[KnownBits] Add implementations for saturating add/sub functions

These where previously missing. Even in the case where overflow is
indeterminate we can still deduce some of the low/high bits.

Reviewed By: RKSimon

Differential Revision: https://reviews.llvm.org/D150102

1 files changed, 32 insertions, 1 deletions

diff --git a/llvm/unittests/Support/KnownBitsTest.cpp b/llvm/unittests/Support/KnownBitsTest.cpp
index 14c5825..457b7c8 100644
--- a/llvm/unittests/Support/KnownBitsTest.cpp
+++ b/llvm/unittests/Support/KnownBitsTest.cpp
@@ -300,7 +300,38 @@ TEST(KnownBitsTest, BinaryExhaustive) {
         return N1.srem(N2);
       },
       checkCorrectnessOnlyBinary);
-
+  testBinaryOpExhaustive(
+      [](const KnownBits &Known1, const KnownBits &Known2) {
+        return KnownBits::sadd_sat(Known1, Known2);
+      },
+      [](const APInt &N1, const APInt &N2) -> std::optional<APInt> {
+        return N1.sadd_sat(N2);
+      },
+      checkCorrectnessOnlyBinary);
+  testBinaryOpExhaustive(
+      [](const KnownBits &Known1, const KnownBits &Known2) {
+        return KnownBits::uadd_sat(Known1, Known2);
+      },
+      [](const APInt &N1, const APInt &N2) -> std::optional<APInt> {
+        return N1.uadd_sat(N2);
+      },
+      checkCorrectnessOnlyBinary);
+  testBinaryOpExhaustive(
+      [](const KnownBits &Known1, const KnownBits &Known2) {
+        return KnownBits::ssub_sat(Known1, Known2);
+      },
+      [](const APInt &N1, const APInt &N2) -> std::optional<APInt> {
+        return N1.ssub_sat(N2);
+      },
+      checkCorrectnessOnlyBinary);
+  testBinaryOpExhaustive(
+      [](const KnownBits &Known1, const KnownBits &Known2) {
+        return KnownBits::usub_sat(Known1, Known2);
+      },
+      [](const APInt &N1, const APInt &N2) -> std::optional<APInt> {
+        return N1.usub_sat(N2);
+      },
+      checkCorrectnessOnlyBinary);
   testBinaryOpExhaustive(
       [](const KnownBits &Known1, const KnownBits &Known2) {
         return KnownBits::shl(Known1, Known2);