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
@@ -8931,21 +8931,33 @@
   return UseMask(NewMask);
 }
 
-static void computeGREV(APInt &Src, unsigned ShAmt) {
+static void computeGREVOrGORC(APInt &Src, unsigned ShAmt, bool IsGORC,
+                              bool ComputeZeros = false) {
+  static const uint64_t GREVMasks[] = {
+      0x5555555555555555ULL, 0x3333333333333333ULL, 0x0F0F0F0F0F0F0F0FULL,
+      0x00FF00FF00FF00FFULL, 0x0000FFFF0000FFFFULL, 0x00000000FFFFFFFFULL};
+
   ShAmt &= Src.getBitWidth() - 1;
   uint64_t x = Src.getZExtValue();
-  if (ShAmt & 1)
-    x = ((x & 0x5555555555555555LL) << 1) | ((x & 0xAAAAAAAAAAAAAAAALL) >> 1);
-  if (ShAmt & 2)
-    x = ((x & 0x3333333333333333LL) << 2) | ((x & 0xCCCCCCCCCCCCCCCCLL) >> 2);
-  if (ShAmt & 4)
-    x = ((x & 0x0F0F0F0F0F0F0F0FLL) << 4) | ((x & 0xF0F0F0F0F0F0F0F0LL) >> 4);
-  if (ShAmt & 8)
-    x = ((x & 0x00FF00FF00FF00FFLL) << 8) | ((x & 0xFF00FF00FF00FF00LL) >> 8);
-  if (ShAmt & 16)
-    x = ((x & 0x0000FFFF0000FFFFLL) << 16) | ((x & 0xFFFF0000FFFF0000LL) >> 16);
-  if (ShAmt & 32)
-    x = ((x & 0x00000000FFFFFFFFLL) << 32) | ((x & 0xFFFFFFFF00000000LL) >> 32);
+
+  // To compute zeros, we need to invert the value and invert it back after.
+  if (ComputeZeros)
+    x = ~x;
+
+  for (unsigned Stage = 0; Stage != 6; ++Stage) {
+    unsigned Shift = 1 << Stage;
+    if (ShAmt & Shift) {
+      uint64_t Mask = GREVMasks[Stage];
+      uint64_t Res = ((x & Mask) << Shift) | ((x >> Shift) & Mask);
+      if (IsGORC)
+        Res |= x;
+      x = Res;
+    }
+  }
+
+  if (ComputeZeros)
+    x = ~x;
+
   Src = x;
 }
 
@@ -9011,12 +9023,15 @@
     Known.Zero.setBitsFrom(LowBits);
     break;
   }
-  case RISCVISD::GREV: {
+  case RISCVISD::GREV:
+  case RISCVISD::GORC: {
     if (auto *C = dyn_cast<ConstantSDNode>(Op.getOperand(1))) {
       Known = DAG.computeKnownBits(Op.getOperand(0), Depth + 1);
       unsigned ShAmt = C->getZExtValue();
-      computeGREV(Known.Zero, ShAmt);
-      computeGREV(Known.One, ShAmt);
+      bool IsGORC = Op.getOpcode() == RISCVISD::GORC;
+      computeGREVOrGORC(Known.Zero, ShAmt, IsGORC,
+                        /*ComputeZeros*/ true);
+      computeGREVOrGORC(Known.One, ShAmt, IsGORC);
     }
     break;
   }
diff --git a/llvm/test/CodeGen/RISCV/rv32zbb-intrinsic.ll b/llvm/test/CodeGen/RISCV/rv32zbb-intrinsic.ll
--- a/llvm/test/CodeGen/RISCV/rv32zbb-intrinsic.ll
+++ b/llvm/test/CodeGen/RISCV/rv32zbb-intrinsic.ll
@@ -12,3 +12,22 @@
   %tmp = call i32 @llvm.riscv.orc.b.i32(i32 %a)
   ret i32 %tmp
 }
+
+; Second and+or are redundant with the first, make sure we remove it.
+define i32 @orcb_knownbits(i32 %a) nounwind {
+; RV32ZBB-LABEL: orcb_knownbits:
+; RV32ZBB:       # %bb.0:
+; RV32ZBB-NEXT:    lui a1, 1044480
+; RV32ZBB-NEXT:    and a0, a0, a1
+; RV32ZBB-NEXT:    lui a1, 2048
+; RV32ZBB-NEXT:    addi a1, a1, 1
+; RV32ZBB-NEXT:    or a0, a0, a1
+; RV32ZBB-NEXT:    orc.b a0, a0
+; RV32ZBB-NEXT:    ret
+  %tmp = and i32 %a, 4278190080 ; 0xFF000000
+  %tmp2 = or i32 %tmp, 8388609 ; 0x800001
+  %tmp3 = call i32 @llvm.riscv.orc.b.i32(i32 %tmp2)
+  %tmp4 = and i32 %tmp3, 4278190080 ; 0xFF000000
+  %tmp5 = or i32 %tmp4, 16711935 ; 0xFF00FF
+  ret i32 %tmp5
+}
diff --git a/llvm/test/CodeGen/RISCV/rv64zbb-intrinsic.ll b/llvm/test/CodeGen/RISCV/rv64zbb-intrinsic.ll
--- a/llvm/test/CodeGen/RISCV/rv64zbb-intrinsic.ll
+++ b/llvm/test/CodeGen/RISCV/rv64zbb-intrinsic.ll
@@ -25,20 +25,46 @@
 ; RV64ZBB-LABEL: orcb32_zext:
 ; RV64ZBB:       # %bb.0:
 ; RV64ZBB-NEXT:    orc.b a0, a0
-; RV64ZBB-NEXT:    slli a0, a0, 32
-; RV64ZBB-NEXT:    srli a0, a0, 32
 ; RV64ZBB-NEXT:    ret
 ;
 ; RV64ZBP-LABEL: orcb32_zext:
 ; RV64ZBP:       # %bb.0:
 ; RV64ZBP-NEXT:    orc.b a0, a0
-; RV64ZBP-NEXT:    slli a0, a0, 32
-; RV64ZBP-NEXT:    srli a0, a0, 32
 ; RV64ZBP-NEXT:    ret
   %tmp = call i32 @llvm.riscv.orc.b.i32(i32 %a)
   ret i32 %tmp
 }
 
+; Second and+or is redundant with the first, make sure we remove them.
+define signext i32 @orcb32_knownbits(i32 signext %a) nounwind {
+; RV64ZBB-LABEL: orcb32_knownbits:
+; RV64ZBB:       # %bb.0:
+; RV64ZBB-NEXT:    lui a1, 1044480
+; RV64ZBB-NEXT:    and a0, a0, a1
+; RV64ZBB-NEXT:    lui a1, 2048
+; RV64ZBB-NEXT:    addiw a1, a1, 1
+; RV64ZBB-NEXT:    or a0, a0, a1
+; RV64ZBB-NEXT:    orc.b a0, a0
+; RV64ZBB-NEXT:    sext.w a0, a0
+; RV64ZBB-NEXT:    ret
+;
+; RV64ZBP-LABEL: orcb32_knownbits:
+; RV64ZBP:       # %bb.0:
+; RV64ZBP-NEXT:    lui a1, 1044480
+; RV64ZBP-NEXT:    and a0, a0, a1
+; RV64ZBP-NEXT:    lui a1, 2048
+; RV64ZBP-NEXT:    addiw a1, a1, 1
+; RV64ZBP-NEXT:    or a0, a0, a1
+; RV64ZBP-NEXT:    gorciw a0, a0, 7
+; RV64ZBP-NEXT:    ret
+  %tmp = and i32 %a, 4278190080 ; 0xFF000000
+  %tmp2 = or i32 %tmp, 8388609 ; 0x800001
+  %tmp3 = call i32 @llvm.riscv.orc.b.i32(i32 %tmp2)
+  %tmp4 = and i32 %tmp3, 4278190080 ; 0xFF000000
+  %tmp5 = or i32 %tmp4, 16711935 ; 0xFF00FF
+  ret i32 %tmp5
+}
+
 declare i64 @llvm.riscv.orc.b.i64(i64)
 
 define i64 @orcb64(i64 %a) nounwind {
@@ -54,3 +80,40 @@
   %tmp = call i64 @llvm.riscv.orc.b.i64(i64 %a)
   ret i64 %tmp
 }
+
+; Second and+or is redundant with the first, make sure we remove them.
+define i64 @orcb64_knownbits(i64 %a) nounwind {
+; RV64ZBB-LABEL: orcb64_knownbits:
+; RV64ZBB:       # %bb.0:
+; RV64ZBB-NEXT:    lui a1, 65535
+; RV64ZBB-NEXT:    slli a1, a1, 12
+; RV64ZBB-NEXT:    and a0, a0, a1
+; RV64ZBB-NEXT:    lui a1, 131073
+; RV64ZBB-NEXT:    slli a1, a1, 13
+; RV64ZBB-NEXT:    addi a1, a1, 1
+; RV64ZBB-NEXT:    slli a1, a1, 20
+; RV64ZBB-NEXT:    addi a1, a1, 8
+; RV64ZBB-NEXT:    or a0, a0, a1
+; RV64ZBB-NEXT:    orc.b a0, a0
+; RV64ZBB-NEXT:    ret
+;
+; RV64ZBP-LABEL: orcb64_knownbits:
+; RV64ZBP:       # %bb.0:
+; RV64ZBP-NEXT:    lui a1, 65535
+; RV64ZBP-NEXT:    slli a1, a1, 12
+; RV64ZBP-NEXT:    and a0, a0, a1
+; RV64ZBP-NEXT:    lui a1, 131073
+; RV64ZBP-NEXT:    slli a1, a1, 13
+; RV64ZBP-NEXT:    addi a1, a1, 1
+; RV64ZBP-NEXT:    slli a1, a1, 20
+; RV64ZBP-NEXT:    addi a1, a1, 8
+; RV64ZBP-NEXT:    or a0, a0, a1
+; RV64ZBP-NEXT:    orc.b a0, a0
+; RV64ZBP-NEXT:    ret
+  %tmp = and i64 %a, 1099494850560 ; 0x000000ffff000000
+  %tmp2 = or i64 %tmp, 4611721202800525320 ; 0x4000200000100008
+  %tmp3 = call i64 @llvm.riscv.orc.b.i64(i64 %tmp2)
+  %tmp4 = and i64 %tmp3, 1099494850560 ; 0x000000ffff000000
+  %tmp5 = or i64 %tmp4, 18374966855153418495 ; 0xff00ff0000ff00ff
+  ret i64 %tmp5
+}
diff --git a/llvm/test/CodeGen/RISCV/rv64zbp-intrinsic.ll b/llvm/test/CodeGen/RISCV/rv64zbp-intrinsic.ll
--- a/llvm/test/CodeGen/RISCV/rv64zbp-intrinsic.ll
+++ b/llvm/test/CodeGen/RISCV/rv64zbp-intrinsic.ll
@@ -75,6 +75,15 @@
   ret i32 %tmp
 }
 
+define zeroext i32 @gorci32_zext(i32 zeroext %a) nounwind {
+; RV64ZBP-LABEL: gorci32_zext:
+; RV64ZBP:       # %bb.0:
+; RV64ZBP-NEXT:    orc.w a0, a0
+; RV64ZBP-NEXT:    ret
+  %tmp = call i32 @llvm.riscv.gorc.i32(i32 %a, i32 31)
+  ret i32 %tmp
+}
+
 declare i32 @llvm.riscv.shfl.i32(i32 %a, i32 %b)
 
 define signext i32 @shfl32(i32 signext %a, i32 signext %b) nounwind {
@@ -515,6 +524,21 @@
   ret i64 %tmp
 }
 
+; The second OR is redundant with the first. Make sure we remove it.
+define i64 @gorci64_knownbits(i64 %a) nounwind {
+; RV64ZBP-LABEL: gorci64_knownbits:
+; RV64ZBP:       # %bb.0:
+; RV64ZBP-NEXT:    lui a1, %hi(.LCPI54_0)
+; RV64ZBP-NEXT:    ld a1, %lo(.LCPI54_0)(a1)
+; RV64ZBP-NEXT:    or a0, a0, a1
+; RV64ZBP-NEXT:    orc32 a0, a0
+; RV64ZBP-NEXT:    ret
+  %tmp = or i64 %a, 72624976668147840 ; 0x102040810204080
+  %tmp2 = call i64 @llvm.riscv.gorc.i64(i64 %tmp, i64 32)
+  %tmp3 = or i64 %tmp2, 1234624599046636680 ; 0x1122448811224488
+  ret i64 %tmp3
+}
+
 define i64 @orchi64(i64 %a) nounwind {
 ; RV64ZBP-LABEL: orchi64:
 ; RV64ZBP:       # %bb.0: