[llvm] r258409 - [BlockPlacement] Add option to align all non-fall-through blocks.

[Geoff Berry via llvm-commits]

Author: gberry
Date: Thu Jan 21 11:25:52 2016
New Revision: 258409

URL: http://llvm.org/viewvc/llvm-project?rev=258409&view=rev
Log:
[BlockPlacement] Add option to align all non-fall-through blocks.

Summary: This option is being added for testing purposes.

Reviewers: mcrosier

Subscribers: mcrosier, llvm-commits

Differential Revision: http://reviews.llvm.org/D16410

Modified:
    llvm/trunk/lib/CodeGen/MachineBlockPlacement.cpp

Modified: llvm/trunk/lib/CodeGen/MachineBlockPlacement.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/MachineBlockPlacement.cpp?rev=258409&r1=258408&r2=258409&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/MachineBlockPlacement.cpp (original)
+++ llvm/trunk/lib/CodeGen/MachineBlockPlacement.cpp Thu Jan 21 11:25:52 2016
@@ -62,6 +62,13 @@ static cl::opt<unsigned> AlignAllBlock("
                                                 "blocks in the function."),
                                        cl::init(0), cl::Hidden);
 
+static cl::opt<unsigned> AlignAllNonFallThruBlocks(
+    "align-all-nofallthru-blocks",
+    cl::desc("Force the alignment of all "
+             "blocks that have no fall-through predecessors (i.e. don't add "
+             "nops that are executed)."),
+    cl::init(0), cl::Hidden);
+
 static cl::opt<unsigned>
     AlignAllLoops("align-all-loops",
                   cl::desc("Force the alignment of all loops in the function."),
@@ -1405,6 +1412,15 @@ bool MachineBlockPlacement::runOnMachine
     // Align all of the blocks in the function to a specific alignment.
     for (MachineBasicBlock &MBB : F)
       MBB.setAlignment(AlignAllBlock);
+  else if (AlignAllNonFallThruBlocks) {
+    // Align all of the blocks that have no fall-through predecessors to a
+    // specific alignment.
+    for (auto MBI = std::next(F.begin()), MBE = F.end(); MBI != MBE; ++MBI) {
+      auto LayoutPred = std::prev(MBI);
+      if (!LayoutPred->isSuccessor(&*MBI))
+        MBI->setAlignment(AlignAllNonFallThruBlocks);
+    }
+  }
 
   // We always return true as we have no way to track whether the final order
   // differs from the original order.