diff --git a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
--- a/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
+++ b/llvm/lib/Target/RISCV/RISCVISelLowering.cpp
@@ -1360,6 +1360,23 @@
     return DAG.getNode(ISD::AND, DL, MVT::i64, NewFMV,
                        DAG.getConstant(~SignBit, DL, MVT::i64));
   }
+  case RISCVISD::GREVI: {
+    // Combine (GREVI (GREVI x, C2), C1) -> (GREVI x, C1^C2) when C1^C2 is
+    // non-zero, and to x when it is. Any repeated GREVI stage undoes itself.
+    SDLoc DL(N);
+    auto GREVSrc = N->getOperand(0);
+    uint64_t ShAmt1 = N->getConstantOperandVal(1);
+    if (GREVSrc->getOpcode() != RISCVISD::GREVI)
+      break;
+    uint64_t ShAmt2 = GREVSrc.getConstantOperandVal(1);
+    GREVSrc = GREVSrc->getOperand(0);
+    uint64_t CombinedShAmt = ShAmt1 ^ ShAmt2;
+    if (CombinedShAmt == 0)
+      return GREVSrc;
+    return DAG.getNode(
+        RISCVISD::GREVI, DL, N->getValueType(0), GREVSrc,
+        DAG.getTargetConstant(CombinedShAmt, DL, Subtarget.getXLenVT()));
+  }
   case ISD::OR:
     if (auto GREV = combineORToGREV(SDValue(N, 0), DCI.DAG, Subtarget))
       return GREV;
diff --git a/llvm/test/CodeGen/RISCV/rv32Zbp.ll b/llvm/test/CodeGen/RISCV/rv32Zbp.ll
--- a/llvm/test/CodeGen/RISCV/rv32Zbp.ll
+++ b/llvm/test/CodeGen/RISCV/rv32Zbp.ll
@@ -498,7 +498,6 @@
   ret i64 %or
 }
 
-; FIXME: we should generate grevi 3 here
 define i32 @grev3_i32(i32 %a) nounwind {
 ; RV32I-LABEL: grev3_i32:
 ; RV32I:       # %bb.0:
@@ -524,14 +523,12 @@
 ;
 ; RV32IB-LABEL: grev3_i32:
 ; RV32IB:       # %bb.0:
-; RV32IB-NEXT:    rev.p a0, a0
-; RV32IB-NEXT:    rev2.n a0, a0
+; RV32IB-NEXT:    rev.n a0, a0
 ; RV32IB-NEXT:    ret
 ;
 ; RV32IBP-LABEL: grev3_i32:
 ; RV32IBP:       # %bb.0:
-; RV32IBP-NEXT:    rev.p a0, a0
-; RV32IBP-NEXT:    rev2.n a0, a0
+; RV32IBP-NEXT:    rev.n a0, a0
 ; RV32IBP-NEXT:    ret
   %and1 = shl i32 %a, 1
   %shl1 = and i32 %and1, -1431655766
@@ -546,7 +543,6 @@
   ret i32 %or2
 }
 
-; FIXME: we should generate grevi 3 here
 define i64 @grev3_i64(i64 %a) nounwind {
 ; RV32I-LABEL: grev3_i64:
 ; RV32I:       # %bb.0:
@@ -582,18 +578,14 @@
 ;
 ; RV32IB-LABEL: grev3_i64:
 ; RV32IB:       # %bb.0:
-; RV32IB-NEXT:    rev.p a1, a1
-; RV32IB-NEXT:    rev.p a0, a0
-; RV32IB-NEXT:    rev2.n a0, a0
-; RV32IB-NEXT:    rev2.n a1, a1
+; RV32IB-NEXT:    rev.n a0, a0
+; RV32IB-NEXT:    rev.n a1, a1
 ; RV32IB-NEXT:    ret
 ;
 ; RV32IBP-LABEL: grev3_i64:
 ; RV32IBP:       # %bb.0:
-; RV32IBP-NEXT:    rev.p a1, a1
-; RV32IBP-NEXT:    rev.p a0, a0
-; RV32IBP-NEXT:    rev2.n a0, a0
-; RV32IBP-NEXT:    rev2.n a1, a1
+; RV32IBP-NEXT:    rev.n a0, a0
+; RV32IBP-NEXT:    rev.n a1, a1
 ; RV32IBP-NEXT:    ret
   %and1 = shl i64 %a, 1
   %shl1 = and i64 %and1, -6148914691236517206
@@ -677,7 +669,6 @@
   ret i64 %or
 }
 
-; FIXME: we should generate grevi 5 here
 define i32 @grev5_i32(i32 %a) nounwind {
 ; RV32I-LABEL: grev5_i32:
 ; RV32I:       # %bb.0:
@@ -703,14 +694,12 @@
 ;
 ; RV32IB-LABEL: grev5_i32:
 ; RV32IB:       # %bb.0:
-; RV32IB-NEXT:    rev.p a0, a0
-; RV32IB-NEXT:    rev4.b a0, a0
+; RV32IB-NEXT:    grevi a0, a0, 5
 ; RV32IB-NEXT:    ret
 ;
 ; RV32IBP-LABEL: grev5_i32:
 ; RV32IBP:       # %bb.0:
-; RV32IBP-NEXT:    rev.p a0, a0
-; RV32IBP-NEXT:    rev4.b a0, a0
+; RV32IBP-NEXT:    grevi a0, a0, 5
 ; RV32IBP-NEXT:    ret
   %and1 = shl i32 %a, 1
   %shl1 = and i32 %and1, -1431655766
@@ -725,7 +714,6 @@
   ret i32 %or2
 }
 
-; FIXME: we should generate grevi 5 here
 define i64 @grev5_i64(i64 %a) nounwind {
 ; RV32I-LABEL: grev5_i64:
 ; RV32I:       # %bb.0:
@@ -761,18 +749,14 @@
 ;
 ; RV32IB-LABEL: grev5_i64:
 ; RV32IB:       # %bb.0:
-; RV32IB-NEXT:    rev.p a1, a1
-; RV32IB-NEXT:    rev.p a0, a0
-; RV32IB-NEXT:    rev4.b a0, a0
-; RV32IB-NEXT:    rev4.b a1, a1
+; RV32IB-NEXT:    grevi a0, a0, 5
+; RV32IB-NEXT:    grevi a1, a1, 5
 ; RV32IB-NEXT:    ret
 ;
 ; RV32IBP-LABEL: grev5_i64:
 ; RV32IBP:       # %bb.0:
-; RV32IBP-NEXT:    rev.p a1, a1
-; RV32IBP-NEXT:    rev.p a0, a0
-; RV32IBP-NEXT:    rev4.b a0, a0
-; RV32IBP-NEXT:    rev4.b a1, a1
+; RV32IBP-NEXT:    grevi a0, a0, 5
+; RV32IBP-NEXT:    grevi a1, a1, 5
 ; RV32IBP-NEXT:    ret
   %and1 = shl i64 %a, 1
   %shl1 = and i64 %and1, -6148914691236517206
@@ -788,7 +772,6 @@
   ret i64 %or2
 }
 
-; FIXME: we should generate grevi 6 here
 define i32 @grev6_i32(i32 %a) nounwind {
 ; RV32I-LABEL: grev6_i32:
 ; RV32I:       # %bb.0:
@@ -814,14 +797,12 @@
 ;
 ; RV32IB-LABEL: grev6_i32:
 ; RV32IB:       # %bb.0:
-; RV32IB-NEXT:    rev2.n a0, a0
-; RV32IB-NEXT:    rev4.b a0, a0
+; RV32IB-NEXT:    rev2.b a0, a0
 ; RV32IB-NEXT:    ret
 ;
 ; RV32IBP-LABEL: grev6_i32:
 ; RV32IBP:       # %bb.0:
-; RV32IBP-NEXT:    rev2.n a0, a0
-; RV32IBP-NEXT:    rev4.b a0, a0
+; RV32IBP-NEXT:    rev2.b a0, a0
 ; RV32IBP-NEXT:    ret
   %and1 = shl i32 %a, 2
   %shl1 = and i32 %and1, -858993460
@@ -836,7 +817,6 @@
   ret i32 %or2
 }
 
-; FIXME: we should generate grevi 6 here
 define i64 @grev6_i64(i64 %a) nounwind {
 ; RV32I-LABEL: grev6_i64:
 ; RV32I:       # %bb.0:
@@ -872,18 +852,14 @@
 ;
 ; RV32IB-LABEL: grev6_i64:
 ; RV32IB:       # %bb.0:
-; RV32IB-NEXT:    rev2.n a1, a1
-; RV32IB-NEXT:    rev2.n a0, a0
-; RV32IB-NEXT:    rev4.b a0, a0
-; RV32IB-NEXT:    rev4.b a1, a1
+; RV32IB-NEXT:    rev2.b a0, a0
+; RV32IB-NEXT:    rev2.b a1, a1
 ; RV32IB-NEXT:    ret
 ;
 ; RV32IBP-LABEL: grev6_i64:
 ; RV32IBP:       # %bb.0:
-; RV32IBP-NEXT:    rev2.n a1, a1
-; RV32IBP-NEXT:    rev2.n a0, a0
-; RV32IBP-NEXT:    rev4.b a0, a0
-; RV32IBP-NEXT:    rev4.b a1, a1
+; RV32IBP-NEXT:    rev2.b a0, a0
+; RV32IBP-NEXT:    rev2.b a1, a1
 ; RV32IBP-NEXT:    ret
   %and1 = shl i64 %a, 2
   %shl1 = and i64 %and1, -3689348814741910324
@@ -898,7 +874,6 @@
   ret i64 %or2
 }
 
-; FIXME: we should generate grevi 7 here
 define i32 @grev7_i32(i32 %a) nounwind {
 ; RV32I-LABEL: grev7_i32:
 ; RV32I:       # %bb.0:
@@ -933,16 +908,12 @@
 ;
 ; RV32IB-LABEL: grev7_i32:
 ; RV32IB:       # %bb.0:
-; RV32IB-NEXT:    rev.p a0, a0
-; RV32IB-NEXT:    rev2.n a0, a0
-; RV32IB-NEXT:    rev4.b a0, a0
+; RV32IB-NEXT:    rev.b a0, a0
 ; RV32IB-NEXT:    ret
 ;
 ; RV32IBP-LABEL: grev7_i32:
 ; RV32IBP:       # %bb.0:
-; RV32IBP-NEXT:    rev.p a0, a0
-; RV32IBP-NEXT:    rev2.n a0, a0
-; RV32IBP-NEXT:    rev4.b a0, a0
+; RV32IBP-NEXT:    rev.b a0, a0
 ; RV32IBP-NEXT:    ret
   %and1 = shl i32 %a, 1
   %shl1 = and i32 %and1, -1431655766
@@ -962,7 +933,6 @@
   ret i32 %or3
 }
 
-; FIXME: we should generate grevi 7 here
 define i64 @grev7_i64(i64 %a) nounwind {
 ; RV32I-LABEL: grev7_i64:
 ; RV32I:       # %bb.0:
@@ -1012,22 +982,14 @@
 ;
 ; RV32IB-LABEL: grev7_i64:
 ; RV32IB:       # %bb.0:
-; RV32IB-NEXT:    rev.p a0, a0
-; RV32IB-NEXT:    rev.p a1, a1
-; RV32IB-NEXT:    rev2.n a1, a1
-; RV32IB-NEXT:    rev2.n a0, a0
-; RV32IB-NEXT:    rev4.b a0, a0
-; RV32IB-NEXT:    rev4.b a1, a1
+; RV32IB-NEXT:    rev.b a0, a0
+; RV32IB-NEXT:    rev.b a1, a1
 ; RV32IB-NEXT:    ret
 ;
 ; RV32IBP-LABEL: grev7_i64:
 ; RV32IBP:       # %bb.0:
-; RV32IBP-NEXT:    rev.p a0, a0
-; RV32IBP-NEXT:    rev.p a1, a1
-; RV32IBP-NEXT:    rev2.n a1, a1
-; RV32IBP-NEXT:    rev2.n a0, a0
-; RV32IBP-NEXT:    rev4.b a0, a0
-; RV32IBP-NEXT:    rev4.b a1, a1
+; RV32IBP-NEXT:    rev.b a0, a0
+; RV32IBP-NEXT:    rev.b a1, a1
 ; RV32IBP-NEXT:    ret
   %and1 = shl i64 %a, 1
   %shl1 = and i64 %and1, -6148914691236517206
@@ -1139,6 +1101,386 @@
   ret i32 %or
 }
 
+
+define i32 @grev3b_i32(i32 %a) nounwind {
+; RV32I-LABEL: grev3b_i32:
+; RV32I:       # %bb.0:
+; RV32I-NEXT:    slli a1, a0, 2
+; RV32I-NEXT:    lui a2, 838861
+; RV32I-NEXT:    addi a2, a2, -820
+; RV32I-NEXT:    and a1, a1, a2
+; RV32I-NEXT:    srli a0, a0, 2
+; RV32I-NEXT:    lui a2, 209715
+; RV32I-NEXT:    addi a2, a2, 819
+; RV32I-NEXT:    and a0, a0, a2
+; RV32I-NEXT:    or a0, a1, a0
+; RV32I-NEXT:    slli a1, a0, 1
+; RV32I-NEXT:    lui a2, 699051
+; RV32I-NEXT:    addi a2, a2, -1366
+; RV32I-NEXT:    and a1, a1, a2
+; RV32I-NEXT:    srli a0, a0, 1
+; RV32I-NEXT:    lui a2, 349525
+; RV32I-NEXT:    addi a2, a2, 1365
+; RV32I-NEXT:    and a0, a0, a2
+; RV32I-NEXT:    or a0, a1, a0
+; RV32I-NEXT:    ret
+;
+; RV32IB-LABEL: grev3b_i32:
+; RV32IB:       # %bb.0:
+; RV32IB-NEXT:    rev.n a0, a0
+; RV32IB-NEXT:    ret
+;
+; RV32IBP-LABEL: grev3b_i32:
+; RV32IBP:       # %bb.0:
+; RV32IBP-NEXT:    rev.n a0, a0
+; RV32IBP-NEXT:    ret
+  %and2 = shl i32 %a, 2
+  %shl2 = and i32 %and2, -858993460
+  %and2b = lshr i32 %a, 2
+  %shr2 = and i32 %and2b, 858993459
+  %or2 = or i32 %shl2, %shr2
+  %and1 = shl i32 %or2, 1
+  %shl1 = and i32 %and1, -1431655766
+  %and1b = lshr i32 %or2, 1
+  %shr1 = and i32 %and1b, 1431655765
+  %or1 = or i32 %shl1, %shr1
+  ret i32 %or1
+}
+
+define i64 @grev3b_i64(i64 %a) nounwind {
+; RV32I-LABEL: grev3b_i64:
+; RV32I:       # %bb.0:
+; RV32I-NEXT:    slli a2, a1, 2
+; RV32I-NEXT:    slli a3, a0, 2
+; RV32I-NEXT:    lui a4, 838861
+; RV32I-NEXT:    addi a4, a4, -820
+; RV32I-NEXT:    and a3, a3, a4
+; RV32I-NEXT:    and a2, a2, a4
+; RV32I-NEXT:    srli a1, a1, 2
+; RV32I-NEXT:    srli a0, a0, 2
+; RV32I-NEXT:    lui a4, 209715
+; RV32I-NEXT:    addi a4, a4, 819
+; RV32I-NEXT:    and a0, a0, a4
+; RV32I-NEXT:    and a1, a1, a4
+; RV32I-NEXT:    or a1, a2, a1
+; RV32I-NEXT:    or a0, a3, a0
+; RV32I-NEXT:    slli a2, a0, 1
+; RV32I-NEXT:    slli a3, a1, 1
+; RV32I-NEXT:    lui a4, 699051
+; RV32I-NEXT:    addi a4, a4, -1366
+; RV32I-NEXT:    and a3, a3, a4
+; RV32I-NEXT:    and a2, a2, a4
+; RV32I-NEXT:    srli a0, a0, 1
+; RV32I-NEXT:    srli a1, a1, 1
+; RV32I-NEXT:    lui a4, 349525
+; RV32I-NEXT:    addi a4, a4, 1365
+; RV32I-NEXT:    and a1, a1, a4
+; RV32I-NEXT:    and a0, a0, a4
+; RV32I-NEXT:    or a0, a2, a0
+; RV32I-NEXT:    or a1, a3, a1
+; RV32I-NEXT:    ret
+;
+; RV32IB-LABEL: grev3b_i64:
+; RV32IB:       # %bb.0:
+; RV32IB-NEXT:    rev.n a0, a0
+; RV32IB-NEXT:    rev.n a1, a1
+; RV32IB-NEXT:    ret
+;
+; RV32IBP-LABEL: grev3b_i64:
+; RV32IBP:       # %bb.0:
+; RV32IBP-NEXT:    rev.n a0, a0
+; RV32IBP-NEXT:    rev.n a1, a1
+; RV32IBP-NEXT:    ret
+  %and2 = shl i64 %a, 2
+  %shl2 = and i64 %and2, -3689348814741910324
+  %and2b = lshr i64 %a, 2
+  %shr2 = and i64 %and2b, 3689348814741910323
+  %or2 = or i64 %shl2, %shr2
+  %and1 = shl i64 %or2, 1
+  %shl1 = and i64 %and1, -6148914691236517206
+  %and1b = lshr i64 %or2, 1
+  %shr1 = and i64 %and1b, 6148914691236517205
+  %or1 = or i64 %shl1, %shr1
+  ret i64 %or1
+}
+
+; grev1, grev2, grev1 -> grev2
+define i32 @grev2b_i32(i32 %a) nounwind {
+; RV32I-LABEL: grev2b_i32:
+; RV32I:       # %bb.0:
+; RV32I-NEXT:    slli a1, a0, 1
+; RV32I-NEXT:    lui a2, 699051
+; RV32I-NEXT:    addi a2, a2, -1366
+; RV32I-NEXT:    and a1, a1, a2
+; RV32I-NEXT:    srli a0, a0, 1
+; RV32I-NEXT:    lui a3, 349525
+; RV32I-NEXT:    addi a3, a3, 1365
+; RV32I-NEXT:    and a0, a0, a3
+; RV32I-NEXT:    or a0, a1, a0
+; RV32I-NEXT:    slli a1, a0, 2
+; RV32I-NEXT:    lui a4, 838861
+; RV32I-NEXT:    addi a4, a4, -820
+; RV32I-NEXT:    and a1, a1, a4
+; RV32I-NEXT:    srli a0, a0, 2
+; RV32I-NEXT:    lui a4, 209715
+; RV32I-NEXT:    addi a4, a4, 819
+; RV32I-NEXT:    and a0, a0, a4
+; RV32I-NEXT:    or a0, a1, a0
+; RV32I-NEXT:    slli a1, a0, 1
+; RV32I-NEXT:    and a1, a1, a2
+; RV32I-NEXT:    srli a0, a0, 1
+; RV32I-NEXT:    and a0, a0, a3
+; RV32I-NEXT:    or a0, a1, a0
+; RV32I-NEXT:    ret
+;
+; RV32IB-LABEL: grev2b_i32:
+; RV32IB:       # %bb.0:
+; RV32IB-NEXT:    rev2.n a0, a0
+; RV32IB-NEXT:    ret
+;
+; RV32IBP-LABEL: grev2b_i32:
+; RV32IBP:       # %bb.0:
+; RV32IBP-NEXT:    rev2.n a0, a0
+; RV32IBP-NEXT:    ret
+  %and1 = shl i32 %a, 1
+  %shl1 = and i32 %and1, -1431655766
+  %and1b = lshr i32 %a, 1
+  %shr1 = and i32 %and1b, 1431655765
+  %or1 = or i32 %shl1, %shr1
+  %and2 = shl i32 %or1, 2
+  %shl2 = and i32 %and2, -858993460
+  %and2b = lshr i32 %or1, 2
+  %shr2 = and i32 %and2b, 858993459
+  %or2 = or i32 %shl2, %shr2
+  %and3 = shl i32 %or2, 1
+  %shl3 = and i32 %and3, -1431655766
+  %and3b = lshr i32 %or2, 1
+  %shr3 = and i32 %and3b, 1431655765
+  %or3 = or i32 %shl3, %shr3
+  ret i32 %or3
+}
+
+; grev1, grev2, grev1 -> grev2
+define i64 @grev2b_i64(i64 %a) nounwind {
+; RV32I-LABEL: grev2b_i64:
+; RV32I:       # %bb.0:
+; RV32I-NEXT:    slli a2, a0, 1
+; RV32I-NEXT:    slli a3, a1, 1
+; RV32I-NEXT:    lui a4, 699051
+; RV32I-NEXT:    addi a4, a4, -1366
+; RV32I-NEXT:    and a3, a3, a4
+; RV32I-NEXT:    and a2, a2, a4
+; RV32I-NEXT:    srli a0, a0, 1
+; RV32I-NEXT:    srli a1, a1, 1
+; RV32I-NEXT:    lui a5, 349525
+; RV32I-NEXT:    addi a5, a5, 1365
+; RV32I-NEXT:    and a1, a1, a5
+; RV32I-NEXT:    and a0, a0, a5
+; RV32I-NEXT:    or a0, a2, a0
+; RV32I-NEXT:    or a1, a3, a1
+; RV32I-NEXT:    slli a6, a1, 2
+; RV32I-NEXT:    slli a3, a0, 2
+; RV32I-NEXT:    lui a2, 838861
+; RV32I-NEXT:    addi a2, a2, -820
+; RV32I-NEXT:    and a7, a3, a2
+; RV32I-NEXT:    and a2, a6, a2
+; RV32I-NEXT:    srli a1, a1, 2
+; RV32I-NEXT:    srli a0, a0, 2
+; RV32I-NEXT:    lui a3, 209715
+; RV32I-NEXT:    addi a3, a3, 819
+; RV32I-NEXT:    and a0, a0, a3
+; RV32I-NEXT:    and a1, a1, a3
+; RV32I-NEXT:    or a1, a2, a1
+; RV32I-NEXT:    or a0, a7, a0
+; RV32I-NEXT:    slli a2, a0, 1
+; RV32I-NEXT:    slli a3, a1, 1
+; RV32I-NEXT:    and a3, a3, a4
+; RV32I-NEXT:    and a2, a2, a4
+; RV32I-NEXT:    srli a0, a0, 1
+; RV32I-NEXT:    srli a1, a1, 1
+; RV32I-NEXT:    and a1, a1, a5
+; RV32I-NEXT:    and a0, a0, a5
+; RV32I-NEXT:    or a0, a2, a0
+; RV32I-NEXT:    or a1, a3, a1
+; RV32I-NEXT:    ret
+;
+; RV32IB-LABEL: grev2b_i64:
+; RV32IB:       # %bb.0:
+; RV32IB-NEXT:    rev2.n a0, a0
+; RV32IB-NEXT:    rev2.n a1, a1
+; RV32IB-NEXT:    ret
+;
+; RV32IBP-LABEL: grev2b_i64:
+; RV32IBP:       # %bb.0:
+; RV32IBP-NEXT:    rev2.n a0, a0
+; RV32IBP-NEXT:    rev2.n a1, a1
+; RV32IBP-NEXT:    ret
+  %and1 = shl i64 %a, 1
+  %shl1 = and i64 %and1, -6148914691236517206
+  %and1b = lshr i64 %a, 1
+  %shr1 = and i64 %and1b, 6148914691236517205
+  %or1 = or i64 %shl1, %shr1
+  %and2 = shl i64 %or1, 2
+  %shl2 = and i64 %and2, -3689348814741910324
+  %and2b = lshr i64 %or1, 2
+  %shr2 = and i64 %and2b, 3689348814741910323
+  %or2 = or i64 %shl2, %shr2
+  %and3 = shl i64 %or2, 1
+  %shl3 = and i64 %and3, -6148914691236517206
+  %and3b = lshr i64 %or2, 1
+  %shr3 = and i64 %and3b, 6148914691236517205
+  %or3 = or i64 %shl3, %shr3
+  ret i64 %or3
+}
+
+; grev1, grev2, grev1, grev2 -> identity
+define i32 @grev0_i32(i32 %a) nounwind {
+; RV32I-LABEL: grev0_i32:
+; RV32I:       # %bb.0:
+; RV32I-NEXT:    slli a1, a0, 1
+; RV32I-NEXT:    lui a2, 699051
+; RV32I-NEXT:    addi a2, a2, -1366
+; RV32I-NEXT:    and a1, a1, a2
+; RV32I-NEXT:    srli a0, a0, 1
+; RV32I-NEXT:    lui a3, 349525
+; RV32I-NEXT:    addi a3, a3, 1365
+; RV32I-NEXT:    and a0, a0, a3
+; RV32I-NEXT:    or a0, a1, a0
+; RV32I-NEXT:    slli a1, a0, 2
+; RV32I-NEXT:    lui a4, 838861
+; RV32I-NEXT:    addi a4, a4, -820
+; RV32I-NEXT:    and a1, a1, a4
+; RV32I-NEXT:    srli a0, a0, 2
+; RV32I-NEXT:    lui a5, 209715
+; RV32I-NEXT:    addi a5, a5, 819
+; RV32I-NEXT:    and a0, a0, a5
+; RV32I-NEXT:    or a0, a1, a0
+; RV32I-NEXT:    slli a1, a0, 1
+; RV32I-NEXT:    and a1, a1, a2
+; RV32I-NEXT:    srli a0, a0, 1
+; RV32I-NEXT:    and a0, a0, a3
+; RV32I-NEXT:    or a0, a1, a0
+; RV32I-NEXT:    slli a1, a0, 2
+; RV32I-NEXT:    and a1, a1, a4
+; RV32I-NEXT:    srli a0, a0, 2
+; RV32I-NEXT:    and a0, a0, a5
+; RV32I-NEXT:    or a0, a1, a0
+; RV32I-NEXT:    ret
+;
+; RV32IB-LABEL: grev0_i32:
+; RV32IB:       # %bb.0:
+; RV32IB-NEXT:    ret
+;
+; RV32IBP-LABEL: grev0_i32:
+; RV32IBP:       # %bb.0:
+; RV32IBP-NEXT:    ret
+  %and1 = shl i32 %a, 1
+  %shl1 = and i32 %and1, -1431655766
+  %and1b = lshr i32 %a, 1
+  %shr1 = and i32 %and1b, 1431655765
+  %or1 = or i32 %shl1, %shr1
+  %and2 = shl i32 %or1, 2
+  %shl2 = and i32 %and2, -858993460
+  %and2b = lshr i32 %or1, 2
+  %shr2 = and i32 %and2b, 858993459
+  %or2 = or i32 %shl2, %shr2
+  %and3 = shl i32 %or2, 1
+  %shl3 = and i32 %and3, -1431655766
+  %and3b = lshr i32 %or2, 1
+  %shr3 = and i32 %and3b, 1431655765
+  %or3 = or i32 %shl3, %shr3
+  %and4 = shl i32 %or3, 2
+  %shl4 = and i32 %and4, -858993460
+  %and4b = lshr i32 %or3, 2
+  %shr4 = and i32 %and4b, 858993459
+  %or4 = or i32 %shl4, %shr4
+  ret i32 %or4
+}
+
+; grev1, grev2, grev1, grev2 -> identity
+define i64 @grev0_i64(i64 %a) nounwind {
+; RV32I-LABEL: grev0_i64:
+; RV32I:       # %bb.0:
+; RV32I-NEXT:    slli a2, a1, 1
+; RV32I-NEXT:    slli a3, a0, 1
+; RV32I-NEXT:    lui a4, 699051
+; RV32I-NEXT:    addi a4, a4, -1366
+; RV32I-NEXT:    and a3, a3, a4
+; RV32I-NEXT:    and a2, a2, a4
+; RV32I-NEXT:    srli a1, a1, 1
+; RV32I-NEXT:    srli a0, a0, 1
+; RV32I-NEXT:    lui a5, 349525
+; RV32I-NEXT:    addi a5, a5, 1365
+; RV32I-NEXT:    and a0, a0, a5
+; RV32I-NEXT:    and a1, a1, a5
+; RV32I-NEXT:    or a1, a2, a1
+; RV32I-NEXT:    or a0, a3, a0
+; RV32I-NEXT:    slli a6, a0, 2
+; RV32I-NEXT:    slli a3, a1, 2
+; RV32I-NEXT:    lui a2, 838861
+; RV32I-NEXT:    addi a2, a2, -820
+; RV32I-NEXT:    and a7, a3, a2
+; RV32I-NEXT:    and a6, a6, a2
+; RV32I-NEXT:    srli a0, a0, 2
+; RV32I-NEXT:    srli a1, a1, 2
+; RV32I-NEXT:    lui a3, 209715
+; RV32I-NEXT:    addi a3, a3, 819
+; RV32I-NEXT:    and a1, a1, a3
+; RV32I-NEXT:    and a0, a0, a3
+; RV32I-NEXT:    or t0, a6, a0
+; RV32I-NEXT:    or a1, a7, a1
+; RV32I-NEXT:    slli a6, a1, 1
+; RV32I-NEXT:    slli a0, t0, 1
+; RV32I-NEXT:    and a7, a0, a4
+; RV32I-NEXT:    and a4, a6, a4
+; RV32I-NEXT:    srli a1, a1, 1
+; RV32I-NEXT:    srli a0, t0, 1
+; RV32I-NEXT:    and a0, a0, a5
+; RV32I-NEXT:    and a1, a1, a5
+; RV32I-NEXT:    or a1, a4, a1
+; RV32I-NEXT:    or a0, a7, a0
+; RV32I-NEXT:    slli a4, a0, 2
+; RV32I-NEXT:    slli a5, a1, 2
+; RV32I-NEXT:    and a5, a5, a2
+; RV32I-NEXT:    and a2, a4, a2
+; RV32I-NEXT:    srli a0, a0, 2
+; RV32I-NEXT:    srli a1, a1, 2
+; RV32I-NEXT:    and a1, a1, a3
+; RV32I-NEXT:    and a0, a0, a3
+; RV32I-NEXT:    or a0, a2, a0
+; RV32I-NEXT:    or a1, a5, a1
+; RV32I-NEXT:    ret
+;
+; RV32IB-LABEL: grev0_i64:
+; RV32IB:       # %bb.0:
+; RV32IB-NEXT:    ret
+;
+; RV32IBP-LABEL: grev0_i64:
+; RV32IBP:       # %bb.0:
+; RV32IBP-NEXT:    ret
+  %and1 = shl i64 %a, 1
+  %shl1 = and i64 %and1, -6148914691236517206
+  %and1b = lshr i64 %a, 1
+  %shr1 = and i64 %and1b, 6148914691236517205
+  %or1 = or i64 %shl1, %shr1
+  %and2 = shl i64 %or1, 2
+  %shl2 = and i64 %and2, -3689348814741910324
+  %and2b = lshr i64 %or1, 2
+  %shr2 = and i64 %and2b, 3689348814741910323
+  %or2 = or i64 %shl2, %shr2
+  %and3 = shl i64 %or2, 1
+  %shl3 = and i64 %and3, -6148914691236517206
+  %and3b = lshr i64 %or2, 1
+  %shr3 = and i64 %and3b, 6148914691236517205
+  %or3 = or i64 %shl3, %shr3
+  %and4 = shl i64 %or3, 2
+  %shl4 = and i64 %and4, -3689348814741910324
+  %and4b = lshr i64 %or3, 2
+  %shr4 = and i64 %and4b, 3689348814741910323
+  %or4 = or i64 %shl4, %shr4
+  ret i64 %or4
+}
+
 declare i32 @llvm.fshl.i32(i32, i32, i32)
 declare i32 @llvm.fshr.i32(i32, i32, i32)
 
diff --git a/llvm/test/CodeGen/RISCV/rv64Zbp.ll b/llvm/test/CodeGen/RISCV/rv64Zbp.ll
--- a/llvm/test/CodeGen/RISCV/rv64Zbp.ll
+++ b/llvm/test/CodeGen/RISCV/rv64Zbp.ll
@@ -571,7 +571,6 @@
   ret i64 %or
 }
 
-; FIXME: we should generate greviw 3 here
 define signext i32 @grev3_i32(i32 signext %a) nounwind {
 ; RV64I-LABEL: grev3_i32:
 ; RV64I:       # %bb.0:
@@ -600,14 +599,12 @@
 ;
 ; RV64IB-LABEL: grev3_i32:
 ; RV64IB:       # %bb.0:
-; RV64IB-NEXT:    greviw a0, a0, 1
-; RV64IB-NEXT:    greviw a0, a0, 2
+; RV64IB-NEXT:    greviw a0, a0, 3
 ; RV64IB-NEXT:    ret
 ;
 ; RV64IBP-LABEL: grev3_i32:
 ; RV64IBP:       # %bb.0:
-; RV64IBP-NEXT:    greviw a0, a0, 1
-; RV64IBP-NEXT:    greviw a0, a0, 2
+; RV64IBP-NEXT:    greviw a0, a0, 3
 ; RV64IBP-NEXT:    ret
   %and1 = shl i32 %a, 1
   %shl1 = and i32 %and1, -1431655766
@@ -622,7 +619,6 @@
   ret i32 %or2
 }
 
-; FIXME: we should generate grevi 3 here
 define i64 @grev3_i64(i64 %a) nounwind {
 ; RV64I-LABEL: grev3_i64:
 ; RV64I:       # %bb.0:
@@ -672,14 +668,12 @@
 ;
 ; RV64IB-LABEL: grev3_i64:
 ; RV64IB:       # %bb.0:
-; RV64IB-NEXT:    rev.p a0, a0
-; RV64IB-NEXT:    rev2.n a0, a0
+; RV64IB-NEXT:    rev.n a0, a0
 ; RV64IB-NEXT:    ret
 ;
 ; RV64IBP-LABEL: grev3_i64:
 ; RV64IBP:       # %bb.0:
-; RV64IBP-NEXT:    rev.p a0, a0
-; RV64IBP-NEXT:    rev2.n a0, a0
+; RV64IBP-NEXT:    rev.n a0, a0
 ; RV64IBP-NEXT:    ret
   %and1 = shl i64 %a, 1
   %shl1 = and i64 %and1, -6148914691236517206
@@ -771,7 +765,6 @@
   ret i64 %or
 }
 
-; FIXME: we should generate greviw 5 here
 define signext i32 @grev5_i32(i32 signext %a) nounwind {
 ; RV64I-LABEL: grev5_i32:
 ; RV64I:       # %bb.0:
@@ -800,14 +793,12 @@
 ;
 ; RV64IB-LABEL: grev5_i32:
 ; RV64IB:       # %bb.0:
-; RV64IB-NEXT:    greviw a0, a0, 1
-; RV64IB-NEXT:    greviw a0, a0, 4
+; RV64IB-NEXT:    greviw a0, a0, 5
 ; RV64IB-NEXT:    ret
 ;
 ; RV64IBP-LABEL: grev5_i32:
 ; RV64IBP:       # %bb.0:
-; RV64IBP-NEXT:    greviw a0, a0, 1
-; RV64IBP-NEXT:    greviw a0, a0, 4
+; RV64IBP-NEXT:    greviw a0, a0, 5
 ; RV64IBP-NEXT:    ret
   %and1 = shl i32 %a, 1
   %shl1 = and i32 %and1, -1431655766
@@ -822,7 +813,6 @@
   ret i32 %or2
 }
 
-; FIXME: we should generate grevi 5 here
 define i64 @grev5_i64(i64 %a) nounwind {
 ; RV64I-LABEL: grev5_i64:
 ; RV64I:       # %bb.0:
@@ -872,14 +862,12 @@
 ;
 ; RV64IB-LABEL: grev5_i64:
 ; RV64IB:       # %bb.0:
-; RV64IB-NEXT:    rev.p a0, a0
-; RV64IB-NEXT:    rev4.b a0, a0
+; RV64IB-NEXT:    grevi a0, a0, 5
 ; RV64IB-NEXT:    ret
 ;
 ; RV64IBP-LABEL: grev5_i64:
 ; RV64IBP:       # %bb.0:
-; RV64IBP-NEXT:    rev.p a0, a0
-; RV64IBP-NEXT:    rev4.b a0, a0
+; RV64IBP-NEXT:    grevi a0, a0, 5
 ; RV64IBP-NEXT:    ret
   %and1 = shl i64 %a, 1
   %shl1 = and i64 %and1, -6148914691236517206
@@ -895,7 +883,6 @@
   ret i64 %or2
 }
 
-; FIXME: we should generate greviw 6 here
 define signext i32 @grev6_i32(i32 signext %a) nounwind {
 ; RV64I-LABEL: grev6_i32:
 ; RV64I:       # %bb.0:
@@ -924,14 +911,12 @@
 ;
 ; RV64IB-LABEL: grev6_i32:
 ; RV64IB:       # %bb.0:
-; RV64IB-NEXT:    greviw a0, a0, 2
-; RV64IB-NEXT:    greviw a0, a0, 4
+; RV64IB-NEXT:    greviw a0, a0, 6
 ; RV64IB-NEXT:    ret
 ;
 ; RV64IBP-LABEL: grev6_i32:
 ; RV64IBP:       # %bb.0:
-; RV64IBP-NEXT:    greviw a0, a0, 2
-; RV64IBP-NEXT:    greviw a0, a0, 4
+; RV64IBP-NEXT:    greviw a0, a0, 6
 ; RV64IBP-NEXT:    ret
   %and1 = shl i32 %a, 2
   %shl1 = and i32 %and1, -858993460
@@ -946,7 +931,6 @@
   ret i32 %or2
 }
 
-; FIXME: we should generate grevi 6 here
 define i64 @grev6_i64(i64 %a) nounwind {
 ; RV64I-LABEL: grev6_i64:
 ; RV64I:       # %bb.0:
@@ -996,14 +980,12 @@
 ;
 ; RV64IB-LABEL: grev6_i64:
 ; RV64IB:       # %bb.0:
-; RV64IB-NEXT:    rev2.n a0, a0
-; RV64IB-NEXT:    rev4.b a0, a0
+; RV64IB-NEXT:    rev2.b a0, a0
 ; RV64IB-NEXT:    ret
 ;
 ; RV64IBP-LABEL: grev6_i64:
 ; RV64IBP:       # %bb.0:
-; RV64IBP-NEXT:    rev2.n a0, a0
-; RV64IBP-NEXT:    rev4.b a0, a0
+; RV64IBP-NEXT:    rev2.b a0, a0
 ; RV64IBP-NEXT:    ret
   %and1 = shl i64 %a, 2
   %shl1 = and i64 %and1, -3689348814741910324
@@ -1018,7 +1000,6 @@
   ret i64 %or2
 }
 
-; FIXME: we should generate greviw 7 here
 define signext i32 @grev7_i32(i32 signext %a) nounwind {
 ; RV64I-LABEL: grev7_i32:
 ; RV64I:       # %bb.0:
@@ -1056,16 +1037,12 @@
 ;
 ; RV64IB-LABEL: grev7_i32:
 ; RV64IB:       # %bb.0:
-; RV64IB-NEXT:    greviw a0, a0, 1
-; RV64IB-NEXT:    greviw a0, a0, 2
-; RV64IB-NEXT:    greviw a0, a0, 4
+; RV64IB-NEXT:    greviw a0, a0, 7
 ; RV64IB-NEXT:    ret
 ;
 ; RV64IBP-LABEL: grev7_i32:
 ; RV64IBP:       # %bb.0:
-; RV64IBP-NEXT:    greviw a0, a0, 1
-; RV64IBP-NEXT:    greviw a0, a0, 2
-; RV64IBP-NEXT:    greviw a0, a0, 4
+; RV64IBP-NEXT:    greviw a0, a0, 7
 ; RV64IBP-NEXT:    ret
   %and1 = shl i32 %a, 1
   %shl1 = and i32 %and1, -1431655766
@@ -1085,7 +1062,6 @@
   ret i32 %or3
 }
 
-; FIXME: we should generate grevi 7 here
 define i64 @grev7_i64(i64 %a) nounwind {
 ; RV64I-LABEL: grev7_i64:
 ; RV64I:       # %bb.0:
@@ -1156,16 +1132,12 @@
 ;
 ; RV64IB-LABEL: grev7_i64:
 ; RV64IB:       # %bb.0:
-; RV64IB-NEXT:    rev.p a0, a0
-; RV64IB-NEXT:    rev2.n a0, a0
-; RV64IB-NEXT:    rev4.b a0, a0
+; RV64IB-NEXT:    rev.b a0, a0
 ; RV64IB-NEXT:    ret
 ;
 ; RV64IBP-LABEL: grev7_i64:
 ; RV64IBP:       # %bb.0:
-; RV64IBP-NEXT:    rev.p a0, a0
-; RV64IBP-NEXT:    rev2.n a0, a0
-; RV64IBP-NEXT:    rev4.b a0, a0
+; RV64IBP-NEXT:    rev.b a0, a0
 ; RV64IBP-NEXT:    ret
   %and1 = shl i64 %a, 1
   %shl1 = and i64 %and1, -6148914691236517206
@@ -1390,6 +1362,421 @@
   ret i64 %or
 }
 
+define signext i32 @grev3b_i32(i32 signext %a) nounwind {
+; RV64I-LABEL: grev3b_i32:
+; RV64I:       # %bb.0:
+; RV64I-NEXT:    slli a1, a0, 2
+; RV64I-NEXT:    lui a2, 838861
+; RV64I-NEXT:    addiw a2, a2, -820
+; RV64I-NEXT:    and a1, a1, a2
+; RV64I-NEXT:    srli a0, a0, 2
+; RV64I-NEXT:    lui a2, 209715
+; RV64I-NEXT:    addiw a2, a2, 819
+; RV64I-NEXT:    and a0, a0, a2
+; RV64I-NEXT:    or a0, a1, a0
+; RV64I-NEXT:    slli a1, a0, 1
+; RV64I-NEXT:    lui a2, 171
+; RV64I-NEXT:    addiw a2, a2, -1365
+; RV64I-NEXT:    slli a2, a2, 12
+; RV64I-NEXT:    addi a2, a2, -1366
+; RV64I-NEXT:    and a1, a1, a2
+; RV64I-NEXT:    srli a0, a0, 1
+; RV64I-NEXT:    lui a2, 349525
+; RV64I-NEXT:    addiw a2, a2, 1365
+; RV64I-NEXT:    and a0, a0, a2
+; RV64I-NEXT:    or a0, a1, a0
+; RV64I-NEXT:    sext.w a0, a0
+; RV64I-NEXT:    ret
+;
+; RV64IB-LABEL: grev3b_i32:
+; RV64IB:       # %bb.0:
+; RV64IB-NEXT:    greviw a0, a0, 3
+; RV64IB-NEXT:    ret
+;
+; RV64IBP-LABEL: grev3b_i32:
+; RV64IBP:       # %bb.0:
+; RV64IBP-NEXT:    greviw a0, a0, 3
+; RV64IBP-NEXT:    ret
+  %and2 = shl i32 %a, 2
+  %shl2 = and i32 %and2, -858993460
+  %and2b = lshr i32 %a, 2
+  %shr2 = and i32 %and2b, 858993459
+  %or2 = or i32 %shl2, %shr2
+  %and1 = shl i32 %or2, 1
+  %shl1 = and i32 %and1, -1431655766
+  %and1b = lshr i32 %or2, 1
+  %shr1 = and i32 %and1b, 1431655765
+  %or1 = or i32 %shl1, %shr1
+  ret i32 %or1
+}
+
+define i64 @grev3b_i64(i64 %a) nounwind {
+; RV64I-LABEL: grev3b_i64:
+; RV64I:       # %bb.0:
+; RV64I-NEXT:    slli a1, a0, 2
+; RV64I-NEXT:    lui a2, 1035469
+; RV64I-NEXT:    addiw a2, a2, -819
+; RV64I-NEXT:    slli a2, a2, 12
+; RV64I-NEXT:    addi a2, a2, -819
+; RV64I-NEXT:    slli a2, a2, 12
+; RV64I-NEXT:    addi a2, a2, -819
+; RV64I-NEXT:    slli a2, a2, 12
+; RV64I-NEXT:    addi a2, a2, -820
+; RV64I-NEXT:    and a1, a1, a2
+; RV64I-NEXT:    srli a0, a0, 2
+; RV64I-NEXT:    lui a2, 13107
+; RV64I-NEXT:    addiw a2, a2, 819
+; RV64I-NEXT:    slli a2, a2, 12
+; RV64I-NEXT:    addi a2, a2, 819
+; RV64I-NEXT:    slli a2, a2, 12
+; RV64I-NEXT:    addi a2, a2, 819
+; RV64I-NEXT:    slli a2, a2, 12
+; RV64I-NEXT:    addi a2, a2, 819
+; RV64I-NEXT:    and a0, a0, a2
+; RV64I-NEXT:    or a0, a1, a0
+; RV64I-NEXT:    slli a1, a0, 1
+; RV64I-NEXT:    lui a2, 1026731
+; RV64I-NEXT:    addiw a2, a2, -1365
+; RV64I-NEXT:    slli a2, a2, 12
+; RV64I-NEXT:    addi a2, a2, -1365
+; RV64I-NEXT:    slli a2, a2, 12
+; RV64I-NEXT:    addi a2, a2, -1365
+; RV64I-NEXT:    slli a2, a2, 12
+; RV64I-NEXT:    addi a2, a2, -1366
+; RV64I-NEXT:    and a1, a1, a2
+; RV64I-NEXT:    srli a0, a0, 1
+; RV64I-NEXT:    lui a2, 21845
+; RV64I-NEXT:    addiw a2, a2, 1365
+; RV64I-NEXT:    slli a2, a2, 12
+; RV64I-NEXT:    addi a2, a2, 1365
+; RV64I-NEXT:    slli a2, a2, 12
+; RV64I-NEXT:    addi a2, a2, 1365
+; RV64I-NEXT:    slli a2, a2, 12
+; RV64I-NEXT:    addi a2, a2, 1365
+; RV64I-NEXT:    and a0, a0, a2
+; RV64I-NEXT:    or a0, a1, a0
+; RV64I-NEXT:    ret
+;
+; RV64IB-LABEL: grev3b_i64:
+; RV64IB:       # %bb.0:
+; RV64IB-NEXT:    rev.n a0, a0
+; RV64IB-NEXT:    ret
+;
+; RV64IBP-LABEL: grev3b_i64:
+; RV64IBP:       # %bb.0:
+; RV64IBP-NEXT:    rev.n a0, a0
+; RV64IBP-NEXT:    ret
+  %and2 = shl i64 %a, 2
+  %shl2 = and i64 %and2, -3689348814741910324
+  %and2b = lshr i64 %a, 2
+  %shr2 = and i64 %and2b, 3689348814741910323
+  %or2 = or i64 %shl2, %shr2
+  %and1 = shl i64 %or2, 1
+  %shl1 = and i64 %and1, -6148914691236517206
+  %and1b = lshr i64 %or2, 1
+  %shr1 = and i64 %and1b, 6148914691236517205
+  %or1 = or i64 %shl1, %shr1
+  ret i64 %or1
+}
+
+; grev1, grev2, grev1 -> grev2
+define signext i32 @grev2b_i32(i32 signext %a) nounwind {
+; RV64I-LABEL: grev2b_i32:
+; RV64I:       # %bb.0:
+; RV64I-NEXT:    slli a1, a0, 1
+; RV64I-NEXT:    lui a2, 699051
+; RV64I-NEXT:    addiw a2, a2, -1366
+; RV64I-NEXT:    and a1, a1, a2
+; RV64I-NEXT:    srli a0, a0, 1
+; RV64I-NEXT:    lui a2, 349525
+; RV64I-NEXT:    addiw a2, a2, 1365
+; RV64I-NEXT:    and a0, a0, a2
+; RV64I-NEXT:    or a0, a1, a0
+; RV64I-NEXT:    slli a1, a0, 2
+; RV64I-NEXT:    lui a3, 838861
+; RV64I-NEXT:    addiw a3, a3, -820
+; RV64I-NEXT:    and a1, a1, a3
+; RV64I-NEXT:    srli a0, a0, 2
+; RV64I-NEXT:    lui a3, 209715
+; RV64I-NEXT:    addiw a3, a3, 819
+; RV64I-NEXT:    and a0, a0, a3
+; RV64I-NEXT:    or a0, a1, a0
+; RV64I-NEXT:    slli a1, a0, 1
+; RV64I-NEXT:    lui a3, 171
+; RV64I-NEXT:    addiw a3, a3, -1365
+; RV64I-NEXT:    slli a3, a3, 12
+; RV64I-NEXT:    addi a3, a3, -1366
+; RV64I-NEXT:    and a1, a1, a3
+; RV64I-NEXT:    srli a0, a0, 1
+; RV64I-NEXT:    and a0, a0, a2
+; RV64I-NEXT:    or a0, a1, a0
+; RV64I-NEXT:    sext.w a0, a0
+; RV64I-NEXT:    ret
+;
+; RV64IB-LABEL: grev2b_i32:
+; RV64IB:       # %bb.0:
+; RV64IB-NEXT:    greviw a0, a0, 2
+; RV64IB-NEXT:    ret
+;
+; RV64IBP-LABEL: grev2b_i32:
+; RV64IBP:       # %bb.0:
+; RV64IBP-NEXT:    greviw a0, a0, 2
+; RV64IBP-NEXT:    ret
+  %and1 = shl i32 %a, 1
+  %shl1 = and i32 %and1, -1431655766
+  %and1b = lshr i32 %a, 1
+  %shr1 = and i32 %and1b, 1431655765
+  %or1 = or i32 %shl1, %shr1
+  %and2 = shl i32 %or1, 2
+  %shl2 = and i32 %and2, -858993460
+  %and2b = lshr i32 %or1, 2
+  %shr2 = and i32 %and2b, 858993459
+  %or2 = or i32 %shl2, %shr2
+  %and3 = shl i32 %or2, 1
+  %shl3 = and i32 %and3, -1431655766
+  %and3b = lshr i32 %or2, 1
+  %shr3 = and i32 %and3b, 1431655765
+  %or3 = or i32 %shl3, %shr3
+  ret i32 %or3
+}
+
+; grev1, grev2, grev1 -> grev2
+define i64 @grev2b_i64(i64 %a) nounwind {
+; RV64I-LABEL: grev2b_i64:
+; RV64I:       # %bb.0:
+; RV64I-NEXT:    slli a1, a0, 1
+; RV64I-NEXT:    lui a2, 1026731
+; RV64I-NEXT:    addiw a2, a2, -1365
+; RV64I-NEXT:    slli a2, a2, 12
+; RV64I-NEXT:    addi a2, a2, -1365
+; RV64I-NEXT:    slli a2, a2, 12
+; RV64I-NEXT:    addi a2, a2, -1365
+; RV64I-NEXT:    slli a2, a2, 12
+; RV64I-NEXT:    addi a2, a2, -1366
+; RV64I-NEXT:    and a1, a1, a2
+; RV64I-NEXT:    srli a0, a0, 1
+; RV64I-NEXT:    lui a3, 21845
+; RV64I-NEXT:    addiw a3, a3, 1365
+; RV64I-NEXT:    slli a3, a3, 12
+; RV64I-NEXT:    addi a3, a3, 1365
+; RV64I-NEXT:    slli a3, a3, 12
+; RV64I-NEXT:    addi a3, a3, 1365
+; RV64I-NEXT:    slli a3, a3, 12
+; RV64I-NEXT:    addi a3, a3, 1365
+; RV64I-NEXT:    and a0, a0, a3
+; RV64I-NEXT:    or a0, a1, a0
+; RV64I-NEXT:    slli a1, a0, 2
+; RV64I-NEXT:    lui a4, 1035469
+; RV64I-NEXT:    addiw a4, a4, -819
+; RV64I-NEXT:    slli a4, a4, 12
+; RV64I-NEXT:    addi a4, a4, -819
+; RV64I-NEXT:    slli a4, a4, 12
+; RV64I-NEXT:    addi a4, a4, -819
+; RV64I-NEXT:    slli a4, a4, 12
+; RV64I-NEXT:    addi a4, a4, -820
+; RV64I-NEXT:    and a1, a1, a4
+; RV64I-NEXT:    srli a0, a0, 2
+; RV64I-NEXT:    lui a4, 13107
+; RV64I-NEXT:    addiw a4, a4, 819
+; RV64I-NEXT:    slli a4, a4, 12
+; RV64I-NEXT:    addi a4, a4, 819
+; RV64I-NEXT:    slli a4, a4, 12
+; RV64I-NEXT:    addi a4, a4, 819
+; RV64I-NEXT:    slli a4, a4, 12
+; RV64I-NEXT:    addi a4, a4, 819
+; RV64I-NEXT:    and a0, a0, a4
+; RV64I-NEXT:    or a0, a1, a0
+; RV64I-NEXT:    slli a1, a0, 1
+; RV64I-NEXT:    and a1, a1, a2
+; RV64I-NEXT:    srli a0, a0, 1
+; RV64I-NEXT:    and a0, a0, a3
+; RV64I-NEXT:    or a0, a1, a0
+; RV64I-NEXT:    ret
+;
+; RV64IB-LABEL: grev2b_i64:
+; RV64IB:       # %bb.0:
+; RV64IB-NEXT:    rev2.n a0, a0
+; RV64IB-NEXT:    ret
+;
+; RV64IBP-LABEL: grev2b_i64:
+; RV64IBP:       # %bb.0:
+; RV64IBP-NEXT:    rev2.n a0, a0
+; RV64IBP-NEXT:    ret
+  %and1 = shl i64 %a, 1
+  %shl1 = and i64 %and1, -6148914691236517206
+  %and1b = lshr i64 %a, 1
+  %shr1 = and i64 %and1b, 6148914691236517205
+  %or1 = or i64 %shl1, %shr1
+  %and2 = shl i64 %or1, 2
+  %shl2 = and i64 %and2, -3689348814741910324
+  %and2b = lshr i64 %or1, 2
+  %shr2 = and i64 %and2b, 3689348814741910323
+  %or2 = or i64 %shl2, %shr2
+  %and3 = shl i64 %or2, 1
+  %shl3 = and i64 %and3, -6148914691236517206
+  %and3b = lshr i64 %or2, 1
+  %shr3 = and i64 %and3b, 6148914691236517205
+  %or3 = or i64 %shl3, %shr3
+  ret i64 %or3
+}
+
+; grev1, grev2, grev1, grev2 -> identity
+define signext i32 @grev0_i32(i32 signext %a) nounwind {
+; RV64I-LABEL: grev0_i32:
+; RV64I:       # %bb.0:
+; RV64I-NEXT:    slli a1, a0, 1
+; RV64I-NEXT:    lui a2, 699051
+; RV64I-NEXT:    addiw a2, a2, -1366
+; RV64I-NEXT:    and a1, a1, a2
+; RV64I-NEXT:    srli a0, a0, 1
+; RV64I-NEXT:    lui a3, 349525
+; RV64I-NEXT:    addiw a3, a3, 1365
+; RV64I-NEXT:    and a0, a0, a3
+; RV64I-NEXT:    or a0, a1, a0
+; RV64I-NEXT:    slli a1, a0, 2
+; RV64I-NEXT:    lui a4, 838861
+; RV64I-NEXT:    addiw a4, a4, -820
+; RV64I-NEXT:    and a1, a1, a4
+; RV64I-NEXT:    srli a0, a0, 2
+; RV64I-NEXT:    lui a4, 209715
+; RV64I-NEXT:    addiw a4, a4, 819
+; RV64I-NEXT:    and a0, a0, a4
+; RV64I-NEXT:    or a0, a1, a0
+; RV64I-NEXT:    slli a1, a0, 1
+; RV64I-NEXT:    and a1, a1, a2
+; RV64I-NEXT:    srli a0, a0, 1
+; RV64I-NEXT:    and a0, a0, a3
+; RV64I-NEXT:    or a0, a1, a0
+; RV64I-NEXT:    slli a1, a0, 2
+; RV64I-NEXT:    lui a2, 205
+; RV64I-NEXT:    addiw a2, a2, -819
+; RV64I-NEXT:    slli a2, a2, 12
+; RV64I-NEXT:    addi a2, a2, -820
+; RV64I-NEXT:    and a1, a1, a2
+; RV64I-NEXT:    srli a0, a0, 2
+; RV64I-NEXT:    and a0, a0, a4
+; RV64I-NEXT:    or a0, a1, a0
+; RV64I-NEXT:    sext.w a0, a0
+; RV64I-NEXT:    ret
+;
+; RV64IB-LABEL: grev0_i32:
+; RV64IB:       # %bb.0:
+; RV64IB-NEXT:    ret
+;
+; RV64IBP-LABEL: grev0_i32:
+; RV64IBP:       # %bb.0:
+; RV64IBP-NEXT:    ret
+  %and1 = shl i32 %a, 1
+  %shl1 = and i32 %and1, -1431655766
+  %and1b = lshr i32 %a, 1
+  %shr1 = and i32 %and1b, 1431655765
+  %or1 = or i32 %shl1, %shr1
+  %and2 = shl i32 %or1, 2
+  %shl2 = and i32 %and2, -858993460
+  %and2b = lshr i32 %or1, 2
+  %shr2 = and i32 %and2b, 858993459
+  %or2 = or i32 %shl2, %shr2
+  %and3 = shl i32 %or2, 1
+  %shl3 = and i32 %and3, -1431655766
+  %and3b = lshr i32 %or2, 1
+  %shr3 = and i32 %and3b, 1431655765
+  %or3 = or i32 %shl3, %shr3
+  %and4 = shl i32 %or3, 2
+  %shl4 = and i32 %and4, -858993460
+  %and4b = lshr i32 %or3, 2
+  %shr4 = and i32 %and4b, 858993459
+  %or4 = or i32 %shl4, %shr4
+  ret i32 %or4
+}
+
+; grev1, grev2, grev1, grev2 -> identity
+define i64 @grev0_i64(i64 %a) nounwind {
+; RV64I-LABEL: grev0_i64:
+; RV64I:       # %bb.0:
+; RV64I-NEXT:    slli a1, a0, 1
+; RV64I-NEXT:    lui a2, 1026731
+; RV64I-NEXT:    addiw a2, a2, -1365
+; RV64I-NEXT:    slli a2, a2, 12
+; RV64I-NEXT:    addi a2, a2, -1365
+; RV64I-NEXT:    slli a2, a2, 12
+; RV64I-NEXT:    addi a2, a2, -1365
+; RV64I-NEXT:    slli a2, a2, 12
+; RV64I-NEXT:    addi a2, a2, -1366
+; RV64I-NEXT:    and a1, a1, a2
+; RV64I-NEXT:    srli a0, a0, 1
+; RV64I-NEXT:    lui a3, 21845
+; RV64I-NEXT:    addiw a3, a3, 1365
+; RV64I-NEXT:    slli a3, a3, 12
+; RV64I-NEXT:    addi a3, a3, 1365
+; RV64I-NEXT:    slli a3, a3, 12
+; RV64I-NEXT:    addi a3, a3, 1365
+; RV64I-NEXT:    slli a3, a3, 12
+; RV64I-NEXT:    addi a3, a3, 1365
+; RV64I-NEXT:    and a0, a0, a3
+; RV64I-NEXT:    or a0, a1, a0
+; RV64I-NEXT:    slli a1, a0, 2
+; RV64I-NEXT:    lui a4, 1035469
+; RV64I-NEXT:    addiw a4, a4, -819
+; RV64I-NEXT:    slli a4, a4, 12
+; RV64I-NEXT:    addi a4, a4, -819
+; RV64I-NEXT:    slli a4, a4, 12
+; RV64I-NEXT:    addi a4, a4, -819
+; RV64I-NEXT:    slli a4, a4, 12
+; RV64I-NEXT:    addi a4, a4, -820
+; RV64I-NEXT:    and a1, a1, a4
+; RV64I-NEXT:    srli a0, a0, 2
+; RV64I-NEXT:    lui a5, 13107
+; RV64I-NEXT:    addiw a5, a5, 819
+; RV64I-NEXT:    slli a5, a5, 12
+; RV64I-NEXT:    addi a5, a5, 819
+; RV64I-NEXT:    slli a5, a5, 12
+; RV64I-NEXT:    addi a5, a5, 819
+; RV64I-NEXT:    slli a5, a5, 12
+; RV64I-NEXT:    addi a5, a5, 819
+; RV64I-NEXT:    and a0, a0, a5
+; RV64I-NEXT:    or a0, a1, a0
+; RV64I-NEXT:    slli a1, a0, 1
+; RV64I-NEXT:    and a1, a1, a2
+; RV64I-NEXT:    srli a0, a0, 1
+; RV64I-NEXT:    and a0, a0, a3
+; RV64I-NEXT:    or a0, a1, a0
+; RV64I-NEXT:    slli a1, a0, 2
+; RV64I-NEXT:    and a1, a1, a4
+; RV64I-NEXT:    srli a0, a0, 2
+; RV64I-NEXT:    and a0, a0, a5
+; RV64I-NEXT:    or a0, a1, a0
+; RV64I-NEXT:    ret
+;
+; RV64IB-LABEL: grev0_i64:
+; RV64IB:       # %bb.0:
+; RV64IB-NEXT:    ret
+;
+; RV64IBP-LABEL: grev0_i64:
+; RV64IBP:       # %bb.0:
+; RV64IBP-NEXT:    ret
+  %and1 = shl i64 %a, 1
+  %shl1 = and i64 %and1, -6148914691236517206
+  %and1b = lshr i64 %a, 1
+  %shr1 = and i64 %and1b, 6148914691236517205
+  %or1 = or i64 %shl1, %shr1
+  %and2 = shl i64 %or1, 2
+  %shl2 = and i64 %and2, -3689348814741910324
+  %and2b = lshr i64 %or1, 2
+  %shr2 = and i64 %and2b, 3689348814741910323
+  %or2 = or i64 %shl2, %shr2
+  %and3 = shl i64 %or2, 1
+  %shl3 = and i64 %and3, -6148914691236517206
+  %and3b = lshr i64 %or2, 1
+  %shr3 = and i64 %and3b, 6148914691236517205
+  %or3 = or i64 %shl3, %shr3
+  %and4 = shl i64 %or3, 2
+  %shl4 = and i64 %and4, -3689348814741910324
+  %and4b = lshr i64 %or3, 2
+  %shr4 = and i64 %and4b, 3689348814741910323
+  %or4 = or i64 %shl4, %shr4
+  ret i64 %or4
+}
+
 declare i64 @llvm.fshl.i64(i64, i64, i64)
 declare i64 @llvm.fshr.i64(i64, i64, i64)