[llvm-commits] [llvm] r140173 - /llvm/trunk/lib/Transforms/IPO/LoopExtractor.cpp

[Bill Wendling]

Author: void
Date: Tue Sep 20 14:10:24 2011
New Revision: 140173

URL: http://llvm.org/viewvc/llvm-project?rev=140173&view=rev
Log:
When extracting a basic block that ends in an 'invoke' instruction, we need to
extract its associated landing pad block as well. However, that landing pad
block may have more than one predecessor. So split the landing pad block so that
individual landing pads have only one predecessor.

This type of transformation may produce a false positive with bugpoint.

Modified:
    llvm/trunk/lib/Transforms/IPO/LoopExtractor.cpp

Modified: llvm/trunk/lib/Transforms/IPO/LoopExtractor.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/IPO/LoopExtractor.cpp?rev=140173&r1=140172&r2=140173&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/IPO/LoopExtractor.cpp (original)
+++ llvm/trunk/lib/Transforms/IPO/LoopExtractor.cpp Tue Sep 20 14:10:24 2011
@@ -23,6 +23,7 @@
 #include "llvm/Analysis/LoopPass.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Transforms/Scalar.h"
+#include "llvm/Transforms/Utils/BasicBlockUtils.h"
 #include "llvm/Transforms/Utils/FunctionUtils.h"
 #include "llvm/ADT/Statistic.h"
 #include <fstream>
@@ -53,12 +54,12 @@
 
 char LoopExtractor::ID = 0;
 INITIALIZE_PASS_BEGIN(LoopExtractor, "loop-extract",
-                "Extract loops into new functions", false, false)
+                      "Extract loops into new functions", false, false)
 INITIALIZE_PASS_DEPENDENCY(BreakCriticalEdges)
 INITIALIZE_PASS_DEPENDENCY(LoopSimplify)
 INITIALIZE_PASS_DEPENDENCY(DominatorTree)
 INITIALIZE_PASS_END(LoopExtractor, "loop-extract",
-                "Extract loops into new functions", false, false)
+                    "Extract loops into new functions", false, false)
 
 namespace {
   /// SingleLoopExtractor - For bugpoint.
@@ -149,6 +150,7 @@
   /// BlocksToNotExtract list.
   class BlockExtractorPass : public ModulePass {
     void LoadFile(const char *Filename);
+    void SplitLandingPadPreds(Function *F);
 
     std::vector<BasicBlock*> BlocksToNotExtract;
     std::vector<std::pair<std::string, std::string> > BlocksToNotExtractByName;
@@ -171,8 +173,7 @@
 // createBlockExtractorPass - This pass extracts all blocks (except those
 // specified in the argument list) from the functions in the module.
 //
-ModulePass *llvm::createBlockExtractorPass()
-{
+ModulePass *llvm::createBlockExtractorPass() {
   return new BlockExtractorPass();
 }
 
@@ -194,6 +195,37 @@
   }
 }
 
+/// SplitLandingPadPreds - The landing pad needs to be extracted with the invoke
+/// instruction. The critical edge breaker will refuse to break critical edges
+/// to a landing pad. So do them here. After this method runs, all landing pads
+/// should have only one predecessor.
+void BlockExtractorPass::SplitLandingPadPreds(Function *F) {
+  for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) {
+    InvokeInst *II = dyn_cast<InvokeInst>(I);
+    if (!II) continue;
+    BasicBlock *Parent = II->getParent();
+    BasicBlock *LPad = II->getUnwindDest();
+
+    // Look through the landing pad's predecessors. If one of them ends in an
+    // 'invoke', then we want to split the landing pad.
+    bool Split = false;
+    for (pred_iterator
+           PI = pred_begin(LPad), PE = pred_end(LPad); PI != PE; ++PI) {
+      BasicBlock *BB = *PI;
+      if (BB->isLandingPad() && BB != Parent &&
+          isa<InvokeInst>(Parent->getTerminator())) {
+        Split = true;
+        break;
+      }
+    }
+
+    if (!Split) continue;
+
+    SmallVector<BasicBlock*, 2> NewBBs;
+    SplitLandingPadPredecessors(LPad, Parent, ".1", ".2", 0, NewBBs);
+  }
+}
+
 bool BlockExtractorPass::runOnModule(Module &M) {
   std::set<BasicBlock*> TranslatedBlocksToNotExtract;
   for (unsigned i = 0, e = BlocksToNotExtract.size(); i != e; ++i) {
@@ -236,13 +268,20 @@
   // Now that we know which blocks to not extract, figure out which ones we WANT
   // to extract.
   std::vector<BasicBlock*> BlocksToExtract;
-  for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F)
+  for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F) {
+    SplitLandingPadPreds(&*F);
     for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
       if (!TranslatedBlocksToNotExtract.count(BB))
         BlocksToExtract.push_back(BB);
+  }
 
-  for (unsigned i = 0, e = BlocksToExtract.size(); i != e; ++i)
-    ExtractBasicBlock(BlocksToExtract[i]);
+  for (unsigned i = 0, e = BlocksToExtract.size(); i != e; ++i) {
+    SmallVector<BasicBlock*, 2> BlocksToExtractVec;
+    BlocksToExtractVec.push_back(BlocksToExtract[i]);
+    if (const InvokeInst *II = dyn_cast<InvokeInst>(BlocksToExtract[i]))
+      BlocksToExtractVec.push_back(II->getUnwindDest());
+    ExtractBasicBlock(BlocksToExtractVec);
+  }
 
   return !BlocksToExtract.empty();
 }