It's not necessary to do rounding for alloca operations when the requested

alignment is equal to the stack alignment.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@40004 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 81 insertions, 0 deletions

diff --git a/lib/CodeGen/UnreachableBlockElim.cpp b/lib/CodeGen/UnreachableBlockElim.cpp
new file mode 100644
index 0000000..0a611ab
--- /dev/null
+++ b/lib/CodeGen/UnreachableBlockElim.cpp
@@ -0,0 +1,81 @@
+//===-- UnreachableBlockElim.cpp - Remove unreachable blocks for codegen --===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file was developed by the LLVM research group and is distributed under
+// the University of Illinois Open Source License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass is an extremely simple version of the SimplifyCFG pass.  Its sole
+// job is to delete LLVM basic blocks that are not reachable from the entry
+// node.  To do this, it performs a simple depth first traversal of the CFG,
+// then deletes any unvisited nodes.
+//
+// Note that this pass is really a hack.  In particular, the instruction
+// selectors for various targets should just not generate code for unreachable
+// blocks.  Until LLVM has a more systematic way of defining instruction
+// selectors, however, we cannot really expect them to handle additional
+// complexity.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/Constant.h"
+#include "llvm/Instructions.h"
+#include "llvm/Function.h"
+#include "llvm/Pass.h"
+#include "llvm/Type.h"
+#include "llvm/Support/CFG.h"
+#include "llvm/Support/Compiler.h"
+#include "llvm/ADT/DepthFirstIterator.h"
+using namespace llvm;
+
+namespace {
+  class VISIBILITY_HIDDEN UnreachableBlockElim : public FunctionPass {
+    virtual bool runOnFunction(Function &F);
+  public:
+    static char ID; // Pass identification, replacement for typeid
+    UnreachableBlockElim() : FunctionPass((intptr_t)&ID) {}
+  };
+  char UnreachableBlockElim::ID = 0;
+  RegisterPass<UnreachableBlockElim>
+  X("unreachableblockelim", "Remove unreachable blocks from the CFG");
+}
+
+FunctionPass *llvm::createUnreachableBlockEliminationPass() {
+  return new UnreachableBlockElim();
+}
+
+bool UnreachableBlockElim::runOnFunction(Function &F) {
+  std::set<BasicBlock*> Reachable;
+
+  // Mark all reachable blocks.
+  for (df_ext_iterator<Function*> I = df_ext_begin(&F, Reachable),
+         E = df_ext_end(&F, Reachable); I != E; ++I)
+    /* Mark all reachable blocks */;
+
+  // Loop over all dead blocks, remembering them and deleting all instructions
+  // in them.
+  std::vector<BasicBlock*> DeadBlocks;
+  for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
+    if (!Reachable.count(I)) {
+      BasicBlock *BB = I;
+      DeadBlocks.push_back(BB);
+      while (PHINode *PN = dyn_cast<PHINode>(BB->begin())) {
+        PN->replaceAllUsesWith(Constant::getNullValue(PN->getType()));
+        BB->getInstList().pop_front();
+      }
+      for (succ_iterator SI = succ_begin(BB), E = succ_end(BB); SI != E; ++SI)
+        (*SI)->removePredecessor(BB);
+      BB->dropAllReferences();
+    }
+
+  if (DeadBlocks.empty()) return false;
+
+  // Actually remove the blocks now.
+  for (unsigned i = 0, e = DeadBlocks.size(); i != e; ++i)
+    F.getBasicBlockList().erase(DeadBlocks[i]);
+
+  return true;
+}