Change how PHINodes store their operands.

Change PHINodes to store simple pointers to their incoming basic blocks,
instead of full-blown Uses.

Note that this loses an optimization in SplitCriticalEdge(), because we
can no longer walk the use list of a BasicBlock to find phi nodes. See
the comment I removed starting "However, the foreach loop is slow for
blocks with lots of predecessors".

Extend replaceAllUsesWith() on a BasicBlock to also update any phi
nodes in the block's successors. This mimics what would have happened
when PHINodes were proper Users of their incoming blocks. (Note that
this only works if OldBB->replaceAllUsesWith(NewBB) is called when
OldBB still has a terminator instruction, so it still has some
successors.)


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@133435 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 14 insertions, 0 deletions

diff --git a/lib/Transforms/Utils/ValueMapper.cpp b/lib/Transforms/Utils/ValueMapper.cpp
index a73bf04..de6cbdc 100644
--- a/lib/Transforms/Utils/ValueMapper.cpp
+++ b/lib/Transforms/Utils/ValueMapper.cpp
@@ -16,6 +16,7 @@
 #include "llvm/Type.h"
 #include "llvm/Constants.h"
 #include "llvm/Function.h"
+#include "llvm/Instructions.h"
 #include "llvm/Metadata.h"
 #include "llvm/ADT/SmallVector.h"
 using namespace llvm;
@@ -128,6 +129,19 @@ void llvm::RemapInstruction(Instruction *I, ValueToValueMapTy &VMap,
              "Referenced value not in value map!");
   }
 
+  // Remap phi nodes' incoming blocks.
+  if (PHINode *PN = dyn_cast<PHINode>(I)) {
+    for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
+      Value *V = MapValue(PN->getIncomingBlock(i), VMap, Flags);
+      // If we aren't ignoring missing entries, assert that something happened.
+      if (V != 0)
+        PN->setIncomingBlock(i, cast<BasicBlock>(V));
+      else
+        assert((Flags & RF_IgnoreMissingEntries) &&
+               "Referenced block not in value map!");
+    }
+  }
+
   // Remap attached metadata.
   SmallVector<std::pair<unsigned, MDNode *>, 4> MDs;
   I->getAllMetadata(MDs);