[RewriteStatepointsForGC] Fix a relocation bug w.r.t values defined by invoke instructions

RewriteStatepointsForGC pass emits an alloca for each GC pointer which will be relocated. It then inserts stores after def and all relocations, and inserts loads before each use as well. In the end, mem2reg is used to update IR with relocations in SSA form.

However, there is a problem with inserting stores for values defined by invoke instructions. The code didn't expect a def was a terminator instruction, and inserting instructions after these terminators resulted in malformed IR.

This patch fixes this problem by handling invoke instructions as a special case. If the def is an invoke instruction, the store will be inserted at the beginning of the normal destination block. Since return value from invoke instruction does not dominate the unwind destination block, no action is needed there.

Patch by: Chen Li
Differential Revision: http://reviews.llvm.org/D7923

llvm-svn: 231183

1 files changed, 12 insertions, 2 deletions

diff --git a/llvm/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp b/llvm/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
index c7d9263158d..ed8029b8a37 100644
--- a/llvm/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
+++ b/llvm/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
@@ -1593,8 +1593,18 @@ static void relocationViaAlloca(
     // store must be inserted after load, otherwise store will be in alloca's
     // use list and an extra load will be inserted before it
     StoreInst *store = new StoreInst(def, alloca);
-    if (isa<Instruction>(def)) {
-      store->insertAfter(cast<Instruction>(def));
+    if (Instruction *inst = dyn_cast<Instruction>(def)) {
+      if (InvokeInst *invoke = dyn_cast<InvokeInst>(inst)) {
+        // InvokeInst is a TerminatorInst so the store need to be inserted
+        // into its normal destination block.
+        BasicBlock *normalDest = invoke->getNormalDest();
+        store->insertBefore(normalDest->getFirstNonPHI());
+      } else {
+        assert(!inst->isTerminator() &&
+               "The only TerminatorInst that can produce a value is "
+               "InvokeInst which is handled above.");
+         store->insertAfter(inst);
+      }
     } else {
       assert((isa<Argument>(def) || isa<GlobalVariable>(def) ||
               (isa<Constant>(def) && cast<Constant>(def)->isNullValue())) &&