[RISCV] Apply IsSignExtendingOpW = 1 on fcvtmod.w.d (llvm#69633)

Such that RISCVOptWInstrs can eliminate the redundant sign extend.

Author: mshockwave

llvm/lib/Target/RISCV/RISCVInstrInfoZfa.td

@@ -112,6 +112,7 @@ def FROUND_D : FPUnaryOp_r_frm<0b0100001, 0b00100, FPR64, FPR64, "fround.d">,
 def FROUNDNX_D : FPUnaryOp_r_frm<0b0100001, 0b00101, FPR64, FPR64, "froundnx.d">,
                  Sched<[WriteFRoundF64, ReadFRoundF64]>;
 
+let IsSignExtendingOpW = 1 in
 def FCVTMOD_W_D
     : FPUnaryOp_r_rtz<0b1100001, 0b01000, GPR, FPR64, "fcvtmod.w.d">,
       Sched<[WriteFCvtF64ToI32, ReadFCvtF64ToI32]>;

llvm/test/CodeGen/RISCV/opt-w-instrs.mir

@@ -0,0 +1,30 @@
+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py UTC_ARGS: --version 3
+# RUN: llc -mtriple=riscv64 -mattr='+d,+zfa' -verify-machineinstrs -run-pass=riscv-opt-w-instrs %s -o - | FileCheck %s --check-prefix=CHECK-ZFA
+
+---
+name:            fcvtmod_w_d
+tracksRegLiveness: true
+body:             |
+  bb.0.entry:
+    liveins: $x10, $x11
+
+    ; CHECK-ZFA-LABEL: name: fcvtmod_w_d
+    ; CHECK-ZFA: liveins: $x10, $x11
+    ; CHECK-ZFA-NEXT: {{  $}}
+    ; CHECK-ZFA-NEXT: [[COPY:%[0-9]+]]:fpr64 = COPY $x10
+    ; CHECK-ZFA-NEXT: [[COPY1:%[0-9]+]]:gpr = COPY $x11
+    ; CHECK-ZFA-NEXT: [[FCVTMOD_W_D:%[0-9]+]]:gpr = nofpexcept FCVTMOD_W_D [[COPY]], 1
+    ; CHECK-ZFA-NEXT: [[ADD:%[0-9]+]]:gpr = ADD [[COPY1]], [[FCVTMOD_W_D]]
+    ; CHECK-ZFA-NEXT: $x10 = COPY [[ADD]]
+    ; CHECK-ZFA-NEXT: $x11 = COPY [[FCVTMOD_W_D]]
+    ; CHECK-ZFA-NEXT: PseudoRET
+    %0:fpr64 = COPY $x10
+    %1:gpr = COPY $x11
+
+    %2:gpr = nofpexcept FCVTMOD_W_D %0, 1
+    %3:gpr = ADD %1, %2
+    %4:gpr = ADDIW %2, 0
+    $x10 = COPY %3
+    $x11 = COPY %4
+    PseudoRET
+...