Index: lib/Transforms/Utils/SimplifyLibCalls.cpp
===================================================================
--- lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -22,6 +22,7 @@
 #include "llvm/Transforms/Utils/Local.h"
 #include "llvm/Analysis/ValueTracking.h"
 #include "llvm/Analysis/CaptureTracking.h"
+#include "llvm/Analysis/Loads.h"
 #include "llvm/IR/DataLayout.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/IRBuilder.h"
@@ -150,6 +151,17 @@
   return true;
 }
 
+static bool canTransformToMemCmp(CallInst *CI, Value *Str, uint64_t Len,
+                                 const DataLayout &DL) {
+  if (!isOnlyUsedInZeroEqualityComparison(CI))
+    return false;
+
+  if (!isDereferenceableAndAlignedPointer(Str, 1, APInt(64, Len), DL))
+    return false;
+    
+  return true;
+}
+
 //===----------------------------------------------------------------------===//
 // String and Memory Library Call Optimizations
 //===----------------------------------------------------------------------===//
@@ -322,6 +334,22 @@
                       B, DL, TLI);
   }
 
+  // strcmp to memcmp
+  uint64_t Len = 0;
+  if (!HasStr1 && !HasStr2) {
+    return nullptr;
+  } else if (!HasStr1 && HasStr2) {
+    Len = Len2;
+  } else if (HasStr1 && !HasStr2) {
+    std::swap(Str1P, Str2P);
+    Len = Len1;
+  }
+
+  if (canTransformToMemCmp(CI, Str1P, Len, DL))
+    return emitMemCmp(Str1P, Str2P,
+                      ConstantInt::get(DL.getIntPtrType(CI->getContext()), Len),
+                      B, DL, TLI);
+
   return nullptr;
 }
 
@@ -361,6 +389,16 @@
   if (HasStr2 && Str2.empty()) // strncmp(x, "", n) -> *x
     return B.CreateZExt(B.CreateLoad(Str1P, "strcmpload"), CI->getType());
 
+  // strncmp to memcmp
+  if (!HasStr1 && !HasStr2) {
+    return nullptr;
+  } else if (HasStr1 && !HasStr2) {
+    std::swap(Str1P, Str2P);
+  }
+
+  if (canTransformToMemCmp(CI, Str1P, Length, DL))
+    return emitMemCmp(Str1P, Str2P, CI->getArgOperand(2), B, DL, TLI);
+
   return nullptr;
 }
 
Index: test/Transforms/InstCombine/strcmp-memcmp.ll
===================================================================
--- test/Transforms/InstCombine/strcmp-memcmp.ll
+++ test/Transforms/InstCombine/strcmp-memcmp.ll
@@ -0,0 +1,550 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -instcombine -S | FileCheck %s
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+
+@key = constant [4 x i8] c"key\00", align 1
+
+declare void @use(i32)
+
+define i32 @strcmp_memcmp([12 x i8]* %buf) {
+; CHECK-LABEL: @strcmp_memcmp(
+; CHECK-NEXT:    [[STRING:%.*]] = getelementptr inbounds [12 x i8], [12 x i8]* [[BUF:%.*]], i64 0, i64 0
+; CHECK-NEXT:    call void @llvm.lifetime.start.p0i8(i64 12, i8* nonnull [[STRING]])
+; CHECK-NEXT:    [[CALL:%.*]] = call i32 @strcmp(i8* nonnull [[STRING]], i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0))
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i32 [[CALL]], 0
+; CHECK-NEXT:    [[CONV:%.*]] = zext i1 [[CMP]] to i32
+; CHECK-NEXT:    call void @llvm.lifetime.end.p0i8(i64 12, i8* nonnull [[STRING]])
+; CHECK-NEXT:    ret i32 [[CONV]]
+;
+  %string = getelementptr inbounds [12 x i8], [12 x i8]* %buf, i64 0, i64 0
+  call void @llvm.lifetime.start.p0i8(i64 12, i8* nonnull %string)
+  %call = call i32 @strcmp(i8* nonnull %string, i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0))
+  %cmp = icmp eq i32 %call, 0
+  %conv = zext i1 %cmp to i32
+  call void @llvm.lifetime.end.p0i8(i64 12, i8* nonnull %string)
+  ret i32 %conv
+}
+
+declare void @llvm.lifetime.start.p0i8(i64, i8* nocapture)
+declare i32 @strcmp(i8* nocapture, i8* nocapture)
+declare void @llvm.lifetime.end.p0i8(i64, i8* nocapture)
+
+define i32 @strcmp_memcmp2([12 x i8]* %buf) {
+; CHECK-LABEL: @strcmp_memcmp2(
+; CHECK-NEXT:    [[STRING:%.*]] = getelementptr inbounds [12 x i8], [12 x i8]* [[BUF:%.*]], i64 0, i64 0
+; CHECK-NEXT:    call void @llvm.lifetime.start.p0i8(i64 12, i8* nonnull [[STRING]])
+; CHECK-NEXT:    [[CALL:%.*]] = call i32 @strcmp(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0), i8* nonnull [[STRING]])
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i32 [[CALL]], 0
+; CHECK-NEXT:    [[CONV:%.*]] = zext i1 [[CMP]] to i32
+; CHECK-NEXT:    call void @llvm.lifetime.end.p0i8(i64 12, i8* nonnull [[STRING]])
+; CHECK-NEXT:    ret i32 [[CONV]]
+;
+  %string = getelementptr inbounds [12 x i8], [12 x i8]* %buf, i64 0, i64 0
+  call void @llvm.lifetime.start.p0i8(i64 12, i8* nonnull %string)
+  %call = call i32 @strcmp(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0), i8* nonnull %string)
+  %cmp = icmp eq i32 %call, 0
+  %conv = zext i1 %cmp to i32
+  call void @llvm.lifetime.end.p0i8(i64 12, i8* nonnull %string)
+  ret i32 %conv
+}
+
+define i32 @strcmp_memcmp3([12 x i8]* %buf) {
+; CHECK-LABEL: @strcmp_memcmp3(
+; CHECK-NEXT:    [[STRING:%.*]] = getelementptr inbounds [12 x i8], [12 x i8]* [[BUF:%.*]], i64 0, i64 0
+; CHECK-NEXT:    call void @llvm.lifetime.start.p0i8(i64 12, i8* nonnull [[STRING]])
+; CHECK-NEXT:    [[CALL:%.*]] = call i32 @strcmp(i8* nonnull [[STRING]], i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0))
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ne i32 [[CALL]], 0
+; CHECK-NEXT:    [[CONV:%.*]] = zext i1 [[CMP]] to i32
+; CHECK-NEXT:    call void @llvm.lifetime.end.p0i8(i64 12, i8* nonnull [[STRING]])
+; CHECK-NEXT:    ret i32 [[CONV]]
+;
+  %string = getelementptr inbounds [12 x i8], [12 x i8]* %buf, i64 0, i64 0
+  call void @llvm.lifetime.start.p0i8(i64 12, i8* nonnull %string)
+  %call = call i32 @strcmp(i8* nonnull %string, i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0))
+  %cmp = icmp ne i32 %call, 0
+  %conv = zext i1 %cmp to i32
+  call void @llvm.lifetime.end.p0i8(i64 12, i8* nonnull %string)
+  ret i32 %conv
+}
+
+define i32 @strcmp_memcmp4([12 x i8]* %buf) {
+; CHECK-LABEL: @strcmp_memcmp4(
+; CHECK-NEXT:    [[STRING:%.*]] = getelementptr inbounds [12 x i8], [12 x i8]* [[BUF:%.*]], i64 0, i64 0
+; CHECK-NEXT:    call void @llvm.lifetime.start.p0i8(i64 12, i8* nonnull [[STRING]])
+; CHECK-NEXT:    [[CALL:%.*]] = call i32 @strcmp(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0), i8* nonnull [[STRING]])
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ne i32 [[CALL]], 0
+; CHECK-NEXT:    [[CONV:%.*]] = zext i1 [[CMP]] to i32
+; CHECK-NEXT:    call void @llvm.lifetime.end.p0i8(i64 12, i8* nonnull [[STRING]])
+; CHECK-NEXT:    ret i32 [[CONV]]
+;
+  %string = getelementptr inbounds [12 x i8], [12 x i8]* %buf, i64 0, i64 0
+  call void @llvm.lifetime.start.p0i8(i64 12, i8* nonnull %string)
+  %call = call i32 @strcmp(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0), i8* nonnull %string)
+  %cmp = icmp ne i32 %call, 0
+  %conv = zext i1 %cmp to i32
+  call void @llvm.lifetime.end.p0i8(i64 12, i8* nonnull %string)
+  ret i32 %conv
+}
+
+define i32 @strcmp_memcmp5([5 x i8]* %buf) {
+; CHECK-LABEL: @strcmp_memcmp5(
+; CHECK-NEXT:    [[STRING:%.*]] = getelementptr inbounds [5 x i8], [5 x i8]* [[BUF:%.*]], i64 0, i64 0
+; CHECK-NEXT:    call void @llvm.lifetime.start.p0i8(i64 5, i8* nonnull [[STRING]])
+; CHECK-NEXT:    [[CALL:%.*]] = call i32 @strcmp(i8* nonnull align 1 [[STRING]], i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0))
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i32 [[CALL]], 0
+; CHECK-NEXT:    [[CONV:%.*]] = zext i1 [[CMP]] to i32
+; CHECK-NEXT:    call void @llvm.lifetime.end.p0i8(i64 5, i8* nonnull [[STRING]])
+; CHECK-NEXT:    ret i32 [[CONV]]
+;
+  %string = getelementptr inbounds [5 x i8], [5 x i8]* %buf, i64 0, i64 0
+  call void @llvm.lifetime.start.p0i8(i64 5, i8* nonnull %string)
+  %call = call i32 @strcmp(i8* nonnull align 1 %string, i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0))
+  %cmp = icmp eq i32 %call, 0
+  %conv = zext i1 %cmp to i32
+  call void @llvm.lifetime.end.p0i8(i64 5, i8* nonnull %string)
+  ret i32 %conv
+}
+
+define i32 @strncmp_memcmp([12 x i8]* %buf) {
+; CHECK-LABEL: @strncmp_memcmp(
+; CHECK-NEXT:    [[STRING:%.*]] = getelementptr inbounds [12 x i8], [12 x i8]* [[BUF:%.*]], i64 0, i64 0
+; CHECK-NEXT:    call void @llvm.lifetime.start.p0i8(i64 12, i8* nonnull [[STRING]])
+; CHECK-NEXT:    [[CALL:%.*]] = call i32 @strncmp(i8* nonnull [[STRING]], i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0), i64 2)
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i32 [[CALL]], 0
+; CHECK-NEXT:    [[CONV:%.*]] = zext i1 [[CMP]] to i32
+; CHECK-NEXT:    call void @llvm.lifetime.end.p0i8(i64 12, i8* nonnull [[STRING]])
+; CHECK-NEXT:    ret i32 [[CONV]]
+;
+  %string = getelementptr inbounds [12 x i8], [12 x i8]* %buf, i64 0, i64 0
+  call void @llvm.lifetime.start.p0i8(i64 12, i8* nonnull %string)
+  %call = call i32 @strncmp(i8* nonnull %string, i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0), i64 2)
+  %cmp = icmp eq i32 %call, 0
+  %conv = zext i1 %cmp to i32
+  call void @llvm.lifetime.end.p0i8(i64 12, i8* nonnull %string)
+  ret i32 %conv
+}
+
+declare i32 @strncmp(i8* nocapture, i8* nocapture, i64)
+
+define i32 @strncmp_memcmp2([12 x i8]* %buf) {
+; CHECK-LABEL: @strncmp_memcmp2(
+; CHECK-NEXT:    [[STRING:%.*]] = getelementptr inbounds [12 x i8], [12 x i8]* [[BUF:%.*]], i64 0, i64 0
+; CHECK-NEXT:    call void @llvm.lifetime.start.p0i8(i64 12, i8* nonnull [[STRING]])
+; CHECK-NEXT:    [[CALL:%.*]] = call i32 @strncmp(i8* nonnull [[STRING]], i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0), i64 11)
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ne i32 [[CALL]], 0
+; CHECK-NEXT:    [[CONV:%.*]] = zext i1 [[CMP]] to i32
+; CHECK-NEXT:    call void @llvm.lifetime.end.p0i8(i64 12, i8* nonnull [[STRING]])
+; CHECK-NEXT:    ret i32 [[CONV]]
+;
+  %string = getelementptr inbounds [12 x i8], [12 x i8]* %buf, i64 0, i64 0
+  call void @llvm.lifetime.start.p0i8(i64 12, i8* nonnull %string)
+  %call = call i32 @strncmp(i8* nonnull %string, i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0), i64 11)
+  %cmp = icmp ne i32 %call, 0
+  %conv = zext i1 %cmp to i32
+  call void @llvm.lifetime.end.p0i8(i64 12, i8* nonnull %string)
+  ret i32 %conv
+}
+
+define i32 @strncmp_memcmp3([12 x i8]* %buf) {
+; CHECK-LABEL: @strncmp_memcmp3(
+; CHECK-NEXT:    [[STRING:%.*]] = getelementptr inbounds [12 x i8], [12 x i8]* [[BUF:%.*]], i64 0, i64 0
+; CHECK-NEXT:    call void @llvm.lifetime.start.p0i8(i64 12, i8* nonnull [[STRING]])
+; CHECK-NEXT:    [[CALL:%.*]] = call i32 @strncmp(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0), i8* nonnull [[STRING]], i64 11)
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i32 [[CALL]], 0
+; CHECK-NEXT:    [[CONV:%.*]] = zext i1 [[CMP]] to i32
+; CHECK-NEXT:    call void @llvm.lifetime.end.p0i8(i64 12, i8* nonnull [[STRING]])
+; CHECK-NEXT:    ret i32 [[CONV]]
+;
+  %string = getelementptr inbounds [12 x i8], [12 x i8]* %buf, i64 0, i64 0
+  call void @llvm.lifetime.start.p0i8(i64 12, i8* nonnull %string)
+  %call = call i32 @strncmp(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0), i8* nonnull %string, i64 11)
+  %cmp = icmp eq i32 %call, 0
+  %conv = zext i1 %cmp to i32
+  call void @llvm.lifetime.end.p0i8(i64 12, i8* nonnull %string)
+  ret i32 %conv
+}
+
+define i32 @strncmp_memcmp4([12 x i8]* %buf) {
+; CHECK-LABEL: @strncmp_memcmp4(
+; CHECK-NEXT:    [[STRING:%.*]] = getelementptr inbounds [12 x i8], [12 x i8]* [[BUF:%.*]], i64 0, i64 0
+; CHECK-NEXT:    call void @llvm.lifetime.start.p0i8(i64 12, i8* nonnull [[STRING]])
+; CHECK-NEXT:    [[CALL:%.*]] = call i32 @strncmp(i8* nonnull [[STRING]], i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0), i64 5)
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i32 [[CALL]], 0
+; CHECK-NEXT:    [[CONV:%.*]] = zext i1 [[CMP]] to i32
+; CHECK-NEXT:    call void @llvm.lifetime.end.p0i8(i64 12, i8* nonnull [[STRING]])
+; CHECK-NEXT:    ret i32 [[CONV]]
+;
+  %string = getelementptr inbounds [12 x i8], [12 x i8]* %buf, i64 0, i64 0
+  call void @llvm.lifetime.start.p0i8(i64 12, i8* nonnull %string)
+  %call = call i32 @strncmp(i8* nonnull %string, i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0), i64 5)
+  %cmp = icmp eq i32 %call, 0
+  %conv = zext i1 %cmp to i32
+  call void @llvm.lifetime.end.p0i8(i64 12, i8* nonnull %string)
+  ret i32 %conv
+}
+
+define i32 @strncmp_memcmp5([12 x i8]* %buf) {
+; CHECK-LABEL: @strncmp_memcmp5(
+; CHECK-NEXT:    [[STRING:%.*]] = getelementptr inbounds [12 x i8], [12 x i8]* [[BUF:%.*]], i64 0, i64 0
+; CHECK-NEXT:    call void @llvm.lifetime.start.p0i8(i64 12, i8* nonnull [[STRING]])
+; CHECK-NEXT:    [[CALL:%.*]] = call i32 @strncmp(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0), i8* nonnull [[STRING]], i64 5)
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i32 [[CALL]], 0
+; CHECK-NEXT:    [[CONV:%.*]] = zext i1 [[CMP]] to i32
+; CHECK-NEXT:    call void @llvm.lifetime.end.p0i8(i64 12, i8* nonnull [[STRING]])
+; CHECK-NEXT:    ret i32 [[CONV]]
+;
+  %string = getelementptr inbounds [12 x i8], [12 x i8]* %buf, i64 0, i64 0
+  call void @llvm.lifetime.start.p0i8(i64 12, i8* nonnull %string)
+  %call = call i32 @strncmp(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0), i8* nonnull %string, i64 5)
+  %cmp = icmp eq i32 %call, 0
+  %conv = zext i1 %cmp to i32
+  call void @llvm.lifetime.end.p0i8(i64 12, i8* nonnull %string)
+  ret i32 %conv
+}
+
+
+define i32 @strncmp_memcmp6([12 x i8]* %buf) {
+; CHECK-LABEL: @strncmp_memcmp6(
+; CHECK-NEXT:    [[STRING:%.*]] = getelementptr inbounds [12 x i8], [12 x i8]* [[BUF:%.*]], i64 0, i64 0
+; CHECK-NEXT:    call void @llvm.lifetime.start.p0i8(i64 12, i8* nonnull [[STRING]])
+; CHECK-NEXT:    [[CALL:%.*]] = call i32 @strncmp(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0), i8* nonnull [[STRING]], i64 5)
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ne i32 [[CALL]], 0
+; CHECK-NEXT:    [[CONV:%.*]] = zext i1 [[CMP]] to i32
+; CHECK-NEXT:    call void @llvm.lifetime.end.p0i8(i64 12, i8* nonnull [[STRING]])
+; CHECK-NEXT:    ret i32 [[CONV]]
+;
+  %string = getelementptr inbounds [12 x i8], [12 x i8]* %buf, i64 0, i64 0
+  call void @llvm.lifetime.start.p0i8(i64 12, i8* nonnull %string)
+  %call = call i32 @strncmp(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0), i8* nonnull %string, i64 5)
+  %cmp = icmp ne i32 %call, 0
+  %conv = zext i1 %cmp to i32
+  call void @llvm.lifetime.end.p0i8(i64 12, i8* nonnull %string)
+  ret i32 %conv
+}
+
+define i32 @strncmp_memcmp7([12 x i8]* %buf) {
+; CHECK-LABEL: @strncmp_memcmp7(
+; CHECK-NEXT:    [[STRING:%.*]] = getelementptr inbounds [12 x i8], [12 x i8]* [[BUF:%.*]], i64 0, i64 0
+; CHECK-NEXT:    call void @llvm.lifetime.start.p0i8(i64 12, i8* nonnull [[STRING]])
+; CHECK-NEXT:    [[CALL:%.*]] = call i32 @strncmp(i8* nonnull [[STRING]], i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0), i64 4)
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i32 [[CALL]], 0
+; CHECK-NEXT:    [[CONV:%.*]] = zext i1 [[CMP]] to i32
+; CHECK-NEXT:    call void @llvm.lifetime.end.p0i8(i64 12, i8* nonnull [[STRING]])
+; CHECK-NEXT:    ret i32 [[CONV]]
+;
+  %string = getelementptr inbounds [12 x i8], [12 x i8]* %buf, i64 0, i64 0
+  call void @llvm.lifetime.start.p0i8(i64 12, i8* nonnull %string)
+  %call = call i32 @strncmp(i8* nonnull %string, i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0), i64 4)
+  %cmp = icmp eq i32 %call, 0
+  %conv = zext i1 %cmp to i32
+  call void @llvm.lifetime.end.p0i8(i64 12, i8* nonnull %string)
+  ret i32 %conv
+}
+
+define i32 @strncmp_memcmp8([12 x i8]* %buf) {
+; CHECK-LABEL: @strncmp_memcmp8(
+; CHECK-NEXT:    [[STRING:%.*]] = getelementptr inbounds [12 x i8], [12 x i8]* [[BUF:%.*]], i64 0, i64 0
+; CHECK-NEXT:    call void @llvm.lifetime.start.p0i8(i64 12, i8* nonnull [[STRING]])
+; CHECK-NEXT:    [[CALL:%.*]] = call i32 @strncmp(i8* nonnull [[STRING]], i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0), i64 3)
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i32 [[CALL]], 0
+; CHECK-NEXT:    [[CONV:%.*]] = zext i1 [[CMP]] to i32
+; CHECK-NEXT:    call void @llvm.lifetime.end.p0i8(i64 12, i8* nonnull [[STRING]])
+; CHECK-NEXT:    ret i32 [[CONV]]
+;
+  %string = getelementptr inbounds [12 x i8], [12 x i8]* %buf, i64 0, i64 0
+  call void @llvm.lifetime.start.p0i8(i64 12, i8* nonnull %string)
+  %call = call i32 @strncmp(i8* nonnull %string, i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0), i64 3)
+  %cmp = icmp eq i32 %call, 0
+  %conv = zext i1 %cmp to i32
+  call void @llvm.lifetime.end.p0i8(i64 12, i8* nonnull %string)
+  ret i32 %conv
+}
+
+; Negative tests
+define i32 @strcmp_memcmp_bad([12 x i8]* %buf) {
+; CHECK-LABEL: @strcmp_memcmp_bad(
+; CHECK-NEXT:    [[STRING:%.*]] = getelementptr inbounds [12 x i8], [12 x i8]* [[BUF:%.*]], i64 0, i64 0
+; CHECK-NEXT:    call void @llvm.lifetime.start.p0i8(i64 12, i8* nonnull [[STRING]])
+; CHECK-NEXT:    [[CALL:%.*]] = call i32 @strcmp(i8* nonnull [[STRING]], i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0))
+; CHECK-NEXT:    [[CMP:%.*]] = icmp sgt i32 [[CALL]], 0
+; CHECK-NEXT:    [[CONV:%.*]] = zext i1 [[CMP]] to i32
+; CHECK-NEXT:    call void @llvm.lifetime.end.p0i8(i64 12, i8* nonnull [[STRING]])
+; CHECK-NEXT:    ret i32 [[CONV]]
+;
+  %string = getelementptr inbounds [12 x i8], [12 x i8]* %buf, i64 0, i64 0
+  call void @llvm.lifetime.start.p0i8(i64 12, i8* nonnull %string)
+  %call = call i32 @strcmp(i8* nonnull %string, i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0))
+  %cmp = icmp sgt i32 %call, 0
+  %conv = zext i1 %cmp to i32
+  call void @llvm.lifetime.end.p0i8(i64 12, i8* nonnull %string)
+  ret i32 %conv
+}
+
+define i32 @strcmp_memcmp_bad2([12 x i8]* %buf) {
+; CHECK-LABEL: @strcmp_memcmp_bad2(
+; CHECK-NEXT:    [[STRING:%.*]] = getelementptr inbounds [12 x i8], [12 x i8]* [[BUF:%.*]], i64 0, i64 0
+; CHECK-NEXT:    call void @llvm.lifetime.start.p0i8(i64 12, i8* nonnull [[STRING]])
+; CHECK-NEXT:    [[CALL:%.*]] = call i32 @strcmp(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0), i8* nonnull [[STRING]])
+; CHECK-NEXT:    [[CMP:%.*]] = icmp slt i32 [[CALL]], 1
+; CHECK-NEXT:    [[CONV:%.*]] = zext i1 [[CMP]] to i32
+; CHECK-NEXT:    call void @llvm.lifetime.end.p0i8(i64 12, i8* nonnull [[STRING]])
+; CHECK-NEXT:    ret i32 [[CONV]]
+;
+  %string = getelementptr inbounds [12 x i8], [12 x i8]* %buf, i64 0, i64 0
+  call void @llvm.lifetime.start.p0i8(i64 12, i8* nonnull %string)
+  %call = call i32 @strcmp(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0), i8* nonnull %string)
+  %cmp = icmp slt i32 %call, 1
+  %conv = zext i1 %cmp to i32
+  call void @llvm.lifetime.end.p0i8(i64 12, i8* nonnull %string)
+  ret i32 %conv
+}
+
+define i32 @strcmp_memcmp_bad3([12 x i8]* %buf) {
+; CHECK-LABEL: @strcmp_memcmp_bad3(
+; CHECK-NEXT:    [[STRING:%.*]] = getelementptr inbounds [12 x i8], [12 x i8]* [[BUF:%.*]], i64 0, i64 0
+; CHECK-NEXT:    call void @llvm.lifetime.start.p0i8(i64 12, i8* nonnull [[STRING]])
+; CHECK-NEXT:    [[CALL:%.*]] = call i32 @strcmp(i8* nonnull [[STRING]], i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0))
+; CHECK-NEXT:    call void @llvm.lifetime.end.p0i8(i64 12, i8* nonnull [[STRING]])
+; CHECK-NEXT:    ret i32 [[CALL]]
+;
+  %string = getelementptr inbounds [12 x i8], [12 x i8]* %buf, i64 0, i64 0
+  call void @llvm.lifetime.start.p0i8(i64 12, i8* nonnull %string)
+  %call = call i32 @strcmp(i8* nonnull %string, i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0))
+  call void @llvm.lifetime.end.p0i8(i64 12, i8* nonnull %string)
+  ret i32 %call
+}
+
+
+define i32 @strcmp_memcmp_bad4(i8* nocapture readonly %buf) {
+; CHECK-LABEL: @strcmp_memcmp_bad4(
+; CHECK-NEXT:    [[CALL:%.*]] = tail call i32 @strcmp(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0), i8* [[BUF:%.*]])
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i32 [[CALL]], 0
+; CHECK-NEXT:    [[CONV:%.*]] = zext i1 [[CMP]] to i32
+; CHECK-NEXT:    ret i32 [[CONV]]
+;
+  %call = tail call i32 @strcmp(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0), i8* %buf)
+  %cmp = icmp eq i32 %call, 0
+  %conv = zext i1 %cmp to i32
+  ret i32 %conv
+}
+
+
+define i32 @strcmp_memcmp_bad5([3 x i8]* %buf) {
+; CHECK-LABEL: @strcmp_memcmp_bad5(
+; CHECK-NEXT:    [[STRING:%.*]] = getelementptr inbounds [3 x i8], [3 x i8]* [[BUF:%.*]], i64 0, i64 0
+; CHECK-NEXT:    call void @llvm.lifetime.start.p0i8(i64 3, i8* nonnull [[STRING]])
+; CHECK-NEXT:    [[CALL:%.*]] = call i32 @strcmp(i8* nonnull [[STRING]], i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0))
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i32 [[CALL]], 0
+; CHECK-NEXT:    [[CONV:%.*]] = zext i1 [[CMP]] to i32
+; CHECK-NEXT:    call void @llvm.lifetime.end.p0i8(i64 3, i8* nonnull [[STRING]])
+; CHECK-NEXT:    ret i32 [[CONV]]
+;
+  %string = getelementptr inbounds [3 x i8], [3 x i8]* %buf, i64 0, i64 0
+  call void @llvm.lifetime.start.p0i8(i64 3, i8* nonnull %string)
+  %call = call i32 @strcmp(i8* nonnull %string, i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0))
+  %cmp = icmp eq i32 %call, 0
+  %conv = zext i1 %cmp to i32
+  call void @llvm.lifetime.end.p0i8(i64 3, i8* nonnull %string)
+  ret i32 %conv
+}
+
+
+define i32 @strcmp_memcmp_bad6([4 x i8]* %buf) {
+; CHECK-LABEL: @strcmp_memcmp_bad6(
+; CHECK-NEXT:    [[STRING:%.*]] = getelementptr inbounds [4 x i8], [4 x i8]* [[BUF:%.*]], i64 0, i64 0
+; CHECK-NEXT:    call void @llvm.lifetime.start.p0i8(i64 4, i8* nonnull [[STRING]])
+; CHECK-NEXT:    [[CALL:%.*]] = call i32 @strcmp(i8* nonnull [[STRING]], i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0))
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i32 [[CALL]], 0
+; CHECK-NEXT:    [[CONV:%.*]] = zext i1 [[CMP]] to i32
+; CHECK-NEXT:    call void @llvm.lifetime.end.p0i8(i64 4, i8* nonnull [[STRING]])
+; CHECK-NEXT:    ret i32 [[CONV]]
+;
+  %string = getelementptr inbounds [4 x i8], [4 x i8]* %buf, i64 0, i64 0
+  call void @llvm.lifetime.start.p0i8(i64 4, i8* nonnull %string)
+  %call = call i32 @strcmp(i8* nonnull %string, i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0))
+  %cmp = icmp eq i32 %call, 0
+  %conv = zext i1 %cmp to i32
+  call void @llvm.lifetime.end.p0i8(i64 4, i8* nonnull %string)
+  ret i32 %conv
+}
+
+
+define i32 @strcmp_memcmp_bad7([4 x i8]* %buf, i8* nocapture readonly %k) {
+; CHECK-LABEL: @strcmp_memcmp_bad7(
+; CHECK-NEXT:    [[STRING:%.*]] = getelementptr inbounds [4 x i8], [4 x i8]* [[BUF:%.*]], i64 0, i64 0
+; CHECK-NEXT:    call void @llvm.lifetime.start.p0i8(i64 4, i8* nonnull [[STRING]])
+; CHECK-NEXT:    [[CALL:%.*]] = call i32 @strcmp(i8* nonnull [[STRING]], i8* [[K:%.*]])
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i32 [[CALL]], 0
+; CHECK-NEXT:    [[CONV:%.*]] = zext i1 [[CMP]] to i32
+; CHECK-NEXT:    call void @llvm.lifetime.end.p0i8(i64 4, i8* nonnull [[STRING]])
+; CHECK-NEXT:    ret i32 [[CONV]]
+;
+  %string = getelementptr inbounds [4 x i8], [4 x i8]* %buf, i64 0, i64 0
+  call void @llvm.lifetime.start.p0i8(i64 4, i8* nonnull %string)
+  %call = call i32 @strcmp(i8* nonnull %string, i8* %k)
+  %cmp = icmp eq i32 %call, 0
+  %conv = zext i1 %cmp to i32
+  call void @llvm.lifetime.end.p0i8(i64 4, i8* nonnull %string)
+  ret i32 %conv
+}
+
+define i32 @strcmp_memcmp_bad8(i8* nocapture readonly %k) {
+; CHECK-LABEL: @strcmp_memcmp_bad8(
+; CHECK-NEXT:    [[CALL:%.*]] = tail call i32 @strcmp(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0), i8* [[K:%.*]])
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i32 [[CALL]], 0
+; CHECK-NEXT:    [[CONV:%.*]] = zext i1 [[CMP]] to i32
+; CHECK-NEXT:    ret i32 [[CONV]]
+;
+  %call = tail call i32 @strcmp(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0), i8* %k)
+  %cmp = icmp eq i32 %call, 0
+  %conv = zext i1 %cmp to i32
+  ret i32 %conv
+}
+
+define i32 @strcmp_memcmp_bad9([4 x i8]* %buf) {
+; CHECK-LABEL: @strcmp_memcmp_bad9(
+; CHECK-NEXT:    [[STRING:%.*]] = getelementptr inbounds [4 x i8], [4 x i8]* [[BUF:%.*]], i64 0, i64 0
+; CHECK-NEXT:    call void @llvm.lifetime.start.p0i8(i64 4, i8* nonnull [[STRING]])
+; CHECK-NEXT:    [[CALL:%.*]] = call i32 @strcmp(i8* nonnull [[STRING]], i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0))
+; CHECK-NEXT:    tail call void @use(i32 [[CALL]])
+; CHECK-NEXT:    call void @llvm.lifetime.end.p0i8(i64 4, i8* nonnull [[STRING]])
+; CHECK-NEXT:    ret i32 0
+;
+  %string = getelementptr inbounds [4 x i8], [4 x i8]* %buf, i64 0, i64 0
+  call void @llvm.lifetime.start.p0i8(i64 4, i8* nonnull %string)
+  %call = call i32 @strcmp(i8* nonnull %string, i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0))
+  tail call void @use(i32 %call)
+  call void @llvm.lifetime.end.p0i8(i64 4, i8* nonnull %string)
+  ret i32 0
+}
+
+define i32 @strncmp_memcmp_bad([12 x i8]* %buf) {
+; CHECK-LABEL: @strncmp_memcmp_bad(
+; CHECK-NEXT:    [[STRING:%.*]] = getelementptr inbounds [12 x i8], [12 x i8]* [[BUF:%.*]], i64 0, i64 0
+; CHECK-NEXT:    call void @llvm.lifetime.start.p0i8(i64 12, i8* nonnull [[STRING]])
+; CHECK-NEXT:    [[CALL:%.*]] = call i32 @strncmp(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0), i8* nonnull [[STRING]], i64 5)
+; CHECK-NEXT:    [[CMP:%.*]] = icmp sgt i32 [[CALL]], 0
+; CHECK-NEXT:    [[CONV:%.*]] = zext i1 [[CMP]] to i32
+; CHECK-NEXT:    call void @llvm.lifetime.end.p0i8(i64 12, i8* nonnull [[STRING]])
+; CHECK-NEXT:    ret i32 [[CONV]]
+;
+  %string = getelementptr inbounds [12 x i8], [12 x i8]* %buf, i64 0, i64 0
+  call void @llvm.lifetime.start.p0i8(i64 12, i8* nonnull %string)
+  %call = call i32 @strncmp(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0), i8* nonnull %string, i64 5)
+  %cmp = icmp sgt i32 %call, 0
+  %conv = zext i1 %cmp to i32
+  call void @llvm.lifetime.end.p0i8(i64 12, i8* nonnull %string)
+  ret i32 %conv
+}
+
+
+define i32 @strncmp_memcmp_bad1([12 x i8]* %buf) {
+; CHECK-LABEL: @strncmp_memcmp_bad1(
+; CHECK-NEXT:    [[STRING:%.*]] = getelementptr inbounds [12 x i8], [12 x i8]* [[BUF:%.*]], i64 0, i64 0
+; CHECK-NEXT:    call void @llvm.lifetime.start.p0i8(i64 12, i8* nonnull [[STRING]])
+; CHECK-NEXT:    [[CALL:%.*]] = call i32 @strncmp(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0), i8* nonnull [[STRING]], i64 5)
+; CHECK-NEXT:    [[CMP:%.*]] = icmp slt i32 [[CALL]], 1
+; CHECK-NEXT:    [[CONV:%.*]] = zext i1 [[CMP]] to i32
+; CHECK-NEXT:    call void @llvm.lifetime.end.p0i8(i64 12, i8* nonnull [[STRING]])
+; CHECK-NEXT:    ret i32 [[CONV]]
+;
+  %string = getelementptr inbounds [12 x i8], [12 x i8]* %buf, i64 0, i64 0
+  call void @llvm.lifetime.start.p0i8(i64 12, i8* nonnull %string)
+  %call = call i32 @strncmp(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0), i8* nonnull %string, i64 5)
+  %cmp = icmp slt i32 %call, 1
+  %conv = zext i1 %cmp to i32
+  call void @llvm.lifetime.end.p0i8(i64 12, i8* nonnull %string)
+  ret i32 %conv
+}
+
+
+define i32 @strncmp_memcmp_bad2([12 x i8]* %buf, i64 %n) {
+; CHECK-LABEL: @strncmp_memcmp_bad2(
+; CHECK-NEXT:    [[STRING:%.*]] = getelementptr inbounds [12 x i8], [12 x i8]* [[BUF:%.*]], i64 0, i64 0
+; CHECK-NEXT:    call void @llvm.lifetime.start.p0i8(i64 12, i8* nonnull [[STRING]])
+; CHECK-NEXT:    [[CALL:%.*]] = call i32 @strncmp(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0), i8* nonnull [[STRING]], i64 [[N:%.*]])
+; CHECK-NEXT:    [[CMP:%.*]] = icmp slt i32 [[CALL]], 1
+; CHECK-NEXT:    [[CONV:%.*]] = zext i1 [[CMP]] to i32
+; CHECK-NEXT:    call void @llvm.lifetime.end.p0i8(i64 12, i8* nonnull [[STRING]])
+; CHECK-NEXT:    ret i32 [[CONV]]
+;
+  %string = getelementptr inbounds [12 x i8], [12 x i8]* %buf, i64 0, i64 0
+  call void @llvm.lifetime.start.p0i8(i64 12, i8* nonnull %string)
+  %call = call i32 @strncmp(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0), i8* nonnull %string, i64 %n)
+  %cmp = icmp slt i32 %call, 1
+  %conv = zext i1 %cmp to i32
+  call void @llvm.lifetime.end.p0i8(i64 12, i8* nonnull %string)
+  ret i32 %conv
+}
+
+
+define i32 @strncmp_memcmp_bad3([12 x i8]* %buf) {
+; CHECK-LABEL: @strncmp_memcmp_bad3(
+; CHECK-NEXT:    [[STRING:%.*]] = getelementptr inbounds [12 x i8], [12 x i8]* [[BUF:%.*]], i64 0, i64 0
+; CHECK-NEXT:    call void @llvm.lifetime.start.p0i8(i64 12, i8* nonnull [[STRING]])
+; CHECK-NEXT:    [[CALL:%.*]] = call i32 @strncmp(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0), i8* nonnull [[STRING]], i64 12)
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i32 [[CALL]], 0
+; CHECK-NEXT:    [[CONV:%.*]] = zext i1 [[CMP]] to i32
+; CHECK-NEXT:    call void @llvm.lifetime.end.p0i8(i64 12, i8* nonnull [[STRING]])
+; CHECK-NEXT:    ret i32 [[CONV]]
+;
+  %string = getelementptr inbounds [12 x i8], [12 x i8]* %buf, i64 0, i64 0
+  call void @llvm.lifetime.start.p0i8(i64 12, i8* nonnull %string)
+  %call = call i32 @strncmp(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0), i8* nonnull %string, i64 12)
+  %cmp = icmp eq i32 %call, 0
+  %conv = zext i1 %cmp to i32
+  call void @llvm.lifetime.end.p0i8(i64 12, i8* nonnull %string)
+  ret i32 %conv
+}
+
+define i32 @strncmp_memcmp_bad4([12 x i8]* %buf) {
+; CHECK-LABEL: @strncmp_memcmp_bad4(
+; CHECK-NEXT:    [[STRING:%.*]] = getelementptr inbounds [12 x i8], [12 x i8]* [[BUF:%.*]], i64 0, i64 0
+; CHECK-NEXT:    call void @llvm.lifetime.start.p0i8(i64 12, i8* nonnull [[STRING]])
+; CHECK-NEXT:    [[CALL:%.*]] = call i32 @strncmp(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0), i8* nonnull [[STRING]], i64 12)
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i32 [[CALL]], 0
+; CHECK-NEXT:    [[CONV:%.*]] = zext i1 [[CMP]] to i32
+; CHECK-NEXT:    call void @llvm.lifetime.end.p0i8(i64 12, i8* nonnull [[STRING]])
+; CHECK-NEXT:    ret i32 [[CONV]]
+;
+  %string = getelementptr inbounds [12 x i8], [12 x i8]* %buf, i64 0, i64 0
+  call void @llvm.lifetime.start.p0i8(i64 12, i8* nonnull %string)
+  %call = call i32 @strncmp(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0), i8* nonnull %string, i64 12)
+  %cmp = icmp eq i32 %call, 0
+  %conv = zext i1 %cmp to i32
+  call void @llvm.lifetime.end.p0i8(i64 12, i8* nonnull %string)
+  ret i32 %conv
+}
+
+define i32 @strncmp_memcmp_bad5(i8* nocapture readonly %k) {
+; CHECK-LABEL: @strncmp_memcmp_bad5(
+; CHECK-NEXT:    [[CALL:%.*]] = tail call i32 @strncmp(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0), i8* [[K:%.*]], i64 2)
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i32 [[CALL]], 0
+; CHECK-NEXT:    [[CONV:%.*]] = zext i1 [[CMP]] to i32
+; CHECK-NEXT:    ret i32 [[CONV]]
+;
+  %call = tail call i32 @strncmp(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0), i8* %k, i64 2)
+  %cmp = icmp eq i32 %call, 0
+  %conv = zext i1 %cmp to i32
+  ret i32 %conv
+}
+
+define i32 @strncmp_memcmp_bad6([4 x i8]* %buf) {
+; CHECK-LABEL: @strncmp_memcmp_bad6(
+; CHECK-NEXT:    [[STRING:%.*]] = getelementptr inbounds [4 x i8], [4 x i8]* [[BUF:%.*]], i64 0, i64 0
+; CHECK-NEXT:    call void @llvm.lifetime.start.p0i8(i64 4, i8* nonnull [[STRING]])
+; CHECK-NEXT:    [[CALL:%.*]] = call i32 @strncmp(i8* nonnull [[STRING]], i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0), i64 2)
+; CHECK-NEXT:    tail call void @use(i32 [[CALL]])
+; CHECK-NEXT:    call void @llvm.lifetime.end.p0i8(i64 4, i8* nonnull [[STRING]])
+; CHECK-NEXT:    ret i32 0
+;
+  %string = getelementptr inbounds [4 x i8], [4 x i8]* %buf, i64 0, i64 0
+  call void @llvm.lifetime.start.p0i8(i64 4, i8* nonnull %string)
+  %call = call i32 @strncmp(i8* nonnull %string, i8* getelementptr inbounds ([4 x i8], [4 x i8]* @key, i64 0, i64 0), i64 2)
+  tail call void @use(i32 %call)
+  call void @llvm.lifetime.end.p0i8(i64 4, i8* nonnull %string)
+  ret i32 0
+}
+
+declare i32 @memcmp(i8* nocapture, i8* nocapture, i64)