[ConstantRange] Add ushl_sat()/sshl_sat() methods.

Summary:
To be used in `ConstantRange::shlWithNoOverflow()`,
may in future be useful for when saturating shift/mul ops are added.

Unlike `ConstantRange::shl()`, these are precise.

Reviewers: nikic, spatel, reames

Reviewed By: nikic

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D69960

include/llvm/IR/ConstantRange.h

@@ -434,6 +434,14 @@ public:
   /// Perform a signed saturating subtraction of two constant ranges.
   ConstantRange ssub_sat(const ConstantRange &Other) const;
 
+  /// Perform an unsigned saturating left shift of this constant range by a
+  /// value in \p Other.
+  ConstantRange ushl_sat(const ConstantRange &Other) const;
+
+  /// Perform a signed saturating left shift of this constant range by a
+  /// value in \p Other.
+  ConstantRange sshl_sat(const ConstantRange &Other) const;
+
   /// Return a new range that is the logical not of the current set.
   ConstantRange inverse() const;
 

lib/IR/ConstantRange.cpp

@@ -1333,6 +1333,26 @@ ConstantRange ConstantRange::ssub_sat(const ConstantRange &Other) const {
   return getNonEmpty(std::move(NewL), std::move(NewU));
 }
 
+ConstantRange ConstantRange::ushl_sat(const ConstantRange &Other) const {
+  if (isEmptySet() || Other.isEmptySet())
+    return getEmpty();
+
+  APInt NewL = getUnsignedMin().ushl_sat(Other.getUnsignedMin());
+  APInt NewU = getUnsignedMax().ushl_sat(Other.getUnsignedMax()) + 1;
+  return getNonEmpty(std::move(NewL), std::move(NewU));
+}
+
+ConstantRange ConstantRange::sshl_sat(const ConstantRange &Other) const {
+  if (isEmptySet() || Other.isEmptySet())
+    return getEmpty();
+
+  APInt Min = getSignedMin(), Max = getSignedMax();
+  APInt ShAmtMin = Other.getUnsignedMin(), ShAmtMax = Other.getUnsignedMax();
+  APInt NewL = Min.sshl_sat(isAllNonNegative() ? ShAmtMin : ShAmtMax);
+  APInt NewU = Max.sshl_sat(isAllNegative() ? ShAmtMin : ShAmtMax) + 1;
+  return getNonEmpty(std::move(NewL), std::move(NewU));
+}
+
 ConstantRange ConstantRange::inverse() const {
   if (isFullSet())
     return getEmpty();

unittests/IR/ConstantRangeTest.cpp

@@ -2217,6 +2217,14 @@ TEST_F(ConstantRangeTest, USubSat) {
       });
 }
 
+TEST_F(ConstantRangeTest, UShlSat) {
+  TestUnsignedBinOpExhaustive(
+      [](const ConstantRange &CR1, const ConstantRange &CR2) {
+        return CR1.ushl_sat(CR2);
+      },
+      [](const APInt &N1, const APInt &N2) { return N1.ushl_sat(N2); });
+}
+
 TEST_F(ConstantRangeTest, SAddSat) {
   TestSignedBinOpExhaustive(
       [](const ConstantRange &CR1, const ConstantRange &CR2) {
@@ -2237,6 +2245,14 @@ TEST_F(ConstantRangeTest, SSubSat) {
       });
 }
 
+TEST_F(ConstantRangeTest, SShlSat) {
+  TestSignedBinOpExhaustive(
+      [](const ConstantRange &CR1, const ConstantRange &CR2) {
+        return CR1.sshl_sat(CR2);
+      },
+      [](const APInt &N1, const APInt &N2) { return N1.sshl_sat(N2); });
+}
+
 TEST_F(ConstantRangeTest, Abs) {
   unsigned Bits = 4;
   EnumerateConstantRanges(Bits, [&](const ConstantRange &CR) {