Major fix: extract ConstantExpr nodes and decompose them into symbolic

instructions so that (a) constant folding is done automatically before
code generation, and (b) selection does not have to deal with them.
Also, check for ConstantPointerRefs in additional to GlobalValues
when creating a GEP to load a global address.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@4126 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/SparcV9/SparcV9PreSelection.cpp

@@ -23,8 +23,8 @@
 #include "llvm/Annotation.h"
 #include "Support/CommandLine.h"
 #include "Support/NonCopyable.h"
-using std::map;
+#include <algorithm>
-using std::cerr;
+using namespace std;
 
 namespace {
   //===--------------------------------------------------------------------===//
@@ -51,7 +51,7 @@ namespace {
   // The pool of constants that must be emitted for a module.
   // This is a single pool for the entire module and is shared by
   // all invocations of the PreSelection pass for this module by putting
-  // this as as annotation on the Module object.
+  // this as an annotation on the Module object.
   // A single GlobalVariable is created for each constant in the pool
   // representing the memory for that constant.  
   // 
@@ -118,8 +118,6 @@ namespace {
     const TargetMachine &target;
     Function* function;
 
-    GetElementPtrInst* getGlobalAddr(Value* ptr, Instruction* insertBefore = 0);
-
     GlobalVariable* getGlobalForConstant(Constant* CV) {
       Module* M = function->getParent();
       return ConstantPoolForModule::get(M).getGlobalForConstant(CV);
@@ -162,18 +160,76 @@ static RegisterOpt<PreSelection> X("preselect",
                                    "Specialize LLVM code for a target machine",
                                    createPreSelectionPass);
 
-// PreSelection::getGlobalAddr: Put address of a global into a v. register.
+//------------------------------------------------------------------------------
-GetElementPtrInst* 
+// Helper functions used by methods of class PreSelection
-PreSelection::getGlobalAddr(Value* ptr, Instruction* insertBefore)
+//------------------------------------------------------------------------------
+
+
+// getGlobalAddr(): Put address of a global into a v. register.
+static GetElementPtrInst* getGlobalAddr(Value* ptr, Instruction& insertBefore)
 {
+  if (isa<ConstantPointerRef>(ptr))
+    ptr = cast<ConstantPointerRef>(ptr)->getValue();
+
   return (isa<GlobalValue>(ptr))
     ? new GetElementPtrInst(ptr,
                     std::vector<Value*>(1, ConstantSInt::get(Type::LongTy, 0U)),
-                    "addrOfGlobal", insertBefore)
+                    "addrOfGlobal", &insertBefore)
     : NULL;
 }
 
 
+// Wrapper on Constant::classof to use in find_if :-(
+inline static bool nonConstant(const Use& U)
+{
+  return ! isa<Constant>(U);
+}
+
+
+static Instruction* DecomposeConstantExpr(ConstantExpr* CE,
+                                          Instruction& insertBefore)
+{
+  Value *getArg1, *getArg2;
+
+  switch(CE->getOpcode())
+    {
+    case Instruction::Cast:
+      getArg1 = CE->getOperand(0);
+      if (ConstantExpr* CEarg = dyn_cast<ConstantExpr>(getArg1))
+        getArg1 = DecomposeConstantExpr(CEarg, insertBefore);
+      return new CastInst(getArg1, CE->getType(), "constantCast",&insertBefore);
+
+    case Instruction::GetElementPtr:
+#     ifndef NDEBUG
+      assert(find_if(++CE->op_begin(), CE->op_end(),nonConstant) == CE->op_end()
+             && "All indices in ConstantExpr getelementptr must be constant!");
+#     endif
+      getArg1 = CE->getOperand(0);
+      if (ConstantExpr* CEarg = dyn_cast<ConstantExpr>(getArg1))
+        getArg1 = DecomposeConstantExpr(CEarg, insertBefore);
+      else if (GetElementPtrInst* gep = getGlobalAddr(getArg1, insertBefore))
+        getArg1 = gep;
+      return new GetElementPtrInst(getArg1,
+                          std::vector<Value*>(++CE->op_begin(), CE->op_end()),
+                          "constantGEP", &insertBefore);
+
+    default:                            // must be a binary operator
+      assert(CE->getOpcode() >= Instruction::FirstBinaryOp &&
+             CE->getOpcode() <  Instruction::NumBinaryOps &&
+             "Unrecognized opcode in ConstantExpr");
+      getArg1 = CE->getOperand(0);
+      if (ConstantExpr* CEarg = dyn_cast<ConstantExpr>(getArg1))
+        getArg1 = DecomposeConstantExpr(CEarg, insertBefore);
+      getArg2 = CE->getOperand(1);
+      if (ConstantExpr* CEarg = dyn_cast<ConstantExpr>(getArg2))
+        getArg2 = DecomposeConstantExpr(CEarg, insertBefore);
+      return BinaryOperator::create((Instruction::BinaryOps) CE->getOpcode(),
+                                    getArg1, getArg2,
+                                    "constantBinaryOp", &insertBefore);
+    }
+}
+
+
 //------------------------------------------------------------------------------
 // Instruction visitor methods to perform instruction-specific operations
 //------------------------------------------------------------------------------
@@ -192,7 +248,7 @@ void
 PreSelection::visitGetElementPtrInst(GetElementPtrInst &I)
 { 
   // Check for a global and put its address into a register before this instr
-  if (GetElementPtrInst* gep = getGlobalAddr(I.getPointerOperand(), &I))
+  if (GetElementPtrInst* gep = getGlobalAddr(I.getPointerOperand(), I))
     I.setOperand(I.getPointerOperandIndex(), gep); // replace pointer operand
 
   // Decompose multidimensional array references
@@ -208,7 +264,7 @@ void
 PreSelection::visitLoadInst(LoadInst &I)
 { 
   // Check for a global and put its address into a register before this instr
-  if (GetElementPtrInst* gep = getGlobalAddr(I.getPointerOperand(), &I))
+  if (GetElementPtrInst* gep = getGlobalAddr(I.getPointerOperand(), I))
     I.setOperand(I.getPointerOperandIndex(), gep); // replace pointer operand
 
   // Perform other transformations common to all instructions
@@ -221,7 +277,7 @@ void
 PreSelection::visitStoreInst(StoreInst &I)
 { 
   // Check for a global and put its address into a register before this instr
-  if (GetElementPtrInst* gep = getGlobalAddr(I.getPointerOperand(), &I))
+  if (GetElementPtrInst* gep = getGlobalAddr(I.getPointerOperand(), I))
     I.setOperand(I.getPointerOperandIndex(), gep); // replace pointer operand
 
   // Perform other transformations common to all instructions
@@ -229,12 +285,14 @@ PreSelection::visitStoreInst(StoreInst &I)
 }
 
 
-// Cast instructions: make multi-step casts explicit
+// Cast instructions:
-// -- float/double to uint32_t:
+// -- check if argument is a global
-//    If target does not have a float-to-unsigned instruction, we
+// -- make multi-step casts explicit:
-//    need to convert to uint64_t and then to uint32_t, or we may
+//    -- float/double to uint32_t:
-//    overflow the signed int representation for legal uint32_t
+//         If target does not have a float-to-unsigned instruction, we
-//    values.  Expand this without checking target.
+//         need to convert to uint64_t and then to uint32_t, or we may
+//         overflow the signed int representation for legal uint32_t
+//         values.  Expand this without checking target.
 // 
 void
 PreSelection::visitCastInst(CastInst &I)
@@ -242,8 +300,12 @@ PreSelection::visitCastInst(CastInst &I)
   CastInst* castI = NULL;
 
   // Check for a global and put its address into a register before this instr
-  if (I.getType() == Type::UIntTy &&
+  if (GetElementPtrInst* gep = getGlobalAddr(I.getOperand(0), I))
-      I.getOperand(0)->getType()->isFloatingPoint())
+    {
+      I.setOperand(0, gep);             // replace pointer operand
+    }
+  else if (I.getType() == Type::UIntTy &&
+           I.getOperand(0)->getType()->isFloatingPoint())
     { // insert a cast-fp-to-long before I, and then replace the operand of I
       castI = new CastInst(I.getOperand(0), Type::LongTy, "fp2Long2Uint", &I);
       I.setOperand(0, castI);           // replace fp operand with long
@@ -287,10 +349,15 @@ void
 PreSelection::visitOneOperand(Instruction &I, Constant* CV, unsigned opNum,
                               Instruction& insertBefore)
 {
-  if (target.getInstrInfo().ConstantTypeMustBeLoaded(CV))
+  if (ConstantExpr* CE = dyn_cast<ConstantExpr>(CV))
+    { // load-time constant: factor it out so we optimize as best we can
+      Instruction* computeConst = DecomposeConstantExpr(CE, insertBefore);
+      I.setOperand(opNum, computeConst); // replace expr operand with result
+    }
+  else if (target.getInstrInfo().ConstantTypeMustBeLoaded(CV))
     { // load address of constant into a register, then load the constant
       GetElementPtrInst* gep = getGlobalAddr(getGlobalForConstant(CV),
-                                             &insertBefore);
+                                             insertBefore);
       LoadInst* ldI = new LoadInst(gep, "loadConst", &insertBefore);
       I.setOperand(opNum, ldI);        // replace operand with copy in v.reg.
     }
@@ -302,6 +369,7 @@ PreSelection::visitOneOperand(Instruction &I, Constant* CV, unsigned opNum,
     }
 }
 
+
 //===----------------------------------------------------------------------===//
 // createPreSelectionPass - Public entrypoint for pre-selection pass
 // and this file as a whole...