[RISCV] Use getSignedConstant for negative values. (#125903)

The APInt constructor asserts if bits are set past the size of the APInt
unless it is signed. This currently fails on RV32 because more than XLen
bits are set.

(cherry picked from commit 0d7ee52)

Author: topperc

llvm/lib/Target/RISCV/RISCVISelLowering.cpp

@@ -16297,7 +16297,7 @@ static SDValue performVP_REVERSECombine(SDNode *N, SelectionDAG &DAG,
   SDValue Temp2 = DAG.getNode(ISD::MUL, DL, XLenVT, Temp1,
                               DAG.getConstant(ElemWidthByte, DL, XLenVT));
   SDValue Base = DAG.getNode(ISD::ADD, DL, XLenVT, VPLoad->getBasePtr(), Temp2);
-  SDValue Stride = DAG.getConstant(-ElemWidthByte, DL, XLenVT);
+  SDValue Stride = DAG.getSignedConstant(-ElemWidthByte, DL, XLenVT);
 
   MachineFunction &MF = DAG.getMachineFunction();
   MachinePointerInfo PtrInfo(VPLoad->getAddressSpace());
@@ -16358,7 +16358,7 @@ static SDValue performVP_STORECombine(SDNode *N, SelectionDAG &DAG,
                               DAG.getConstant(ElemWidthByte, DL, XLenVT));
   SDValue Base =
       DAG.getNode(ISD::ADD, DL, XLenVT, VPStore->getBasePtr(), Temp2);
-  SDValue Stride = DAG.getConstant(-ElemWidthByte, DL, XLenVT);
+  SDValue Stride = DAG.getSignedConstant(-ElemWidthByte, DL, XLenVT);
 
   MachineFunction &MF = DAG.getMachineFunction();
   MachinePointerInfo PtrInfo(VPStore->getAddressSpace());

llvm/test/CodeGen/RISCV/rvv/vp-combine-reverse-load.ll

@@ -1,4 +1,5 @@
 ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -mtriple=riscv32 -mattr=+f,+v -verify-machineinstrs < %s | FileCheck %s
 ; RUN: llc -mtriple=riscv64 -mattr=+f,+v -verify-machineinstrs < %s | FileCheck %s
 
 define <vscale x 2 x float> @test_reverse_load_combiner(<vscale x 2 x float>* %ptr, i32 zeroext %evl) {

llvm/test/CodeGen/RISCV/rvv/vp-combine-store-reverse.ll

@@ -1,4 +1,5 @@
 ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -mtriple=riscv32 -mattr=+f,+v -verify-machineinstrs < %s | FileCheck %s
 ; RUN: llc -mtriple=riscv64 -mattr=+f,+v -verify-machineinstrs < %s | FileCheck %s
 
 define void @test_store_reverse_combiner(<vscale x 2 x float> %val, <vscale x 2 x float>* %ptr, i32 zeroext %evl) {