Index: llvm/lib/Target/RISCV/RISCVISelLowering.cpp
===================================================================
--- llvm/lib/Target/RISCV/RISCVISelLowering.cpp
+++ llvm/lib/Target/RISCV/RISCVISelLowering.cpp
@@ -156,8 +156,16 @@
     setOperationAction(ISD::ROTR, XLenVT, Expand);
   }
 
-  if (!Subtarget.hasStdExtZbp())
+  if (Subtarget.hasStdExtZbp()) {
+    setOperationAction(ISD::BITREVERSE, XLenVT, Legal);
+
+    if (Subtarget.is64Bit()) {
+      setOperationAction(ISD::BITREVERSE, MVT::i32, Custom);
+      setOperationAction(ISD::BSWAP, MVT::i32, Custom);
+    }
+  } else {
     setOperationAction(ISD::BSWAP, XLenVT, Expand);
+  }
 
   if (!Subtarget.hasStdExtZbb()) {
     setOperationAction(ISD::CTTZ, XLenVT, Expand);
@@ -165,9 +173,6 @@
     setOperationAction(ISD::CTPOP, XLenVT, Expand);
   }
 
-  if (Subtarget.hasStdExtZbp())
-    setOperationAction(ISD::BITREVERSE, XLenVT, Legal);
-
   if (Subtarget.hasStdExtZbt()) {
     setOperationAction(ISD::FSHL, XLenVT, Legal);
     setOperationAction(ISD::FSHR, XLenVT, Legal);
@@ -1052,6 +1057,21 @@
     Results.push_back(DAG.getNode(ISD::TRUNCATE, DL, MVT::i32, NewRes));
     break;
   }
+  case ISD::BSWAP:
+  case ISD::BITREVERSE: {
+    assert(N->getValueType(0) == MVT::i32 && Subtarget.is64Bit() &&
+           Subtarget.hasStdExtZbp() && "Unexpected custom legalisation");
+    SDValue NewOp0 = DAG.getNode(ISD::ANY_EXTEND, DL, MVT::i64,
+                                 N->getOperand(0));
+    unsigned Imm = N->getOpcode() == ISD::BITREVERSE ? 31 : 24;
+    SDValue GREVIW = DAG.getNode(RISCVISD::GREVIW, DL, MVT::i64, NewOp0,
+                                 DAG.getTargetConstant(Imm, DL,
+                                                       Subtarget.getXLenVT()));
+    // ReplaceNodeResults requires we maintain the same type for the return
+    // value.
+    Results.push_back(DAG.getNode(ISD::TRUNCATE, DL, MVT::i32, GREVIW));
+    break;
+  }
   }
 }
 
Index: llvm/lib/Target/RISCV/RISCVInstrInfoB.td
===================================================================
--- llvm/lib/Target/RISCV/RISCVInstrInfoB.td
+++ llvm/lib/Target/RISCV/RISCVInstrInfoB.td
@@ -923,9 +923,6 @@
 let Predicates = [HasStdExtZbp, IsRV64] in {
 def : Pat<(riscv_greviw GPR:$rs1, timm:$shamt), (GREVIW GPR:$rs1, timm:$shamt)>;
 def : Pat<(riscv_gorciw GPR:$rs1, timm:$shamt), (GORCIW GPR:$rs1, timm:$shamt)>;
-
-def : Pat<(sra (bswap GPR:$rs1), (i64 32)), (GREVIW GPR:$rs1, (i64 24))>;
-def : Pat<(sra (bitreverse GPR:$rs1), (i64 32)), (GREVIW GPR:$rs1, (i64 31))>;
 } // Predicates = [HasStdExtZbp, IsRV64]
 
 let Predicates = [HasStdExtZbt, IsRV64] in {
Index: llvm/test/CodeGen/RISCV/rv64Zbp.ll
===================================================================
--- llvm/test/CodeGen/RISCV/rv64Zbp.ll
+++ llvm/test/CodeGen/RISCV/rv64Zbp.ll
@@ -1495,15 +1495,13 @@
 ;
 ; RV64IB-LABEL: bswap_i32_nosext:
 ; RV64IB:       # %bb.0:
-; RV64IB-NEXT:    rev8 a0, a0
-; RV64IB-NEXT:    srli a0, a0, 32
+; RV64IB-NEXT:    greviw a0, a0, 24
 ; RV64IB-NEXT:    sw a0, 0(a1)
 ; RV64IB-NEXT:    ret
 ;
 ; RV64IBP-LABEL: bswap_i32_nosext:
 ; RV64IBP:       # %bb.0:
-; RV64IBP-NEXT:    rev8 a0, a0
-; RV64IBP-NEXT:    srli a0, a0, 32
+; RV64IBP-NEXT:    greviw a0, a0, 24
 ; RV64IBP-NEXT:    sw a0, 0(a1)
 ; RV64IBP-NEXT:    ret
   %1 = tail call i32 @llvm.bswap.i32(i32 %a)
@@ -1756,15 +1754,13 @@
 ;
 ; RV64IB-LABEL: bitreverse_i32_nosext:
 ; RV64IB:       # %bb.0:
-; RV64IB-NEXT:    rev a0, a0
-; RV64IB-NEXT:    srli a0, a0, 32
+; RV64IB-NEXT:    greviw a0, a0, 31
 ; RV64IB-NEXT:    sw a0, 0(a1)
 ; RV64IB-NEXT:    ret
 ;
 ; RV64IBP-LABEL: bitreverse_i32_nosext:
 ; RV64IBP:       # %bb.0:
-; RV64IBP-NEXT:    rev a0, a0
-; RV64IBP-NEXT:    srli a0, a0, 32
+; RV64IBP-NEXT:    greviw a0, a0, 31
 ; RV64IBP-NEXT:    sw a0, 0(a1)
 ; RV64IBP-NEXT:    ret
   %1 = tail call i32 @llvm.bitreverse.i32(i32 %a)