Update llvm/clang to trunk r126547.

There are several bugfixes in this update, but the most important one is
to ensure __start_ and __stop_ symbols for linker sets and kernel module
metadata are always emitted in object files:

  http://llvm.org/bugs/show_bug.cgi?id=9292

Before this fix, if you compiled kernel modules with clang, they would
not be properly processed by kldxref, and if they had any dependencies,
the kernel would fail to load those.  Another problem occurred when
attempting to mount a tmpfs filesystem, which would result in 'operation
not supported by device'.

1 files changed, 15 insertions, 8 deletions

diff --git a/contrib/llvm/lib/Transforms/Scalar/LoopDeletion.cpp b/contrib/llvm/lib/Transforms/Scalar/LoopDeletion.cpp
index 6d1d344..753a558 100644
--- a/contrib/llvm/lib/Transforms/Scalar/LoopDeletion.cpp
+++ b/contrib/llvm/lib/Transforms/Scalar/LoopDeletion.cpp
@@ -78,7 +78,6 @@ bool LoopDeletion::IsLoopDead(Loop* L,
                               SmallVector<BasicBlock*, 4>& exitingBlocks,
                               SmallVector<BasicBlock*, 4>& exitBlocks,
                               bool &Changed, BasicBlock *Preheader) {
-  BasicBlock* exitingBlock = exitingBlocks[0];
   BasicBlock* exitBlock = exitBlocks[0];
   
   // Make sure that all PHI entries coming from the loop are loop invariant.
@@ -88,11 +87,21 @@ bool LoopDeletion::IsLoopDead(Loop* L,
   // of the loop.
   BasicBlock::iterator BI = exitBlock->begin();
   while (PHINode* P = dyn_cast<PHINode>(BI)) {
-    Value* incoming = P->getIncomingValueForBlock(exitingBlock);
+    Value* incoming = P->getIncomingValueForBlock(exitingBlocks[0]);
+
+    // Make sure all exiting blocks produce the same incoming value for the exit
+    // block.  If there are different incoming values for different exiting
+    // blocks, then it is impossible to statically determine which value should
+    // be used.
+    for (unsigned i = 1; i < exitingBlocks.size(); ++i) {
+      if (incoming != P->getIncomingValueForBlock(exitingBlocks[i]))
+        return false;
+    }
+      
     if (Instruction* I = dyn_cast<Instruction>(incoming))
       if (!L->makeLoopInvariant(I, Changed, Preheader->getTerminator()))
         return false;
-      
+
     ++BI;
   }
   
@@ -147,10 +156,6 @@ bool LoopDeletion::runOnLoop(Loop* L, LPPassManager& LPM) {
   if (exitBlocks.size() != 1)
     return false;
   
-  // Loops with multiple exits are too complicated to handle correctly.
-  if (exitingBlocks.size() != 1)
-    return false;
-  
   // Finally, we have to check that the loop really is dead.
   bool Changed = false;
   if (!IsLoopDead(L, exitingBlocks, exitBlocks, Changed, preheader))
@@ -166,7 +171,6 @@ bool LoopDeletion::runOnLoop(Loop* L, LPPassManager& LPM) {
   // Now that we know the removal is safe, remove the loop by changing the
   // branch from the preheader to go to the single exit block.  
   BasicBlock* exitBlock = exitBlocks[0];
-  BasicBlock* exitingBlock = exitingBlocks[0];
   
   // Because we're deleting a large chunk of code at once, the sequence in which
   // we remove things is very important to avoid invalidation issues.  Don't
@@ -183,9 +187,12 @@ bool LoopDeletion::runOnLoop(Loop* L, LPPassManager& LPM) {
 
   // Rewrite phis in the exit block to get their inputs from
   // the preheader instead of the exiting block.
+  BasicBlock* exitingBlock = exitingBlocks[0];
   BasicBlock::iterator BI = exitBlock->begin();
   while (PHINode* P = dyn_cast<PHINode>(BI)) {
     P->replaceUsesOfWith(exitingBlock, preheader);
+    for (unsigned i = 1; i < exitingBlocks.size(); ++i)
+      P->removeIncomingValue(exitingBlocks[i]);
     ++BI;
   }