[SelectionDAG][X86] Add SelectionDAG::getSignedConstant and use it in a few places. (#104555)

PR #80309 proposes to have users of APInt's uint64_t
constructor opt-in to implicit truncation. Currently, that patch
requires SelectionDAG::getConstant to opt-in.

This patch adds getSignedConstant so we can start fixing some of the
cases that require implicit truncation.

1 files changed, 9 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 7bf90ce..2401bb5 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -1747,6 +1747,15 @@ SDValue SelectionDAG::getConstant(const ConstantInt &Val, const SDLoc &DL,
   return Result;
 }
 
+SDValue SelectionDAG::getSignedConstant(int64_t Val, const SDLoc &DL, EVT VT,
+                                        bool isT, bool isO) {
+  unsigned Size = VT.getScalarSizeInBits();
+  assert(
+      isIntN(Size, Val) &&
+      "getSignedConstant with a int64_t value that doesn't fit in the type!");
+  return getConstant(APInt(Size, Val, true), DL, VT, isT, isO);
+}
+
 SDValue SelectionDAG::getAllOnesConstant(const SDLoc &DL, EVT VT, bool IsTarget,
                                          bool IsOpaque) {
   return getConstant(APInt::getAllOnes(VT.getScalarSizeInBits()), DL, VT,