ConstraintAnalysis: Handle tees (#8998)

src/ir/constraint.cpp

diff --git a/src/ir/constraint.cpp b/src/ir/constraint.cpp
index 0d30545..a151628 100644
--- a/src/ir/constraint.cpp
+++ b/src/ir/constraint.cpp
@@ -544,6 +544,10 @@
     set(index, Constraint{Abstract::Eq, {get->index}});
     return;
   }
+  if (auto* tee = value->dynCast<LocalSet>()) {
+    set(index, Constraint{Abstract::Eq, {tee->index}});
+    return;
+  }
 
   // Apply an increment of a local, x = y + 1.
   Index y;

test/lit/passes/constraint-analysis.wast

diff --git a/test/lit/passes/constraint-analysis.wast b/test/lit/passes/constraint-analysis.wast
index 0f9a7f0..8325cd8 100644
--- a/test/lit/passes/constraint-analysis.wast
+++ b/test/lit/passes/constraint-analysis.wast
@@ -4555,4 +4555,57 @@
       )
     )
   )
+
+  ;; CHECK:      (func $tee (type $1)
+  ;; CHECK-NEXT:  (local $x i32)
+  ;; CHECK-NEXT:  (local $y i32)
+  ;; CHECK-NEXT:  (local.set $x
+  ;; CHECK-NEXT:   (local.tee $y
+  ;; CHECK-NEXT:    (i32.const 10)
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (i32.const 1)
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (i32.const 1)
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT: )
+  ;; OPTIN:      (func $tee (type $1)
+  ;; OPTIN-NEXT:  (local $x i32)
+  ;; OPTIN-NEXT:  (local $y i32)
+  ;; OPTIN-NEXT:  (local.set $x
+  ;; OPTIN-NEXT:   (local.tee $y
+  ;; OPTIN-NEXT:    (i32.const 10)
+  ;; OPTIN-NEXT:   )
+  ;; OPTIN-NEXT:  )
+  ;; OPTIN-NEXT:  (drop
+  ;; OPTIN-NEXT:   (i32.const 1)
+  ;; OPTIN-NEXT:  )
+  ;; OPTIN-NEXT:  (drop
+  ;; OPTIN-NEXT:   (i32.const 1)
+  ;; OPTIN-NEXT:  )
+  ;; OPTIN-NEXT: )
+  (func $tee
+    ;; We can read values through tees.
+    (local $x i32)
+    (local $y i32)
+    (local.set $x
+      (local.tee $y
+        (i32.const 10)
+      )
+    )
+    (drop
+      (i32.eq
+        (local.get $x)
+        (i32.const 10)
+      )
+    )
+    (drop
+      (i32.eq
+        (local.get $y)
+        (i32.const 10)
+      )
+    )
+  )
 )