End the current basic block on a Call (#5823)

Before this PR, if a call had no paths to a catch in the same function then we skipped
creating a new basic block right after it. As a result, we could have a call in the middle
of a basic block. If EH is enabled that means we might transfer control flow out of
the function from the middle of a block. But it is better to have the property that
any transfer of control flow - to another basic block, or outside of the function - can
only happen at the end of a basic block.

This causes some overhead, but a subsequent PR (#5838) will remove that as a
followup, and this PR adds a little code to pass the module and check if EH is enabled,
and avoid the overhead if not, which at least avoids regressing the non-EH case
until that followup lands.

1 files changed, 45 insertions, 0 deletions

diff --git a/test/gtest/cfg.cpp b/test/gtest/cfg.cpp
index 03e333965..7bf18ebdb 100644
--- a/test/gtest/cfg.cpp
+++ b/test/gtest/cfg.cpp
@@ -87,6 +87,51 @@ TEST_F(CFGTest, Print) {
   EXPECT_EQ(ss.str(), cfgText);
 }
 
+TEST_F(CFGTest, CallBlock) {
+  // Verify that a call instruction ends the current basic block. Even if the
+  // call has no control flow edges inside the function (no catches it can
+  // reach), we still end a basic block with the call, so that we preserve the
+  // property of basic blocks ending in possibly-control-flow-transferring
+  // instructions.
+  auto moduleText = R"wasm(
+    (module
+      (func $foo
+        (drop
+          (i32.const 0)
+        )
+        (call $bar)
+        (drop
+          (i32.const 1)
+        )
+      )
+      (func $bar)
+    )
+  )wasm";
+
+  auto cfgText = R"cfg(;; preds: [], succs: [1]
+0:
+  0: i32.const 0
+  1: drop
+  2: call $bar
+
+;; preds: [0], succs: []
+1:
+  3: i32.const 1
+  4: drop
+  5: block
+)cfg";
+
+  Module wasm;
+  parseWast(wasm, moduleText);
+
+  CFG cfg = CFG::fromFunction(wasm.getFunction("foo"));
+
+  std::stringstream ss;
+  cfg.print(ss);
+
+  EXPECT_EQ(ss.str(), cfgText);
+}
+
 TEST_F(CFGTest, LinearLiveness) {
   auto moduleText = R"wasm(
     (module