}
}
- // FIXME: Maybe combine the next two transforms to handle the no cast case
- // more efficiently. Support vector types. Cleanup code by using m_OneUse.
-
- // Transform trunc(lshr (zext A), Cst) to eliminate one type conversion.
- Value *A = nullptr;
- if (Src->hasOneUse() &&
- match(Src, m_LShr(m_ZExt(m_Value(A)), m_ConstantInt(Cst)))) {
- // We have three types to worry about here, the type of A, the source of
- // the truncate (MidSize), and the destination of the truncate. We know that
- // ASize < MidSize and MidSize > ResultSize, but don't know the relation
- // between ASize and ResultSize.
- unsigned ASize = A->getType()->getPrimitiveSizeInBits();
-
- // If the shift amount is larger than the size of A, then the result is
- // known to be zero because all the input bits got shifted out.
- if (Cst->getZExtValue() >= ASize)
- return replaceInstUsesWith(Trunc, Constant::getNullValue(DestTy));
-
- // Since we're doing an lshr and a zero extend, and know that the shift
- // amount is smaller than ASize, it is always safe to do the shift in A's
- // type, then zero extend or truncate to the result.
- Value *Shift = Builder.CreateLShr(A, Cst->getZExtValue());
- Shift->takeName(Src);
- return CastInst::CreateIntegerCast(Shift, DestTy, false);
- }
-
+ Value *A;
Constant *C;
if (match(Src, m_LShr(m_SExt(m_Value(A)), m_Constant(C)))) {
unsigned AWidth = A->getType()->getScalarSizeInBits();