[KnownBits] Handle shifts over wide types

Do not assert if the bit width is larger than 64 bits. This case
is currently hidden from the IR layer by other checks, but gets
exposed with future changes.

diff --git a/llvm/lib/Support/KnownBits.cpp b/llvm/lib/Support/KnownBits.cpp
index 0fd3e5a..ddeb6a4 100644 (file)
--- a/llvm/lib/Support/KnownBits.cpp
+++ b/llvm/lib/Support/KnownBits.cpp
@@ -195,8 +195,8 @@ KnownBits KnownBits::shl(const KnownBits &LHS, const KnownBits &RHS) {
   // possible shifts.
   APInt MaxShiftAmount = RHS.getMaxValue();
   if (!LHS.isUnknown()) {
-    uint64_t ShiftAmtZeroMask = (~RHS.Zero).getZExtValue();
-    uint64_t ShiftAmtOneMask = RHS.One.getZExtValue();
+    uint64_t ShiftAmtZeroMask = (~RHS.Zero).zextOrTrunc(64).getZExtValue();
+    uint64_t ShiftAmtOneMask = RHS.One.zextOrTrunc(64).getZExtValue();
     assert(MinShiftAmount.ult(MaxShiftAmount) && "Illegal shift range");
     Known.Zero.setAllBits();
     Known.One.setAllBits();
@@ -251,8 +251,8 @@ KnownBits KnownBits::lshr(const KnownBits &LHS, const KnownBits &RHS) {
   // possible shifts.
   APInt MaxShiftAmount = RHS.getMaxValue();
   if (!LHS.isUnknown()) {
-    uint64_t ShiftAmtZeroMask = (~RHS.Zero).getZExtValue();
-    uint64_t ShiftAmtOneMask = RHS.One.getZExtValue();
+    uint64_t ShiftAmtZeroMask = (~RHS.Zero).zextOrTrunc(64).getZExtValue();
+    uint64_t ShiftAmtOneMask = RHS.One.zextOrTrunc(64).getZExtValue();
     assert(MinShiftAmount.ult(MaxShiftAmount) && "Illegal shift range");
     Known.Zero.setAllBits();
     Known.One.setAllBits();
@@ -312,8 +312,8 @@ KnownBits KnownBits::ashr(const KnownBits &LHS, const KnownBits &RHS) {
   // possible shifts.
   APInt MaxShiftAmount = RHS.getMaxValue();
   if (!LHS.isUnknown()) {
-    uint64_t ShiftAmtZeroMask = (~RHS.Zero).getZExtValue();
-    uint64_t ShiftAmtOneMask = RHS.One.getZExtValue();
+    uint64_t ShiftAmtZeroMask = (~RHS.Zero).zextOrTrunc(64).getZExtValue();
+    uint64_t ShiftAmtOneMask = RHS.One.zextOrTrunc(64).getZExtValue();
     assert(MinShiftAmount.ult(MaxShiftAmount) && "Illegal shift range");
     Known.Zero.setAllBits();
     Known.One.setAllBits();

diff --git a/llvm/unittests/Support/KnownBitsTest.cpp b/llvm/unittests/Support/KnownBitsTest.cpp
index 28f904e..ece7e80 100644 (file)
--- a/llvm/unittests/Support/KnownBitsTest.cpp
+++ b/llvm/unittests/Support/KnownBitsTest.cpp
@@ -352,6 +352,20 @@ TEST(KnownBitsTest, UnaryExhaustive) {
       [](const APInt &N) { return N * N; }, checkCorrectnessOnlyUnary);
 }
 
+TEST(KnownBitsTest, WideShifts) {
+  unsigned BitWidth = 128;
+  KnownBits Unknown(BitWidth);
+  KnownBits AllOnes = KnownBits::makeConstant(APInt::getAllOnes(BitWidth));
+
+  KnownBits ShlResult(BitWidth);
+  ShlResult.makeNegative();
+  EXPECT_EQ(KnownBits::shl(AllOnes, Unknown), ShlResult);
+  KnownBits LShrResult(BitWidth);
+  LShrResult.One.setBit(0);
+  EXPECT_EQ(KnownBits::lshr(AllOnes, Unknown), LShrResult);
+  EXPECT_EQ(KnownBits::ashr(AllOnes, Unknown), AllOnes);
+}
+
 TEST(KnownBitsTest, ICmpExhaustive) {
   unsigned Bits = 4;
   ForeachKnownBits(Bits, [&](const KnownBits &Known1) {