Fix bug and leak in relooper merge consecutive blocks (#2159)

Fixes in Relooper merge consecutive blocks:

    Entry block getting removed when it is part of a loop:

bb1->AddBranchTo(bb2, nullptr);
bb1->AddBranchTo(bb3, ...);
bb2->AddBranchTo(bb1, nullptr);
bb3->AddBranchTo(bb4, nullptr);
relooper.AddBlock(bb1);
relooper.AddBlock(bb2);
relooper.AddBlock(bb3);
relooper.AddBlock(bb4);
relooper.Calculate(bb1);

    Branches memory leak

1 files changed, 49 insertions, 0 deletions

diff --git a/test/example/relooper-merge7.c b/test/example/relooper-merge7.c
new file mode 100644
index 000000000..c942e3b25
--- /dev/null
+++ b/test/example/relooper-merge7.c
@@ -0,0 +1,49 @@
+
+#include <assert.h>
+#include <stdio.h>
+
+#include "binaryen-c.h"
+
+int main() {
+  BinaryenModuleRef module = BinaryenModuleCreate();
+
+  RelooperRef relooper = RelooperCreate(module);
+
+  // Create the basic blocks
+  RelooperBlockRef b[4];
+  int hasTerminator[4] = {0, 0, 0, 1};
+
+  int numBlocks = sizeof(b) / sizeof(RelooperBlockRef);
+  assert(sizeof(hasTerminator) / sizeof(int) == numBlocks);
+  int i;
+  for (i = 0; i < numBlocks; i++) {
+    BinaryenExpressionRef args[] = {
+      BinaryenConst(module, BinaryenLiteralInt32(i))};
+    BinaryenExpressionRef list[] = {
+      BinaryenCall(module, "print", args, 1, BinaryenTypeNone()),
+      BinaryenReturn(module, NULL) // relevant only if hasTerminator[i]
+    };
+    b[i] = RelooperAddBlock(
+      relooper,
+      BinaryenBlock(
+        module, NULL, list, 1 + hasTerminator[i], BinaryenTypeNone()));
+  }
+
+  // Create the branches.
+  // In this testcase, only b[2] and b[3] can be merged.
+  RelooperAddBranch(b[0], b[1], NULL, NULL);
+  RelooperAddBranch(
+    b[0], b[2], BinaryenConst(module, BinaryenLiteralInt32(-10)), NULL);
+  RelooperAddBranch(b[1], b[0], NULL, NULL);
+  RelooperAddBranch(b[2], b[3], NULL, NULL);
+
+  BinaryenExpressionRef all = RelooperRenderAndDispose(relooper, b[0], 1);
+
+  // Print it out
+  BinaryenExpressionPrint(all);
+
+  // Clean up the module, which owns all the objects we created above
+  BinaryenModuleDispose(module);
+
+  return 0;
+}