diff --git a/llvm/lib/Target/RISCV/RISCVISelLowering.h b/llvm/lib/Target/RISCV/RISCVISelLowering.h
--- a/llvm/lib/Target/RISCV/RISCVISelLowering.h
+++ b/llvm/lib/Target/RISCV/RISCVISelLowering.h
@@ -74,6 +74,8 @@
   bool isTruncateFree(EVT SrcVT, EVT DstVT) const override;
   bool isZExtFree(SDValue Val, EVT VT2) const override;
   bool isSExtCheaperThanZExt(EVT SrcVT, EVT DstVT) const override;
+  bool isCheapToSpeculateCttz() const override;
+  bool isCheapToSpeculateCtlz() const override;
   bool isFPImmLegal(const APFloat &Imm, EVT VT,
                     bool ForCodeSize) const override;
 
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
@@ -365,6 +365,14 @@
   return Subtarget.is64Bit() && SrcVT == MVT::i32 && DstVT == MVT::i64;
 }
 
+bool RISCVTargetLowering::isCheapToSpeculateCttz() const {
+  return Subtarget.hasStdExtZbb();
+}
+
+bool RISCVTargetLowering::isCheapToSpeculateCtlz() const {
+  return Subtarget.hasStdExtZbb();
+}
+
 bool RISCVTargetLowering::isFPImmLegal(const APFloat &Imm, EVT VT,
                                        bool ForCodeSize) const {
   if (VT == MVT::f32 && !Subtarget.hasStdExtF())
diff --git a/llvm/lib/Target/RISCV/RISCVInstrInfoB.td b/llvm/lib/Target/RISCV/RISCVInstrInfoB.td
--- a/llvm/lib/Target/RISCV/RISCVInstrInfoB.td
+++ b/llvm/lib/Target/RISCV/RISCVInstrInfoB.td
@@ -1055,8 +1055,13 @@
 let Predicates = [HasStdExtZbb, IsRV64] in {
 def : Pat<(add (ctlz (and GPR:$rs1, (i64 0xFFFFFFFF))), (i64 -32)),
           (CLZW GPR:$rs1)>;
-// We don't pattern-match CTZW here as it has the same pattern and result as
-// RV64 CTZ
+// computeKnownBits can't figure out that the and mask on the add result is
+// unnecessary so we need to pattern match it away.
+def : Pat<(and (add (ctlz (and GPR:$rs1, (i64 0xFFFFFFFF))), (i64 -32)),
+               (i64 0xFFFFFFFF)),
+          (CLZW GPR:$rs1)>;
+def : Pat<(cttz (or GPR:$rs1, (i64 0x100000000))),
+          (CTZW GPR:$rs1)>;
 def : Pat<(ctpop (and GPR:$rs1, (i64 0xFFFFFFFF))), (PCNTW GPR:$rs1)>;
 } // Predicates = [HasStdExtZbb, IsRV64]
 
diff --git a/llvm/test/CodeGen/RISCV/rv32Zbb.ll b/llvm/test/CodeGen/RISCV/rv32Zbb.ll
--- a/llvm/test/CodeGen/RISCV/rv32Zbb.ll
+++ b/llvm/test/CodeGen/RISCV/rv32Zbb.ll
@@ -362,22 +362,12 @@
 ;
 ; RV32IB-LABEL: ctlz_i32:
 ; RV32IB:       # %bb.0:
-; RV32IB-NEXT:    beqz a0, .LBB8_2
-; RV32IB-NEXT:  # %bb.1: # %cond.false
 ; RV32IB-NEXT:    clz a0, a0
 ; RV32IB-NEXT:    ret
-; RV32IB-NEXT:  .LBB8_2:
-; RV32IB-NEXT:    addi a0, zero, 32
-; RV32IB-NEXT:    ret
 ;
 ; RV32IBB-LABEL: ctlz_i32:
 ; RV32IBB:       # %bb.0:
-; RV32IBB-NEXT:    beqz a0, .LBB8_2
-; RV32IBB-NEXT:  # %bb.1: # %cond.false
 ; RV32IBB-NEXT:    clz a0, a0
-; RV32IBB-NEXT:    ret
-; RV32IBB-NEXT:  .LBB8_2:
-; RV32IBB-NEXT:    addi a0, zero, 32
 ; RV32IBB-NEXT:    ret
   %1 = call i32 @llvm.ctlz.i32(i32 %a, i1 false)
   ret i32 %1
@@ -545,22 +535,12 @@
 ;
 ; RV32IB-LABEL: cttz_i32:
 ; RV32IB:       # %bb.0:
-; RV32IB-NEXT:    beqz a0, .LBB10_2
-; RV32IB-NEXT:  # %bb.1: # %cond.false
 ; RV32IB-NEXT:    ctz a0, a0
 ; RV32IB-NEXT:    ret
-; RV32IB-NEXT:  .LBB10_2:
-; RV32IB-NEXT:    addi a0, zero, 32
-; RV32IB-NEXT:    ret
 ;
 ; RV32IBB-LABEL: cttz_i32:
 ; RV32IBB:       # %bb.0:
-; RV32IBB-NEXT:    beqz a0, .LBB10_2
-; RV32IBB-NEXT:  # %bb.1: # %cond.false
 ; RV32IBB-NEXT:    ctz a0, a0
-; RV32IBB-NEXT:    ret
-; RV32IBB-NEXT:  .LBB10_2:
-; RV32IBB-NEXT:    addi a0, zero, 32
 ; RV32IBB-NEXT:    ret
   %1 = call i32 @llvm.cttz.i32(i32 %a, i1 false)
   ret i32 %1
diff --git a/llvm/test/CodeGen/RISCV/rv64Zbb.ll b/llvm/test/CodeGen/RISCV/rv64Zbb.ll
--- a/llvm/test/CodeGen/RISCV/rv64Zbb.ll
+++ b/llvm/test/CodeGen/RISCV/rv64Zbb.ll
@@ -290,22 +290,12 @@
 ;
 ; RV64IB-LABEL: ctlz_i32:
 ; RV64IB:       # %bb.0:
-; RV64IB-NEXT:    beqz a0, .LBB9_2
-; RV64IB-NEXT:  # %bb.1: # %cond.false
 ; RV64IB-NEXT:    clzw a0, a0
 ; RV64IB-NEXT:    ret
-; RV64IB-NEXT:  .LBB9_2:
-; RV64IB-NEXT:    addi a0, zero, 32
-; RV64IB-NEXT:    ret
 ;
 ; RV64IBB-LABEL: ctlz_i32:
 ; RV64IBB:       # %bb.0:
-; RV64IBB-NEXT:    beqz a0, .LBB9_2
-; RV64IBB-NEXT:  # %bb.1: # %cond.false
 ; RV64IBB-NEXT:    clzw a0, a0
-; RV64IBB-NEXT:    ret
-; RV64IBB-NEXT:  .LBB9_2:
-; RV64IBB-NEXT:    addi a0, zero, 32
 ; RV64IBB-NEXT:    ret
   %1 = call i32 @llvm.ctlz.i32(i32 %a, i1 false)
   ret i32 %1
@@ -385,22 +375,12 @@
 ;
 ; RV64IB-LABEL: ctlz_i64:
 ; RV64IB:       # %bb.0:
-; RV64IB-NEXT:    beqz a0, .LBB10_2
-; RV64IB-NEXT:  # %bb.1: # %cond.false
 ; RV64IB-NEXT:    clz a0, a0
 ; RV64IB-NEXT:    ret
-; RV64IB-NEXT:  .LBB10_2:
-; RV64IB-NEXT:    addi a0, zero, 64
-; RV64IB-NEXT:    ret
 ;
 ; RV64IBB-LABEL: ctlz_i64:
 ; RV64IBB:       # %bb.0:
-; RV64IBB-NEXT:    beqz a0, .LBB10_2
-; RV64IBB-NEXT:  # %bb.1: # %cond.false
 ; RV64IBB-NEXT:    clz a0, a0
-; RV64IBB-NEXT:    ret
-; RV64IBB-NEXT:  .LBB10_2:
-; RV64IBB-NEXT:    addi a0, zero, 64
 ; RV64IBB-NEXT:    ret
   %1 = call i64 @llvm.ctlz.i64(i64 %a, i1 false)
   ret i64 %1
@@ -470,22 +450,12 @@
 ;
 ; RV64IB-LABEL: cttz_i32:
 ; RV64IB:       # %bb.0:
-; RV64IB-NEXT:    beqz a0, .LBB11_2
-; RV64IB-NEXT:  # %bb.1: # %cond.false
-; RV64IB-NEXT:    ctz a0, a0
-; RV64IB-NEXT:    ret
-; RV64IB-NEXT:  .LBB11_2:
-; RV64IB-NEXT:    addi a0, zero, 32
+; RV64IB-NEXT:    ctzw a0, a0
 ; RV64IB-NEXT:    ret
 ;
 ; RV64IBB-LABEL: cttz_i32:
 ; RV64IBB:       # %bb.0:
-; RV64IBB-NEXT:    beqz a0, .LBB11_2
-; RV64IBB-NEXT:  # %bb.1: # %cond.false
-; RV64IBB-NEXT:    ctz a0, a0
-; RV64IBB-NEXT:    ret
-; RV64IBB-NEXT:  .LBB11_2:
-; RV64IBB-NEXT:    addi a0, zero, 32
+; RV64IBB-NEXT:    ctzw a0, a0
 ; RV64IBB-NEXT:    ret
   %1 = call i32 @llvm.cttz.i32(i32 %a, i1 false)
   ret i32 %1
@@ -555,22 +525,12 @@
 ;
 ; RV64IB-LABEL: cttz_i64:
 ; RV64IB:       # %bb.0:
-; RV64IB-NEXT:    beqz a0, .LBB12_2
-; RV64IB-NEXT:  # %bb.1: # %cond.false
 ; RV64IB-NEXT:    ctz a0, a0
 ; RV64IB-NEXT:    ret
-; RV64IB-NEXT:  .LBB12_2:
-; RV64IB-NEXT:    addi a0, zero, 64
-; RV64IB-NEXT:    ret
 ;
 ; RV64IBB-LABEL: cttz_i64:
 ; RV64IBB:       # %bb.0:
-; RV64IBB-NEXT:    beqz a0, .LBB12_2
-; RV64IBB-NEXT:  # %bb.1: # %cond.false
 ; RV64IBB-NEXT:    ctz a0, a0
-; RV64IBB-NEXT:    ret
-; RV64IBB-NEXT:  .LBB12_2:
-; RV64IBB-NEXT:    addi a0, zero, 64
 ; RV64IBB-NEXT:    ret
   %1 = call i64 @llvm.cttz.i64(i64 %a, i1 false)
   ret i64 %1