[PATCH] D16410: [BlockPlacement] Add option to align all non-fall-through blocks.

[Geoff Berry via llvm-commits]

gberry created this revision.
gberry added a reviewer: mcrosier.
gberry added a subscriber: llvm-commits.
Herald added a subscriber: mcrosier.

This option is being added for testing purposes.

http://reviews.llvm.org/D16410

Files:
  lib/CodeGen/MachineBlockPlacement.cpp

Index: lib/CodeGen/MachineBlockPlacement.cpp
===================================================================
--- lib/CodeGen/MachineBlockPlacement.cpp
+++ lib/CodeGen/MachineBlockPlacement.cpp
@@ -62,6 +62,13 @@
                                                 "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 @@
     // 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.


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