Merge pull request #37430 from JuliaLang/vc/phi_late-gc

[LateGCLowering] Look through Phi node

Author: vchuravy

src/llvm-late-gc-lowering.cpp

@@ -1458,7 +1458,33 @@ State LateLowerGCFrame::LocalScan(Function &F) {
                                     S.ArrayAllocas[SRet] = tracked.count * cast<ConstantInt>(SRet->getArraySize())->getZExtValue();
                                 }
                                 else {
-                                    AllocaInst *SRet_gc = dyn_cast<AllocaInst>((CI->arg_begin()[1])->stripInBoundsOffsets());
+                                    Value *arg1 = (CI->arg_begin()[1])->stripInBoundsOffsets();
+                                    AllocaInst *SRet_gc = nullptr;
+                                    if (PHINode *Phi = dyn_cast<PHINode>(arg1)) {
+                                        for (Value *V : Phi->incoming_values()) {
+                                            if (AllocaInst *Alloca = dyn_cast<AllocaInst>(V->stripInBoundsOffsets())) {
+                                                if (SRet_gc == nullptr) {
+                                                    SRet_gc = Alloca;
+                                                } else if (SRet_gc == Alloca) {
+                                                    continue;
+                                                } else {
+                                                    llvm_dump(Alloca);
+                                                    llvm_dump(SRet_gc);
+                                                    assert(false && "Allocas in Phi node should match");
+                                                }
+                                            } else {
+                                                llvm_dump(V->stripInBoundsOffsets());
+                                                assert(false && "Expected alloca");
+                                            }
+                                        }
+                                    } else {
+                                        SRet_gc = dyn_cast<AllocaInst>(arg1);
+                                    }
+                                    if (!SRet_gc) {
+                                        llvm_dump(CI);
+                                        llvm_dump(arg1);
+                                        assert(false && "Expected alloca");
+                                    }
                                     Type *ElT = SRet_gc->getAllocatedType();
                                     if (!(SRet_gc->isStaticAlloca() && isa<PointerType>(ElT) && ElT->getPointerAddressSpace() == AddressSpace::Tracked)) {
                                         S.ArrayAllocas[SRet_gc] = tracked.count * cast<ConstantInt>(SRet_gc->getArraySize())->getZExtValue();