Fix pr6543: svn r88806 changed MachineJumpTableInfo::getJumpTableIndex() to

always create a new jump table.  The intention was to avoid merging jump
tables in SelectionDAGBuilder, and to wait for the branch folding pass to
merge tables.  Unfortunately, the same getJumpTableIndex() method is also
used to merge tables in branch folding, so as a result of this change
branch tables are never merged.  Worse, the branch folding code is expecting
getJumpTableIndex to always return the index of an existing table, but with
this change, it never does so.  In at least some cases, e.g., pr6543, this
creates references to non-existent tables.

I've fixed the problem by adding a new createJumpTableIndex function, which
will always create a new table, and I've changed getJumpTableIndex to only
look at existing tables.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@98845 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/CodeGen/MachineJumpTableInfo.h b/include/llvm/CodeGen/MachineJumpTableInfo.h
index b8d04bf2132e7a03ad18c26274ac38229ad80d84..85d38ba01c584ed3a592cf5272d4c3dbd85e8a45 100644 (file)
--- a/include/llvm/CodeGen/MachineJumpTableInfo.h
+++ b/include/llvm/CodeGen/MachineJumpTableInfo.h
@@ -83,7 +83,11 @@ public:
   /// getEntryAlignment - Return the alignment of each entry in the jump table.
   unsigned getEntryAlignment(const TargetData &TD) const;
   
-  /// getJumpTableIndex - Create a new jump table or return an existing one.
+  /// createJumpTableIndex - Create a new jump table.
+  ///
+  unsigned createJumpTableIndex(const std::vector<MachineBasicBlock*> &DestBBs);
+  
+  /// getJumpTableIndex - Return the index for an existing jump table.
   ///
   unsigned getJumpTableIndex(const std::vector<MachineBasicBlock*> &DestBBs);
   

diff --git a/lib/CodeGen/MachineFunction.cpp b/lib/CodeGen/MachineFunction.cpp
index 37f3d22630d4d7e3530570c34c4a12eb8da33b67..254b5e7c7be8bfcc4f48c52a7503146262b5ff21 100644 (file)
--- a/lib/CodeGen/MachineFunction.cpp
+++ b/lib/CodeGen/MachineFunction.cpp
@@ -600,16 +600,25 @@ unsigned MachineJumpTableInfo::getEntryAlignment(const TargetData &TD) const {
   return ~0;
 }
 
-/// getJumpTableIndex - Create a new jump table entry in the jump table info
-/// or return an existing one.
+/// createJumpTableIndex - Create a new jump table entry in the jump table info.
 ///
-unsigned MachineJumpTableInfo::getJumpTableIndex(
+unsigned MachineJumpTableInfo::createJumpTableIndex(
                                const std::vector<MachineBasicBlock*> &DestBBs) {
   assert(!DestBBs.empty() && "Cannot create an empty jump table!");
   JumpTables.push_back(MachineJumpTableEntry(DestBBs));
   return JumpTables.size()-1;
 }
 
+/// getJumpTableIndex - Return the index for an existing jump table entry in
+/// the jump table info.
+unsigned MachineJumpTableInfo::getJumpTableIndex(
+                               const std::vector<MachineBasicBlock*> &DestBBs) {
+  for (unsigned i = 0, e = JumpTables.size(); i != e; ++i)
+    if (JumpTables[i].MBBs == DestBBs)
+      return i;
+  assert(false && "getJumpTableIndex failed to find matching table");
+  return ~0;
+}
 
 /// ReplaceMBBInJumpTables - If Old is the target of any jump tables, update
 /// the jump tables to branch to New instead.

diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 4c2cd72d213cf77cdba8e4bf2dc13594c96bb2d8..12096b9a68bb832b70f482ff89b87aff2e1f12e3 100644 (file)
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -1675,11 +1675,10 @@ bool SelectionDAGBuilder::handleJTSwitchCase(CaseRec& CR,
     }
   }
 
-  // Create a jump table index for this jump table, or return an existing
-  // one.
+  // Create a jump table index for this jump table.
   unsigned JTEncoding = TLI.getJumpTableEncoding();
   unsigned JTI = CurMF->getOrCreateJumpTableInfo(JTEncoding)
-                       ->getJumpTableIndex(DestBBs);
+                       ->createJumpTableIndex(DestBBs);
 
   // Set the jump table information so that we can codegen it as a second
   // MachineBasicBlock