Properly handle side-effects when removing switch statements

Signed-off-by: Mihai Budiu <mbudiu@vmware.com>
p4lang · Oct 28, 2022 · dcd7656 · dcd7656
1 parent b5980b6
commit dcd7656
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Showing 7 changed files with 65 additions and 5 deletions.
diff --git a/frontends/p4/simplify.cpp b/frontends/p4/simplify.cpp
@@ -94,12 +94,15 @@ const IR::Node* DoSimplifyControlFlow::postorder(IR::SwitchStatement* statement)
     if (statement->cases.empty()) {
         // If this is a table application remove the switch altogether but keep
         // the table application.  Otherwise remove the switch altogether.
-        if (auto mem = statement->expression->to<IR::Member>()) {
-            if (auto mce = mem->expr->to<IR::MethodCallExpression>()) {
-                LOG2("Removing switch statement " << statement << " keeping " << mce);
-                return new IR::MethodCallStatement(mce->srcInfo, mce);
-            }
+        if (TableApplySolver::isActionRun(statement->expression, refMap, typeMap)) {
+            auto mce = statement->expression->checkedTo<IR::Member>()->
+                    expr->checkedTo<IR::MethodCallExpression>();
+            LOG2("Removing switch statement " << statement << " keeping " << mce);
+            return new IR::MethodCallStatement(statement->srcInfo, mce);
         }
+        if (SideEffects::check(statement->expression, this, refMap, typeMap))
+            // This can happen if this pass is run before SideEffectOrdering.
+            return statement;
         LOG2("Removing switch statement " << statement);
         return nullptr;
     }

diff --git a/testdata/p4_16_samples/issue3619-1.p4 b/testdata/p4_16_samples/issue3619-1.p4
@@ -0,0 +1,15 @@
+bit<4> f(in bit<4> d) {
+    return d;
+}
+
+control c(in bit<4> v) {
+    apply {
+        switch(f(v)) {
+        }
+    }
+}
+
+control C(in bit<4> b);
+package top(C c);
+
+top(c()) main;
diff --git a/testdata/p4_16_samples_outputs/issue3619-1-first.p4 b/testdata/p4_16_samples_outputs/issue3619-1-first.p4
@@ -0,0 +1,13 @@
+bit<4> f(in bit<4> d) {
+    return d;
+}
+control c(in bit<4> v) {
+    apply {
+        switch (f(v)) {
+        }
+    }
+}
+
+control C(in bit<4> b);
+package top(C c);
+top(c()) main;
diff --git a/testdata/p4_16_samples_outputs/issue3619-1-frontend.p4 b/testdata/p4_16_samples_outputs/issue3619-1-frontend.p4
@@ -0,0 +1,8 @@
+control c(in bit<4> v) {
+    apply {
+    }
+}
+
+control C(in bit<4> b);
+package top(C c);
+top(c()) main;
diff --git a/testdata/p4_16_samples_outputs/issue3619-1-midend.p4 b/testdata/p4_16_samples_outputs/issue3619-1-midend.p4
@@ -0,0 +1,8 @@
+control c(in bit<4> v) {
+    apply {
+    }
+}
+
+control C(in bit<4> b);
+package top(C c);
+top(c()) main;
diff --git a/testdata/p4_16_samples_outputs/issue3619-1.p4 b/testdata/p4_16_samples_outputs/issue3619-1.p4
@@ -0,0 +1,13 @@
+bit<4> f(in bit<4> d) {
+    return d;
+}
+control c(in bit<4> v) {
+    apply {
+        switch (f(v)) {
+        }
+    }
+}
+
+control C(in bit<4> b);
+package top(C c);
+top(c()) main;
diff --git a/testdata/p4_16_samples_outputs/issue3619-1.p4-stderr b/testdata/p4_16_samples_outputs/issue3619-1.p4-stderr