[Hexagon] Split large offsets into properly aligned addends

llvm-svn: 341851

1 files changed, 9 insertions, 0 deletions

diff --git a/llvm/lib/Target/Hexagon/HexagonConstExtenders.cpp b/llvm/lib/Target/Hexagon/HexagonConstExtenders.cpp
index 81bb36135d8..efbf6fe9c36 100644
--- a/llvm/lib/Target/Hexagon/HexagonConstExtenders.cpp
+++ b/llvm/lib/Target/Hexagon/HexagonConstExtenders.cpp
@@ -1708,6 +1708,15 @@ bool HCE::replaceInstrExpr(const ExtDesc &ED, const ExtenderInit &ExtI,
 
     // Clamp Diff to the 16 bit range.
     int32_t D = isInt<16>(Diff) ? Diff : (Diff > 0 ? 32767 : -32768);
+    if (Diff > 32767) {
+      // Split Diff into two values: one that is close to min/max int16,
+      // and the other being the rest, and such that both have the same
+      // "alignment" as Diff.
+      uint32_t UD = Diff;
+      OffsetRange R = getOffsetRange(MI.getOperand(0));
+      uint32_t A = std::min<uint32_t>(R.Align, 1u << countTrailingZeros(UD));
+      D &= ~(A-1);
+    }
     BuildMI(MBB, At, dl, HII->get(IdxOpc))
       .add(MI.getOperand(0))
       .add(MachineOperand(ExtR))