Add a flag to disable jump table generation (all

switches use the binary search algorithm) for
environments that don't support it.  PPC64 JIT
is such an environment; turn the flag on for that.

llvm-svn: 54248

include/llvm/Target/TargetOptions.h

@@ -97,6 +97,10 @@ namespace llvm {
   /// VerboseAsm - When this flag is set, the asm printer prints additional
   /// comments to asm directives.
   extern bool VerboseAsm;
+
+  /// DisableJumpTables - This flag indicates jump tables should not be 
+  /// generated.
+  extern bool DisableJumpTables;
 } // End llvm namespace
 
 #endif

lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp

@@ -1916,7 +1916,8 @@ bool SelectionDAGLowering::handleSmallSwitchRange(CaseRec& CR,
 }
 
 static inline bool areJTsAllowed(const TargetLowering &TLI) {
-  return (TLI.isOperationLegal(ISD::BR_JT, MVT::Other) ||
+  return !DisableJumpTables &&
+          (TLI.isOperationLegal(ISD::BR_JT, MVT::Other) ||
            TLI.isOperationLegal(ISD::BRIND, MVT::Other));
 }
   

lib/Target/PowerPC/PPCTargetMachine.cpp

@@ -17,6 +17,7 @@
 #include "llvm/Module.h"
 #include "llvm/PassManager.h"
 #include "llvm/Target/TargetMachineRegistry.h"
+#include "llvm/Target/TargetOptions.h"
 using namespace llvm;
 
 // Register the targets
@@ -144,6 +145,9 @@ bool PPCTargetMachine::addCodeEmitter(PassManagerBase &PM, bool Fast,
     // instructions to materialize arbitrary global variable + function +
     // constant pool addresses.
     setRelocationModel(Reloc::PIC_);
+    // Temporary workaround for the inability of PPC64 JIT to handle jump
+    // tables.
+    DisableJumpTables = true;      
   } else {
     setRelocationModel(Reloc::Static);
   }

lib/Target/TargetMachine.cpp

@@ -39,6 +39,7 @@ namespace llvm {
   unsigned StackAlignment;
   bool RealignStack;
   bool VerboseAsm;
+  bool DisableJumpTables;
 }
 
 static cl::opt<bool, true> PrintCode("print-machineinstrs",
@@ -156,6 +157,11 @@ AsmVerbose("asm-verbose", cl::desc("Add comments to directives."),
            cl::location(VerboseAsm),
            cl::init(false));
 
+static cl::opt<bool, true>
+DisableSwitchTables(cl::Hidden, "disable-jump-tables", 
+           cl::desc("Do not generate jump tables."),
+           cl::location(DisableJumpTables),
+           cl::init(false));
 
 //---------------------------------------------------------------------------
 // TargetMachine Class