[RISCV] Add CZERO_EQZ/CZERO_NEZ to ComputeNumSignBitsForTargetNode.

[wangpc]

LGTM

llvm/lib/Target/RISCV/RISCVISelLowering.cpp

unsigned RISCVTargetLowering::ComputeNumSignBitsForTargetNode(
   case RISCVISD::SELECT_CC: {
     unsigned Tmp =
         DAG.ComputeNumSignBits(Op.getOperand(3), DemandedElts, Depth + 1);
     if (Tmp == 1) return 1;  // Early out.
     unsigned Tmp2 =
         DAG.ComputeNumSignBits(Op.getOperand(4), DemandedElts, Depth + 1);
     return std::min(Tmp, Tmp2);
   }
+  case RISCVISD::CZERO_EQZ:
+  case RISCVISD::CZERO_NEZ:
+    // Output is either all zero or operand 0. We can propagate sign bit count
+    // from operand 0.
+    return DAG.ComputeNumSignBits(Op.getOperand(0), DemandedElts, Depth + 1);
   case RISCVISD::ABSW: {
     // We expand this at isel to negw+max. The result will have 33 sign bits
     // if the input has at least 33 sign bits.
     unsigned Tmp =
         DAG.ComputeNumSignBits(Op.getOperand(0), DemandedElts, Depth + 1);
     if (Tmp < 33) return 1;
     return 33;
   }

llvm/test/CodeGen/RISCV/condops.ll

 ; RV64I-NEXT:    ret
 ;
 ; RV64XVENTANACONDOPS-LABEL: numsignbits:
 ; RV64XVENTANACONDOPS:       # %bb.0:
 ; RV64XVENTANACONDOPS-NEXT:    addi sp, sp, -16
 ; RV64XVENTANACONDOPS-NEXT:    sd ra, 8(sp) # 8-byte Folded Spill
 ; RV64XVENTANACONDOPS-NEXT:    sd s0, 0(sp) # 8-byte Folded Spill
 ; RV64XVENTANACONDOPS-NEXT:    vt.maskcn a3, a3, a0
-; RV64XVENTANACONDOPS-NEXT:    vt.maskc a0, a2, a0
-; RV64XVENTANACONDOPS-NEXT:    or a0, a0, a3
-; RV64XVENTANACONDOPS-NEXT:    slli s0, a0, 48
+; RV64XVENTANACONDOPS-NEXT:    vt.maskc s0, a2, a0
+; RV64XVENTANACONDOPS-NEXT:    or s0, s0, a3
 ; RV64XVENTANACONDOPS-NEXT:    beqz a1, .LBB58_2
 ; RV64XVENTANACONDOPS-NEXT:  # %bb.1:
-; RV64XVENTANACONDOPS-NEXT:    srai a0, s0, 48
+; RV64XVENTANACONDOPS-NEXT:    mv a0, s0
 ; RV64XVENTANACONDOPS-NEXT:    call bat@plt
 ; RV64XVENTANACONDOPS-NEXT:  .LBB58_2:
-; RV64XVENTANACONDOPS-NEXT:    srai a0, s0, 48
+; RV64XVENTANACONDOPS-NEXT:    mv a0, s0
 ; RV64XVENTANACONDOPS-NEXT:    ld ra, 8(sp) # 8-byte Folded Reload
 ; RV64XVENTANACONDOPS-NEXT:    ld s0, 0(sp) # 8-byte Folded Reload
 ; RV64XVENTANACONDOPS-NEXT:    addi sp, sp, 16
 ; RV64XVENTANACONDOPS-NEXT:    ret
 ;
 ; RV64XTHEADCONDMOV-LABEL: numsignbits:
 ; RV64XTHEADCONDMOV:       # %bb.0:
 ; RV64XTHEADCONDMOV-NEXT:    addi sp, sp, -16

 ; RV64XTHEADCONDMOV-NEXT:    ret
 ;
 ; RV32ZICOND-LABEL: numsignbits:
 ; RV32ZICOND:       # %bb.0:
 ; RV32ZICOND-NEXT:    addi sp, sp, -16
 ; RV32ZICOND-NEXT:    sw ra, 12(sp) # 4-byte Folded Spill
 ; RV32ZICOND-NEXT:    sw s0, 8(sp) # 4-byte Folded Spill
 ; RV32ZICOND-NEXT:    czero.nez a3, a3, a0
-; RV32ZICOND-NEXT:    czero.eqz a0, a2, a0
-; RV32ZICOND-NEXT:    or a0, a0, a3
-; RV32ZICOND-NEXT:    slli s0, a0, 16
+; RV32ZICOND-NEXT:    czero.eqz s0, a2, a0
+; RV32ZICOND-NEXT:    or s0, s0, a3
 ; RV32ZICOND-NEXT:    beqz a1, .LBB58_2
 ; RV32ZICOND-NEXT:  # %bb.1:
-; RV32ZICOND-NEXT:    srai a0, s0, 16
+; RV32ZICOND-NEXT:    mv a0, s0
 ; RV32ZICOND-NEXT:    call bat@plt
 ; RV32ZICOND-NEXT:  .LBB58_2:
-; RV32ZICOND-NEXT:    srai a0, s0, 16
+; RV32ZICOND-NEXT:    mv a0, s0
 ; RV32ZICOND-NEXT:    lw ra, 12(sp) # 4-byte Folded Reload
 ; RV32ZICOND-NEXT:    lw s0, 8(sp) # 4-byte Folded Reload
 ; RV32ZICOND-NEXT:    addi sp, sp, 16
 ; RV32ZICOND-NEXT:    ret
 ;
 ; RV64ZICOND-LABEL: numsignbits:
 ; RV64ZICOND:       # %bb.0:
 ; RV64ZICOND-NEXT:    addi sp, sp, -16
 ; RV64ZICOND-NEXT:    sd ra, 8(sp) # 8-byte Folded Spill
 ; RV64ZICOND-NEXT:    sd s0, 0(sp) # 8-byte Folded Spill
 ; RV64ZICOND-NEXT:    czero.nez a3, a3, a0
-; RV64ZICOND-NEXT:    czero.eqz a0, a2, a0
-; RV64ZICOND-NEXT:    or a0, a0, a3
-; RV64ZICOND-NEXT:    slli s0, a0, 48
+; RV64ZICOND-NEXT:    czero.eqz s0, a2, a0
+; RV64ZICOND-NEXT:    or s0, s0, a3
 ; RV64ZICOND-NEXT:    beqz a1, .LBB58_2
 ; RV64ZICOND-NEXT:  # %bb.1:
-; RV64ZICOND-NEXT:    srai a0, s0, 48
+; RV64ZICOND-NEXT:    mv a0, s0
 ; RV64ZICOND-NEXT:    call bat@plt
 ; RV64ZICOND-NEXT:  .LBB58_2:
-; RV64ZICOND-NEXT:    srai a0, s0, 48
+; RV64ZICOND-NEXT:    mv a0, s0
 ; RV64ZICOND-NEXT:    ld ra, 8(sp) # 8-byte Folded Reload
 ; RV64ZICOND-NEXT:    ld s0, 0(sp) # 8-byte Folded Reload
 ; RV64ZICOND-NEXT:    addi sp, sp, 16
 ; RV64ZICOND-NEXT:    ret
   %5 = icmp eq i16 %0, 0
   %6 = select i1 %5, i16 %3, i16 %2
   %7 = icmp eq i16 %1, 0
   br i1 %7, label %9, label %8