Create HandlePHINodesInSuccessorBlocksFast, a version of
HandlePHINodesInSuccessorBlocks that works FastISel-style. This
allows PHI nodes to be updated correctly while using FastISel.
This also involves some code reorganization; ValueMap and
MBBMap are now members of the FastISel class, so they needn't
be passed around explicitly anymore. Also, SelectInstructions
is changed to SelectInstruction, and only does one instruction
at a time.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@55746 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp
index 9df4bba..3bbcdc9 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp
@@ -4757,9 +4757,64 @@
}
}
SDL->ConstantsOut.clear();
-
- // Lower the terminator after the copies are emitted.
- SDL->visit(*LLVMBB->getTerminator());
}
+/// This is the Fast-ISel version of HandlePHINodesInSuccessorBlocks. It only
+/// supports legal types, and it emits MachineInstrs directly instead of
+/// creating SelectionDAG nodes.
+///
+bool
+SelectionDAGISel::HandlePHINodesInSuccessorBlocksFast(BasicBlock *LLVMBB,
+ FastISel *F) {
+ TerminatorInst *TI = LLVMBB->getTerminator();
+ SmallPtrSet<MachineBasicBlock *, 4> SuccsHandled;
+ unsigned OrigNumPHINodesToUpdate = SDL->PHINodesToUpdate.size();
+
+ // Check successor nodes' PHI nodes that expect a constant to be available
+ // from this block.
+ for (unsigned succ = 0, e = TI->getNumSuccessors(); succ != e; ++succ) {
+ BasicBlock *SuccBB = TI->getSuccessor(succ);
+ if (!isa<PHINode>(SuccBB->begin())) continue;
+ MachineBasicBlock *SuccMBB = FuncInfo->MBBMap[SuccBB];
+
+ // If this terminator has multiple identical successors (common for
+ // switches), only handle each succ once.
+ if (!SuccsHandled.insert(SuccMBB)) continue;
+
+ MachineBasicBlock::iterator MBBI = SuccMBB->begin();
+ PHINode *PN;
+
+ // At this point we know that there is a 1-1 correspondence between LLVM PHI
+ // nodes and Machine PHI nodes, but the incoming operands have not been
+ // emitted yet.
+ for (BasicBlock::iterator I = SuccBB->begin();
+ (PN = dyn_cast<PHINode>(I)); ++I) {
+ // Ignore dead phi's.
+ if (PN->use_empty()) continue;
+
+ // Only handle legal types. Two interesting things to note here. First,
+ // by bailing out early, we may leave behind some dead instructions,
+ // since SelectionDAG's HandlePHINodesInSuccessorBlocks will insert its
+ // own moves. Second, this check is necessary becuase FastISel doesn't
+ // use CreateRegForValue to create registers, so it always creates
+ // exactly one register for each non-void instruction.
+ MVT VT = TLI.getValueType(PN->getType(), /*AllowUnknown=*/true);
+ if (VT == MVT::Other || !TLI.isTypeLegal(VT)) {
+ SDL->PHINodesToUpdate.resize(OrigNumPHINodesToUpdate);
+ return false;
+ }
+
+ Value *PHIOp = PN->getIncomingValueForBlock(LLVMBB);
+
+ unsigned Reg = F->getRegForValue(PHIOp);
+ if (Reg == 0) {
+ SDL->PHINodesToUpdate.resize(OrigNumPHINodesToUpdate);
+ return false;
+ }
+ SDL->PHINodesToUpdate.push_back(std::make_pair(MBBI++, Reg));
+ }
+ }
+
+ return true;
+}