From d1ec31dca534a8816d7f2fcbfdc7ed4476b471d3 Mon Sep 17 00:00:00 2001
From: Bob Wilson <bob.wilson@apple.com>
Date: Thu, 18 Mar 2010 18:42:41 +0000
Subject: [PATCH] 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
---
 include/llvm/CodeGen/MachineJumpTableInfo.h      |  6 +++++-
 lib/CodeGen/MachineFunction.cpp                  | 15 ++++++++++++---
 lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp |  5 ++---
 3 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/include/llvm/CodeGen/MachineJumpTableInfo.h b/include/llvm/CodeGen/MachineJumpTableInfo.h
index b8d04bf2132..85d38ba01c5 100644
--- 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 37f3d22630d..254b5e7c7be 100644
--- 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 4c2cd72d213..12096b9a68b 100644
--- 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