[clang] [CIR] Fold constant add and sub operations (PR #218398)

[via cfe-commits]

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@@ -3185,6 +3185,71 @@ OpFoldResult cir::NotOp::fold(FoldAdaptor adaptor) {
   return {};
 }
 
+//===----------------------------------------------------------------------===//
+// AddOp & SubOp
+//===----------------------------------------------------------------------===//
+
+// Constant-fold integer add/sub. Honors nsw/nuw by folding to poison on the
+// corresponding overflow, and folds saturated arithmetic by clamping.
+static OpFoldResult foldAddSubConst(mlir::Type ty, const APInt &lhs,
+                                    const APInt &rhs, bool isSub, bool nsw,
+                                    bool nuw, bool sat) {
+  bool isSigned = mlir::cast<cir::IntType>(ty).isSigned();
+  if (sat) {
+    APInt res = isSub ? (isSigned ? lhs.ssub_sat(rhs) : lhs.usub_sat(rhs))
+                      : (isSigned ? lhs.sadd_sat(rhs) : lhs.uadd_sat(rhs));
+    return cir::IntAttr::get(ty, res);
+  }
+
+  bool poison = false;
+  if (nsw) {
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prometheusfma-llvm wrote:

Thanks for taking a look. What about fixups added in the recent commit? Does that look fine?

https://github.com/llvm/llvm-project/pull/218398