[PATCH] D43000: Do not move stores for coroutine allocator args

[Brian Gesiak via Phabricator via llvm-commits]

modocache created this revision.
modocache added reviewers: rsmith, GorNishanov, eric_niebler.

The behavior described in Coroutines TS `[dcl.fct.def.coroutine]/7`
allows coroutine parameters to be passed into allocator functions.
The instructions to store values into the alloca'd parameters must not
be moved past the frame allocation, otherwise uninitialized values are
passed to the allocator.

Test Plan: `check-llvm`


Repository:
  rL LLVM

https://reviews.llvm.org/D43000

Files:
  lib/Transforms/Coroutines/CoroSplit.cpp


Index: lib/Transforms/Coroutines/CoroSplit.cpp
===================================================================
--- lib/Transforms/Coroutines/CoroSplit.cpp
+++ lib/Transforms/Coroutines/CoroSplit.cpp
@@ -654,13 +654,28 @@
   // set.
   do {
     Instruction *Current = Work.pop_back_val();
+    DEBUG(dbgs() << "CoroSplit: Will not relocate:\t" << *Current << "\n");
     DoNotRelocate.insert(Current);
     for (Value *U : Current->operands()) {
       auto *I = dyn_cast<Instruction>(U);
       if (!I)
         continue;
-      if (isa<AllocaInst>(U))
+
+      if (auto *Alloca = dyn_cast<AllocaInst>(I)) {
+        // Stores to alloca instructions that occur before coroutine frame
+        // is allocated should not be moved; the stored values may be used
+        // by the coroutine frame allocator.
+        if (RelocBlocks.count(Alloca->getParent()) != 0) {
+          for (auto AI = Alloca->user_begin(), AE = Alloca->user_end(); AI != AE;
+               ++AI) {
+            if (auto *Store = dyn_cast<llvm::StoreInst>(*AI)) {
+              DoNotRelocate.insert(Store);
+            }
+          }
+        }
         continue;
+      }
+
       if (DoNotRelocate.count(I) == 0) {
         Work.push_back(I);
         DoNotRelocate.insert(I);


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