[ADT] Add implementations for avgFloor and avgCeil to APInt (#84431)

Supports both signed and unsigned expansions.

SelectionDAG now calls the APInt implementation of these functions.

Fixes #84211.

1 files changed, 36 insertions, 0 deletions

diff --git a/llvm/lib/Support/APInt.cpp b/llvm/lib/Support/APInt.cpp
index e686b97..7053f3b 100644
--- a/llvm/lib/Support/APInt.cpp
+++ b/llvm/lib/Support/APInt.cpp
@@ -3094,3 +3094,39 @@ void llvm::LoadIntFromMemory(APInt &IntVal, const uint8_t *Src,
     memcpy(Dst + sizeof(uint64_t) - LoadBytes, Src, LoadBytes);
   }
 }
+
+APInt APIntOps::avgFloorS(const APInt &C1, const APInt &C2) {
+  // Return floor((C1 + C2)/2)
+  assert(C1.getBitWidth() == C2.getBitWidth() && "Unequal bitwidths");
+  unsigned FullWidth = C1.getBitWidth() + 1;
+  APInt C1Ext = C1.sext(FullWidth);
+  APInt C2Ext = C2.sext(FullWidth);
+  return (C1Ext + C2Ext).extractBits(C1.getBitWidth(), 1);
+}
+
+APInt APIntOps::avgFloorU(const APInt &C1, const APInt &C2) {
+  // Return floor((C1 + C2)/2)
+  assert(C1.getBitWidth() == C2.getBitWidth() && "Unequal bitwidths");
+  unsigned FullWidth = C1.getBitWidth() + 1;
+  APInt C1Ext = C1.zext(FullWidth);
+  APInt C2Ext = C2.zext(FullWidth);
+  return (C1Ext + C2Ext).extractBits(C1.getBitWidth(), 1);
+}
+
+APInt APIntOps::avgCeilS(const APInt &C1, const APInt &C2) {
+  // Return ceil((C1 + C2)/2)
+  assert(C1.getBitWidth() == C2.getBitWidth() && "Unequal bitwidths");
+  unsigned FullWidth = C1.getBitWidth() + 1;
+  APInt C1Ext = C1.sext(FullWidth);
+  APInt C2Ext = C2.sext(FullWidth);
+  return (C1Ext + C2Ext + 1).extractBits(C1.getBitWidth(), 1);
+}
+
+APInt APIntOps::avgCeilU(const APInt &C1, const APInt &C2) {
+  // Return ceil((C1 + C2)/2)
+  assert(C1.getBitWidth() == C2.getBitWidth() && "Unequal bitwidths");
+  unsigned FullWidth = C1.getBitWidth() + 1;
+  APInt C1Ext = C1.zext(FullWidth);
+  APInt C2Ext = C2.zext(FullWidth);
+  return (C1Ext + C2Ext + 1).extractBits(C1.getBitWidth(), 1);
+}