-/// isBytewiseValue - If the specified value can be set by repeating the same
-/// byte in memory, return the i8 value that it is represented with. This is
-/// true for all i8 values obviously, but is also true for i32 0, i32 -1,
-/// i16 0xF0F0, double 0.0 etc. If the value can't be handled with a repeated
-/// byte store (e.g. i16 0x1234), return null.
-static Value *isBytewiseValue(Value *V) {
- // All byte-wide stores are splatable, even of arbitrary variables.
- if (V->getType()->isIntegerTy(8)) return V;
-
- // Constant float and double values can be handled as integer values if the
- // corresponding integer value is "byteable". An important case is 0.0.
- if (ConstantFP *CFP = dyn_cast<ConstantFP>(V)) {
- if (CFP->getType()->isFloatTy())
- V = ConstantExpr::getBitCast(CFP, Type::getInt32Ty(V->getContext()));
- if (CFP->getType()->isDoubleTy())
- V = ConstantExpr::getBitCast(CFP, Type::getInt64Ty(V->getContext()));
- // Don't handle long double formats, which have strange constraints.
- }
-
- // We can handle constant integers that are power of two in size and a
- // multiple of 8 bits.
- if (ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
- unsigned Width = CI->getBitWidth();
- if (isPowerOf2_32(Width) && Width > 8) {
- // We can handle this value if the recursive binary decomposition is the
- // same at all levels.
- APInt Val = CI->getValue();
- APInt Val2;
- while (Val.getBitWidth() != 8) {
- unsigned NextWidth = Val.getBitWidth()/2;
- Val2 = Val.lshr(NextWidth);
- Val2 = Val2.trunc(Val.getBitWidth()/2);
- Val = Val.trunc(Val.getBitWidth()/2);
-
- // If the top/bottom halves aren't the same, reject it.
- if (Val != Val2)
- return 0;
- }
- return ConstantInt::get(V->getContext(), Val);
- }
- }
-
- // A ConstantArray is splatable if all its members are equal and also
- // splatable.
- if (ConstantArray *CA = dyn_cast<ConstantArray>(V)) {
- if (CA->getNumOperands() == 0)
- return 0;
-
- Value *Val = isBytewiseValue(CA->getOperand(0));
- if (!Val)
- return 0;
-
- for (unsigned I = 1, E = CA->getNumOperands(); I != E; ++I)
- if (CA->getOperand(I-1) != CA->getOperand(I))
- return 0;
-
- return Val;
- }
-
- // Conceptually, we could handle things like:
- // %a = zext i8 %X to i16
- // %b = shl i16 %a, 8
- // %c = or i16 %a, %b
- // but until there is an example that actually needs this, it doesn't seem
- // worth worrying about.
- return 0;
-}
-