Rewrite CanShareConstantPoolEntry to be implemented in terms of the

mid-level constant folding APIs instead of doing its own analysis.
This makes it more general (e.g. can now share a <2 x i64> with a
<4 x i32>) and avoid duplicating a bunch of logic.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@149111 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/MachineFunction.cpp

@@ -27,6 +27,7 @@
 #include "llvm/CodeGen/Passes.h"
 #include "llvm/MC/MCAsmInfo.h"
 #include "llvm/MC/MCContext.h"
+#include "llvm/Analysis/ConstantFolding.h"
 #include "llvm/Analysis/DebugInfo.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Target/TargetData.h"
@@ -654,38 +655,37 @@ static bool CanShareConstantPoolEntry(const Constant *A, const Constant *B,
   // reject them.
   if (A->getType() == B->getType()) return false;
 
+  // We can't handle structs or arrays.
+  if (isa<StructType>(A->getType()) || isa<ArrayType>(A->getType()) ||
+      isa<StructType>(B->getType()) || isa<ArrayType>(B->getType()))
+    return false;
+  
   // For now, only support constants with the same size.
   uint64_t StoreSize = TD->getTypeStoreSize(A->getType());
   if (StoreSize != TD->getTypeStoreSize(B->getType()) || 
       StoreSize > 128)
     return false;
 
- 
-  // If a floating-point value and an integer value have the same encoding,
-  // they can share a constant-pool entry.
-  if (const ConstantFP *AFP = dyn_cast<ConstantFP>(A))
-    if (const ConstantInt *BI = dyn_cast<ConstantInt>(B))
-      return AFP->getValueAPF().bitcastToAPInt() == BI->getValue();
-  if (const ConstantFP *BFP = dyn_cast<ConstantFP>(B))
-    if (const ConstantInt *AI = dyn_cast<ConstantInt>(A))
-      return BFP->getValueAPF().bitcastToAPInt() == AI->getValue();
-
-  // Two vectors can share an entry if each pair of corresponding
-  // elements could.
-  if (const ConstantVector *AV = dyn_cast<ConstantVector>(A))
-    if (const ConstantVector *BV = dyn_cast<ConstantVector>(B)) {
-      if (AV->getType()->getNumElements() != BV->getType()->getNumElements())
-        return false;
-      for (unsigned i = 0, e = AV->getType()->getNumElements(); i != e; ++i)
-        if (!CanShareConstantPoolEntry(AV->getOperand(i),
-                                       BV->getOperand(i), TD))
-          return false;
-      return true;
-    }
-
-  // TODO: Handle other cases.
-
-  return false;
+  Type *IntTy = IntegerType::get(A->getContext(), StoreSize*8);
+
+  // Try constant folding a bitcast of both instructions to an integer.  If we
+  // get two identical ConstantInt's, then we are good to share them.  We use
+  // the constant folding APIs to do this so that we get the benefit of
+  // TargetData.
+  if (isa<PointerType>(A->getType()))
+    A = ConstantFoldInstOperands(Instruction::PtrToInt, IntTy,
+                                 const_cast<Constant*>(A), TD);
+  else if (A->getType() != IntTy)
+    A = ConstantFoldInstOperands(Instruction::BitCast, IntTy,
+                                 const_cast<Constant*>(A), TD);
+  if (isa<PointerType>(B->getType()))
+    B = ConstantFoldInstOperands(Instruction::PtrToInt, IntTy,
+                                 const_cast<Constant*>(B), TD);
+  else if (B->getType() != IntTy)
+    B = ConstantFoldInstOperands(Instruction::BitCast, IntTy,
+                                 const_cast<Constant*>(B), TD);
+  
+  return A == B;
 }
 
 /// getConstantPoolIndex - Create a new entry in the constant pool or return