diff --git a/llvm/lib/Target/RISCV/RISCVCodeGenPrepare.cpp b/llvm/lib/Target/RISCV/RISCVCodeGenPrepare.cpp
--- a/llvm/lib/Target/RISCV/RISCVCodeGenPrepare.cpp
+++ b/llvm/lib/Target/RISCV/RISCVCodeGenPrepare.cpp
@@ -29,6 +29,8 @@
 #define PASS_NAME "RISCV CodeGenPrepare"
 
 STATISTIC(NumZExtToSExt, "Number of SExt instructions converted to ZExt");
+STATISTIC(NumZExtToSExtNonNeg,
+          "Number of SExt non negative value instructions converted to ZExt");
 
 namespace {
 
@@ -83,7 +85,29 @@
     ++NumZExtToSExt;
     return true;
   }
+  // Look for a non negative zext(value) and replace it with sext.
+	if (isKnownNonNegative(Src, *DL)) {
+    auto SExt = new SExtInst(Src, ZExt.getType(), "", &ZExt);
+    SExt->takeName(&ZExt);
+    SExt->setDebugLoc(ZExt.getDebugLoc());
+
+    ZExt.replaceAllUsesWith(SExt);
+    ZExt.eraseFromParent();
+    ++NumZExtToSExtNonNeg;
+    return true;
+  }
 
+  // Look for zext instructions that have the nneg flag.
+  if (ZExt.hasNonNeg()){
+    auto SExt = new SExtInst(Src, ZExt.getType(), "", &ZExt);
+    SExt->takeName(&ZExt);
+    SExt->setDebugLoc(ZExt.getDebugLoc());
+
+    ZExt.replaceAllUsesWith(SExt);
+    ZExt.eraseFromParent();
+    ++NumZExtToSExtNonNeg;
+    return true; 
+  }
   // Convert (zext (abs(i32 X, i1 1))) -> (sext (abs(i32 X, i1 1))). If abs of
   // INT_MIN is poison, the sign bit is zero.
   using namespace PatternMatch;
diff --git a/llvm/test/CodeGen/RISCV/riscv-codegenprepare-asm.ll b/llvm/test/CodeGen/RISCV/riscv-codegenprepare-asm.ll
--- a/llvm/test/CodeGen/RISCV/riscv-codegenprepare-asm.ll
+++ b/llvm/test/CodeGen/RISCV/riscv-codegenprepare-asm.ll
@@ -125,3 +125,15 @@
   %niter.ncmp.1 = icmp eq i64 %niter.next.1, %unroll_iter
   br i1 %niter.ncmp.1, label %for.cond.cleanup.loopexit.unr-lcssa, label %for.body
 }
+
+define i64 @test3(i32 noundef %a){
+; CHECK-LABEL: test3:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    sext.w a0, a0
+; CHECK-NEXT:    addi a0, a0, 5
+; CHECK-NEXT:    ret
+
+  %ext = zext nneg i32 %a to i64
+  %added = add i64 %ext, 5
+  ret i64 %added
+}
diff --git a/llvm/test/CodeGen/RISCV/riscv-codegenprepare.ll b/llvm/test/CodeGen/RISCV/riscv-codegenprepare.ll
--- a/llvm/test/CodeGen/RISCV/riscv-codegenprepare.ll
+++ b/llvm/test/CodeGen/RISCV/riscv-codegenprepare.ll
@@ -142,3 +142,31 @@
   %niter.ncmp.1 = icmp eq i64 %niter.next.1, %unroll_iter
   br i1 %niter.ncmp.1, label %for.cond.cleanup.loopexit.unr-lcssa, label %for.body
 }
+
+declare void @llvm.assume(i1 %assume);
+define i64 @test3(i32 noundef signext %a){
+; CHECK-LABEL: @test3(
+; CHECK-NEXT:    [[ASSUME:%.*]] = icmp sge i32 [[A:%.*]], 0
+; CHECK-NEXT:    call void @llvm.assume(i1 [[ASSUME]])
+; CHECK-NEXT:    [[EXT:%.*]] = zext i32 [[A]] to i64
+; CHECK-NEXT:    ret i64 [[EXT]]
+;
+  %assume = icmp sge i32 %a, 0;
+  call void @llvm.assume(i1 %assume)
+  %ext = zext i32 %a to i64
+  ret i64 %ext
+}
+
+
+define i64 @test4(i32 noundef %a){
+; CHECK-LABEL: @test4(
+; CHECK-NEXT:    [[EXT:%.*]] = sext i32 [[A:%.*]] to i64
+; CHECK-NEXT:    [[ADDED:%.*]] = add i64 [[EXT]], 5
+; CHECK-NEXT:    ret i64 [[EXT]]
+;
+  %ext = zext nneg i32 %a to i64
+  %added = add i64 %ext, 5
+  ret i64 %ext;
+}
+
+