[PATCH] D31681: [ExecutionDepsFix] Don't recurse over the CFG

[Keno Fischer via Phabricator via llvm-commits]

loladiro created this revision.

Use an explicit std::vector instead, to avoid accidentally causing stack overflows
for input with very large CFGs.


https://reviews.llvm.org/D31681

Files:
  include/llvm/CodeGen/ExecutionDepsFix.h
  lib/CodeGen/ExecutionDepsFix.cpp


Index: lib/CodeGen/ExecutionDepsFix.cpp
===================================================================
--- lib/CodeGen/ExecutionDepsFix.cpp
+++ lib/CodeGen/ExecutionDepsFix.cpp
@@ -616,7 +616,9 @@
          MBBInfos[MBB].IncomingProcessed == MBB->pred_size();
 }
 
-void ExecutionDepsFix::updateSuccessors(MachineBasicBlock *MBB, bool Primary) {
+void ExecutionDepsFix::updateSuccessors(
+    std::vector<MachineBasicBlock *> &ToRevisit, MachineBasicBlock *MBB,
+    bool Primary) {
   bool Done = isBlockDone(MBB);
   for (auto *Succ : MBB->successors()) {
     if (!isBlockDone(Succ)) {
@@ -627,10 +629,7 @@
         MBBInfos[Succ].IncomingCompleted++;
       }
       if (isBlockDone(Succ)) {
-        // Perform secondary processing for this successor. See the big comment
-        // in runOnMachineFunction, for an explanation of the iteration order.
-        processBasicBlock(Succ, false);
-        updateSuccessors(Succ, false);
+        ToRevisit.push_back(Succ);
       }
     }
   }
@@ -708,15 +707,22 @@
 
   MachineBasicBlock *Entry = &*MF->begin();
   ReversePostOrderTraversal<MachineBasicBlock*> RPOT(Entry);
+  std::vector<MachineBasicBlock *> ToRevisit;
   for (ReversePostOrderTraversal<MachineBasicBlock*>::rpo_iterator
          MBBI = RPOT.begin(), MBBE = RPOT.end(); MBBI != MBBE; ++MBBI) {
     MachineBasicBlock *MBB = *MBBI;
     // N.B: IncomingProcessed and IncomingCompleted were already updated while
     // processing this block's predecessors.
     MBBInfos[MBB].PrimaryCompleted = true;
     MBBInfos[MBB].PrimaryIncoming = MBBInfos[MBB].IncomingProcessed;
     processBasicBlock(MBB, true);
-    updateSuccessors(MBB, true);
+    updateSuccessors(ToRevisit, MBB, true);
+    while (!ToRevisit.empty()) {
+      MachineBasicBlock *ToRevisitBB = &*ToRevisit.back();
+      ToRevisit.pop_back();
+      processBasicBlock(ToRevisitBB, false);
+      updateSuccessors(ToRevisit, ToRevisitBB, false);
+    }
   }
 
   // We need to go through again and finalize any blocks that are not done yet.
Index: include/llvm/CodeGen/ExecutionDepsFix.h
===================================================================
--- include/llvm/CodeGen/ExecutionDepsFix.h
+++ include/llvm/CodeGen/ExecutionDepsFix.h
@@ -205,7 +205,8 @@
   void leaveBasicBlock(MachineBasicBlock*);
   bool isBlockDone(MachineBasicBlock *);
   void processBasicBlock(MachineBasicBlock *MBB, bool PrimaryPass);
-  void updateSuccessors(MachineBasicBlock *MBB, bool PrimaryPass);
+  void updateSuccessors(std::vector<MachineBasicBlock *> &ToRevisit,
+                        MachineBasicBlock *MBB, bool PrimaryPass);
   bool visitInstr(MachineInstr *);
   void processDefs(MachineInstr *, bool breakDependency, bool Kill);
   void visitSoftInstr(MachineInstr*, unsigned mask);


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D31681.94129.patch
Type: text/x-patch
Size: 2776 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20170404/d9f7caab/attachment.bin>