Properly handle the mftb instruction.

[oota-llvm.git] / lib / Target / PowerPC / PPCBranchSelector.cpp

diff --git a/lib/Target/PowerPC/PPCBranchSelector.cpp b/lib/Target/PowerPC/PPCBranchSelector.cpp
index 3dd19d03e8b59a0d9691283c2709ac9fbb09037d..940d55ac1f36e68cb0a29c5f7bf8ecc8ee9e6bc1 100644 (file)
--- a/lib/Target/PowerPC/PPCBranchSelector.cpp
+++ b/lib/Target/PowerPC/PPCBranchSelector.cpp
@@ -64,18 +64,43 @@ FunctionPass *llvm::createPPCBranchSelectionPass() {
 }
 
 bool PPCBSel::runOnMachineFunction(MachineFunction &Fn) {
-  const PPCInstrInfo *TII = static_cast<const PPCInstrInfo *>(
-      Fn.getTarget().getSubtargetImpl()->getInstrInfo());
+  const PPCInstrInfo *TII =
+      static_cast<const PPCInstrInfo *>(Fn.getSubtarget().getInstrInfo());
   // Give the blocks of the function a dense, in-order, numbering.
   Fn.RenumberBlocks();
   BlockSizes.resize(Fn.getNumBlockIDs());
 
+  auto GetAlignmentAdjustment =
+    [TII](MachineBasicBlock &MBB, unsigned Offset) -> unsigned {
+    unsigned Align = MBB.getAlignment();
+    if (!Align)
+      return 0;
+
+    unsigned AlignAmt = 1 << Align;
+    unsigned ParentAlign = MBB.getParent()->getAlignment();
+
+    if (Align <= ParentAlign)
+      return OffsetToAlignment(Offset, AlignAmt);
+
+    // The alignment of this MBB is larger than the function's alignment, so we
+    // can't tell whether or not it will insert nops. Assume that it will.
+    return AlignAmt + OffsetToAlignment(Offset, AlignAmt);
+  };
+
   // Measure each MBB and compute a size for the entire function.
   unsigned FuncSize = 0;
   for (MachineFunction::iterator MFI = Fn.begin(), E = Fn.end(); MFI != E;
        ++MFI) {
     MachineBasicBlock *MBB = MFI;
 
+    // The end of the previous block may have extra nops if this block has an
+    // alignment requirement.
+    if (MBB->getNumber() > 0) {
+      unsigned AlignExtra = GetAlignmentAdjustment(*MBB, FuncSize);
+      BlockSizes[MBB->getNumber()-1] += AlignExtra;
+      FuncSize += AlignExtra;
+    }
+
     unsigned BlockSize = 0;
     for (MachineBasicBlock::iterator MBBI = MBB->begin(), EE = MBB->end();
          MBBI != EE; ++MBBI)