[llvm-commits] [llvm] r114632 - /llvm/trunk/lib/Target/ARM/ARMBaseInstrInfo.cpp

[Evan Cheng]

Author: evancheng
Date: Thu Sep 23 01:54:40 2010
New Revision: 114632

URL: http://llvm.org/viewvc/llvm-project?rev=114632&view=rev
Log:
If there are multiple unconditional branches terminating a block, eliminate all
but the first one. Those will never be executed. There was logic to do this
but it was faulty.

Modified:
    llvm/trunk/lib/Target/ARM/ARMBaseInstrInfo.cpp

Modified: llvm/trunk/lib/Target/ARM/ARMBaseInstrInfo.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/ARM/ARMBaseInstrInfo.cpp?rev=114632&r1=114631&r2=114632&view=diff
==============================================================================
--- llvm/trunk/lib/Target/ARM/ARMBaseInstrInfo.cpp (original)
+++ llvm/trunk/lib/Target/ARM/ARMBaseInstrInfo.cpp Thu Sep 23 01:54:40 2010
@@ -275,13 +275,29 @@
 
   // Get the instruction before it if it is a terminator.
   MachineInstr *SecondLastInst = I;
+  unsigned SecondLastOpc = SecondLastInst->getOpcode();
+
+  // If AllowModify is true and the block ends with two or more unconditional
+  // branches, delete all but the first unconditional branch.
+  if (AllowModify && isUncondBranchOpcode(LastOpc)) {
+    while (isUncondBranchOpcode(SecondLastOpc)) {
+      LastInst->eraseFromParent();
+      LastInst = SecondLastInst;
+      LastOpc = LastInst->getOpcode();
+      if (I == MBB.begin() || !isUnpredicatedTerminator(--I))
+        break;
+      else {
+        SecondLastInst = I;
+        SecondLastOpc = SecondLastInst->getOpcode();
+      }
+    }
+  }
 
   // If there are three terminators, we don't know what sort of block this is.
   if (SecondLastInst && I != MBB.begin() && isUnpredicatedTerminator(--I))
     return true;
 
   // If the block ends with a B and a Bcc, handle it.
-  unsigned SecondLastOpc = SecondLastInst->getOpcode();
   if (isCondBranchOpcode(SecondLastOpc) && isUncondBranchOpcode(LastOpc)) {
     TBB =  SecondLastInst->getOperand(0).getMBB();
     Cond.push_back(SecondLastInst->getOperand(1));