Optimize Thumb2 jumptable to use tbb / tbh when all the offsets fit in byte / halfword.

[oota-llvm.git] / lib / CodeGen / BranchFolding.cpp

diff --git a/lib/CodeGen/BranchFolding.cpp b/lib/CodeGen/BranchFolding.cpp
index 583009c74a3b6375175801a9eab558478ff0f642..193bbb610f792065626009ae1a0d53593c8c3cd6 100644 (file)
--- a/lib/CodeGen/BranchFolding.cpp
+++ b/lib/CodeGen/BranchFolding.cpp
@@ -27,6 +27,7 @@
 #include "llvm/Target/TargetRegisterInfo.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
+#include "llvm/Support/ErrorHandling.h"
 #include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/ADT/STLExtras.h"
@@ -461,7 +462,7 @@ static bool MergeCompare(const std::pair<unsigned,MachineBasicBlock*> &p,
       // _GLIBCXX_DEBUG checks strict weak ordering, which involves comparing
       // an object with itself.
 #ifndef _GLIBCXX_DEBUG
-      assert(0 && "Predecessor appears twice");
+      llvm_unreachable("Predecessor appears twice");
 #endif
       return false;
     }
@@ -1092,6 +1093,21 @@ void BranchFolder::OptimizeBlock(MachineBasicBlock *MBB) {
             } else {
               DidChange = true;
               PMBB->ReplaceUsesOfBlockWith(MBB, CurTBB);
+              // If this change resulted in PMBB ending in a conditional
+              // branch where both conditions go to the same destination,
+              // change this to an unconditional branch (and fix the CFG).
+              MachineBasicBlock *NewCurTBB = 0, *NewCurFBB = 0;
+              SmallVector<MachineOperand, 4> NewCurCond;
+              bool NewCurUnAnalyzable = TII->AnalyzeBranch(*PMBB, NewCurTBB,
+                      NewCurFBB, NewCurCond, true);
+              if (!NewCurUnAnalyzable && NewCurTBB && NewCurTBB == NewCurFBB) {
+                TII->RemoveBranch(*PMBB);
+                NewCurCond.clear(); 
+                TII->InsertBranch(*PMBB, NewCurTBB, 0, NewCurCond);
+                MadeChange = true;
+                ++NumBranchOpts;
+                PMBB->CorrectExtraCFGEdges(NewCurTBB, NewCurFBB, false);
+              }
             }
           }