[DAGCombiner][RISCV] Adjust (aext (and (trunc x), cst)) -> (and x, cst) to sext cst based on target preference

[craig.topper]

Summary

RISCV strong prefers i32 values be sign extended to i64. This combine
was always zero extending the constant using APInt methods.

This adjusts the code so that it calls getNode using ISD::ANY_EXTEND instead.
getNode will call TLI.isSExtCheaperThanZExt to decide how to handle
the constant.

Tests were copied from D121598 where I noticed that we were creating
constants that were hard to materialize.

[Luhaocong]

LGTM

[RKSimon]

LGTM

llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

 //===- DAGCombiner.cpp - Implement a DAG node combiner --------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
SDValue DAGCombiner::visitANY_EXTEND(SDNode *N) {
   // Fold (aext (and (trunc x), cst)) -> (and x, cst)
   // if the trunc is not free.
   if (N0.getOpcode() == ISD::AND &&
       N0.getOperand(0).getOpcode() == ISD::TRUNCATE &&
       N0.getOperand(1).getOpcode() == ISD::Constant &&
       !TLI.isTruncateFree(N0.getOperand(0).getOperand(0).getValueType(),
                           N0.getValueType())) {
     SDLoc DL(N);
-    SDValue X = N0.getOperand(0).getOperand(0);
-    X = DAG.getAnyExtOrTrunc(X, DL, VT);
-    APInt Mask = N0.getConstantOperandAPInt(1).zext(VT.getSizeInBits());
-    return DAG.getNode(ISD::AND, DL, VT,
-                       X, DAG.getConstant(Mask, DL, VT));
+    SDValue X = DAG.getAnyExtOrTrunc(N0.getOperand(0).getOperand(0), DL, VT);
+    SDValue Y = DAG.getNode(ISD::ANY_EXTEND, DL, VT, N0.getOperand(1));
+    assert(isa<ConstantSDNode>(Y) && "Expected constant to be folded!");
+    return DAG.getNode(ISD::AND, DL, VT, X, Y);
   }
 
   // fold (aext (load x)) -> (aext (truncate (extload x)))
   // None of the supported targets knows how to perform load and any_ext
   // on vectors in one instruction, so attempt to fold to zext instead.
   if (VT.isVector()) {
     // Try to simplify (zext (load x)).
     if (SDValue foldedExt =

llvm/test/CodeGen/RISCV/and.ll

 ; RV64I:       # %bb.0:
 ; RV64I-NEXT:    slli a0, a0, 52
 ; RV64I-NEXT:    srli a0, a0, 52
 ; RV64I-NEXT:    ret
   %a = and i64 %x, 4095
   ret i64 %a
 }
 
+define i32 @and32_0xfffff000(i32 %x) {
+; RV32I-LABEL: and32_0xfffff000:
+; RV32I:       # %bb.0:
+; RV32I-NEXT:    lui a1, 1048575
+; RV32I-NEXT:    and a0, a0, a1
+; RV32I-NEXT:    ret
+;
+; RV64I-LABEL: and32_0xfffff000:
+; RV64I:       # %bb.0:
+; RV64I-NEXT:    lui a1, 1048575
+; RV64I-NEXT:    and a0, a0, a1
+; RV64I-NEXT:    ret
+  %a = and i32 %x, -4096
+  ret i32 %a
+}
+
+define i32 @and32_0xfffffa00(i32 %x) {
+; RV32I-LABEL: and32_0xfffffa00:
+; RV32I:       # %bb.0:
+; RV32I-NEXT:    andi a0, a0, -1536
+; RV32I-NEXT:    ret
+;
+; RV64I-LABEL: and32_0xfffffa00:
+; RV64I:       # %bb.0:
+; RV64I-NEXT:    andi a0, a0, -1536
+; RV64I-NEXT:    ret
+  %a = and i32 %x, -1536
+  ret i32 %a
+}