[APInt] Add saturating left-shift ops

Summary:
There are `*_ov()` functions already, so at least for consistency it may be good to also have saturating variants.
These may or may not be needed for `ConstantRange`'s `shlWithNoWrap()`

Reviewers: spatel, nikic

Reviewed By: nikic

Subscribers: hiraditya, dexonsmith, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D69398

1 files changed, 19 insertions, 0 deletions

diff --git a/llvm/lib/Support/APInt.cpp b/llvm/lib/Support/APInt.cpp
index df2e6197b2a..08e9757702a 100644
--- a/llvm/lib/Support/APInt.cpp
+++ b/llvm/lib/Support/APInt.cpp
@@ -2070,6 +2070,25 @@ APInt APInt::umul_sat(const APInt &RHS) const {
   return APInt::getMaxValue(BitWidth);
 }
 
+APInt APInt::sshl_sat(const APInt &RHS) const {
+  bool Overflow;
+  APInt Res = sshl_ov(RHS, Overflow);
+  if (!Overflow)
+    return Res;
+
+  return isNegative() ? APInt::getSignedMinValue(BitWidth)
+                      : APInt::getSignedMaxValue(BitWidth);
+}
+
+APInt APInt::ushl_sat(const APInt &RHS) const {
+  bool Overflow;
+  APInt Res = ushl_ov(RHS, Overflow);
+  if (!Overflow)
+    return Res;
+
+  return APInt::getMaxValue(BitWidth);
+}
+
 void APInt::fromString(unsigned numbits, StringRef str, uint8_t radix) {
   // Check our assumptions here
   assert(!str.empty() && "Invalid string length");