[InstCombine] canonicalize funnel shift constant shift amount to be modulo bitwidth

The shift argument is defined to be modulo the bitwidth, so if that argument
is a constant, we can always reduce the constant to its minimal form to allow
better CSE and other follow-on transforms.

We need to be careful to ignore constant expressions here, or we will likely
infinite loop. I'm adding a general vector constant query for that case.

Differential Revision: https://reviews.llvm.org/D59374

llvm-svn: 356192

1 files changed, 10 insertions, 0 deletions

diff --git a/llvm/lib/IR/Constants.cpp b/llvm/lib/IR/Constants.cpp
index 00d6cc7..a161992 100644
--- a/llvm/lib/IR/Constants.cpp
+++ b/llvm/lib/IR/Constants.cpp
@@ -260,6 +260,16 @@ bool Constant::containsUndefElement() const {
   return false;
 }
 
+bool Constant::containsConstantExpression() const {
+  if (!getType()->isVectorTy())
+    return false;
+  for (unsigned i = 0, e = getType()->getVectorNumElements(); i != e; ++i)
+    if (isa<ConstantExpr>(getAggregateElement(i)))
+      return true;
+
+  return false;
+}
+
 /// Constructor to create a '0' constant of arbitrary type.
 Constant *Constant::getNullValue(Type *Ty) {
   switch (Ty->getTypeID()) {