  (local $tuple (i32 i32))
+  ;; CHECK-NEXT:  (local $tuple2 (i32 i32))
   ;; CHECK-NEXT:  (tuple.extract 0
   ;; CHECK-NEXT:   (if (result i32 i32)
   ;; CHECK-NEXT:    (local.get $x)
-  ;; CHECK-NEXT:    (tuple.make
-  ;; CHECK-NEXT:     (i32.const 0)
-  ;; CHECK-NEXT:     (i32.const 1)
-  ;; CHECK-NEXT:    )
-  ;; CHECK-NEXT:    (tuple.make
-  ;; CHECK-NEXT:     (i32.const 2)
-  ;; CHECK-NEXT:     (i32.const 3)
-  ;; CHECK-NEXT:    )
+  ;; CHECK-NEXT:    (local.get $tuple)
+  ;; CHECK-NEXT:    (local.get $tuple2)
   ;; CHECK-NEXT:   )
   ;; CHECK-NEXT:  )
   ;; CHECK-NEXT: )
   (func $if-identical-arms-tuple (param $x i32) (result i32)
+    (local $tuple (i32 i32))
+    (local $tuple2 (i32 i32))
     (if (result i32)
       (local.get $x)
       ;; The tuple.extract can be hoisted out.
       (tuple.extract 0
-        (tuple.make
-          (i32.const 0)
-          (i32.const 1)
-        )
+        (local.get $tuple)
       )
       (tuple.extract 0
-        (tuple.make
-          (i32.const 2)
-          (i32.const 3)
-        )
+        (local.get $tuple2)
       )
     )
   )
   ;; CHECK:      (func $select-identical-arms-tuple (param $x i32) (result i32)
+  ;; CHECK-NEXT:  (local $tuple (i32 i32))
+  ;; CHECK-NEXT:  (local $tuple2 (i32 i32))
   ;; CHECK-NEXT:  (select
   ;; CHECK-NEXT:   (tuple.extract 0
-  ;; CHECK-NEXT:    (tuple.make
-  ;; CHECK-NEXT:     (i32.const 0)
-  ;; CHECK-NEXT:     (i32.const 1)
-  ;; CHECK-NEXT:    )
+  ;; CHECK-NEXT:    (local.get $tuple)
   ;; CHECK-NEXT:   )
   ;; CHECK-NEXT:   (tuple.extract 0
-  ;; CHECK-NEXT:    (tuple.make
-  ;; CHECK-NEXT:     (i32.const 2)
-  ;; CHECK-NEXT:     (i32.const 3)
-  ;; CHECK-NEXT:    )
+  ;; CHECK-NEXT:    (local.get $tuple2)
   ;; CHECK-NEXT:   )
   ;; CHECK-NEXT:   (local.get $x)
   ;; CHECK-NEXT:  )
   ;; CHECK-NEXT: )
   (func $select-identical-arms-tuple (param $x i32) (result i32)
+    (local $tuple (i32 i32))
+    (local $tuple2 (i32 i32))
     (select
       ;; The tuple.extract cannot be hoisted out, as the spec disallows a
       ;; select with multiple values in its arms.
       (tuple.extract 0
-        (tuple.make
-          (i32.const 0)
-          (i32.const 1)
-        )
+        (local.get $tuple)
       )
       (tuple.extract 0
-        (tuple.make
-          (i32.const 2)
-          (i32.const 3)
-        )
+        (local.get $tuple2)
       )
       (local.get $x)
     )
   )
+
+  ;; CHECK:      (func $extract-make (param $x i32) (param $y i32) (result i32)
+  ;; CHECK-NEXT:  (local $2 i32)
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (local.tee $2
+  ;; CHECK-NEXT:    (local.get $x)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (local.get $2)
+  ;; CHECK-NEXT: )
+  (func $extract-make (param $x i32) (param $y i32) (result i32)
+    ;; An extraction from a make can be simplified to just get the right lane.
+    (tuple.extract 0
+      (tuple.make
+        (local.get $x)
+        (local.get $y)
+      )
+    )
+  )
+
+  ;; CHECK:      (func $extract-make-2 (param $x i32) (param $y i32) (result i32)
+  ;; CHECK-NEXT:  (local $2 i32)
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (local.tee $2
+  ;; CHECK-NEXT:    (local.get $y)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (local.get $2)
+  ;; CHECK-NEXT: )
+  (func $extract-make-2 (param $x i32) (param $y i32) (result i32)
+    ;; As above, but the second lane.
+    (tuple.extract 1
+      (tuple.make
+        (local.get $x)
+        (local.get $y)
+      )
+    )
+  )
+
+  ;; CHECK:      (func $extract-make-unreachable (param $x i32) (param $y i32) (result i32)
+  ;; CHECK-NEXT:  (tuple.extract 0
+  ;; CHECK-NEXT:   (tuple.make
+  ;; CHECK-NEXT:    (unreachable)
+  ;; CHECK-NEXT:    (local.get $y)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT: )
+  (func $extract-make-unreachable (param $x i32) (param $y i32) (result i32)
+    (tuple.extract 0
+      (tuple.make
+        (unreachable) ;; because of this we should do nothing
+        (local.get $y)
+      )
+    )
+  )
 )