Index: lib/Transforms/Utils/SimplifyLibCalls.cpp
===================================================================
--- lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -322,6 +322,12 @@
                       B, DL, TLI);
   }
 
+  // strcmp(x, "x") -> *x == 'x'
+  if ((HasStr1 && Str1.size() == 1) || (HasStr2 && Str2.size() == 1))
+    return emitMemCmp(Str1P, Str2P,
+                      ConstantInt::get(DL.getIntPtrType(CI->getContext()), 1),
+                      B, DL, TLI);
+
   return nullptr;
 }
 
Index: test/Transforms/InstCombine/strcmp-1.ll
===================================================================
--- test/Transforms/InstCombine/strcmp-1.ll
+++ test/Transforms/InstCombine/strcmp-1.ll
@@ -1,3 +1,4 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
 ; Test that the strcmp library call simplifier works correctly.
 ; RUN: opt < %s -instcombine -S | FileCheck %s
 
@@ -6,6 +7,7 @@
 @hello = constant [6 x i8] c"hello\00"
 @hell = constant [5 x i8] c"hell\00"
 @bell = constant [5 x i8] c"bell\00"
+@str_single_char = constant [2 x i8] c".\00"
 @null = constant [1 x i8] zeroinitializer
 
 declare i32 @strcmp(i8*, i8*)
@@ -13,10 +15,11 @@
 ; strcmp("", x) -> -*x
 define i32 @test1(i8* %str2) {
 ; CHECK-LABEL: @test1(
-; CHECK: %strcmpload = load i8, i8* %str
-; CHECK: %1 = zext i8 %strcmpload to i32
-; CHECK: %2 = sub nsw i32 0, %1
-; CHECK: ret i32 %2
+; CHECK-NEXT:    [[STRCMPLOAD:%.*]] = load i8, i8* [[STR2:%.*]], align 1
+; CHECK-NEXT:    [[TMP1:%.*]] = zext i8 [[STRCMPLOAD]] to i32
+; CHECK-NEXT:    [[TMP2:%.*]] = sub nsw i32 0, [[TMP1]]
+; CHECK-NEXT:    ret i32 [[TMP2]]
+;
 
   %str1 = getelementptr inbounds [1 x i8], [1 x i8]* @null, i32 0, i32 0
   %temp1 = call i32 @strcmp(i8* %str1, i8* %str2)
@@ -27,9 +30,10 @@
 ; strcmp(x, "") -> *x
 define i32 @test2(i8* %str1) {
 ; CHECK-LABEL: @test2(
-; CHECK: %strcmpload = load i8, i8* %str
-; CHECK: %1 = zext i8 %strcmpload to i32
-; CHECK: ret i32 %1
+; CHECK-NEXT:    [[STRCMPLOAD:%.*]] = load i8, i8* [[STR1:%.*]], align 1
+; CHECK-NEXT:    [[TMP1:%.*]] = zext i8 [[STRCMPLOAD]] to i32
+; CHECK-NEXT:    ret i32 [[TMP1]]
+;
 
   %str2 = getelementptr inbounds [1 x i8], [1 x i8]* @null, i32 0, i32 0
   %temp1 = call i32 @strcmp(i8* %str1, i8* %str2)
@@ -39,7 +43,8 @@
 ; strcmp(x, y)  -> cnst
 define i32 @test3() {
 ; CHECK-LABEL: @test3(
-; CHECK: ret i32 -1
+; CHECK-NEXT:    ret i32 -1
+;
 
   %str1 = getelementptr inbounds [5 x i8], [5 x i8]* @hell, i32 0, i32 0
   %str2 = getelementptr inbounds [6 x i8], [6 x i8]* @hello, i32 0, i32 0
@@ -49,7 +54,8 @@
 
 define i32 @test4() {
 ; CHECK-LABEL: @test4(
-; CHECK: ret i32 1
+; CHECK-NEXT:    ret i32 1
+;
 
   %str1 = getelementptr inbounds [5 x i8], [5 x i8]* @hell, i32 0, i32 0
   %str2 = getelementptr inbounds [1 x i8], [1 x i8]* @null, i32 0, i32 0
@@ -61,8 +67,10 @@
 ; (This transform is rather difficult to trigger in a useful manner)
 define i32 @test5(i1 %b) {
 ; CHECK-LABEL: @test5(
-; CHECK: %memcmp = call i32 @memcmp(i8* getelementptr inbounds ([6 x i8], [6 x i8]* @hello, i32 0, i32 0), i8* %str2, i32 5)
-; CHECK: ret i32 %memcmp
+; CHECK-NEXT:    [[STR2:%.*]] = select i1 [[B:%.*]], i8* getelementptr inbounds ([5 x i8], [5 x i8]* @hell, i32 0, i32 0), i8* getelementptr inbounds ([5 x i8], [5 x i8]* @bell, i32 0, i32 0)
+; CHECK-NEXT:    [[MEMCMP:%.*]] = call i32 @memcmp(i8* getelementptr inbounds ([6 x i8], [6 x i8]* @hello, i32 0, i32 0), i8* [[STR2]], i32 5)
+; CHECK-NEXT:    ret i32 [[MEMCMP]]
+;
 
   %str1 = getelementptr inbounds [6 x i8], [6 x i8]* @hello, i32 0, i32 0
   %temp1 = getelementptr inbounds [5 x i8], [5 x i8]* @hell, i32 0, i32 0
@@ -75,8 +83,37 @@
 ; strcmp(x,x)  -> 0
 define i32 @test6(i8* %str) {
 ; CHECK-LABEL: @test6(
-; CHECK: ret i32 0
+; CHECK-NEXT:    ret i32 0
+;
 
   %temp1 = call i32 @strcmp(i8* %str, i8* %str)
   ret i32 %temp1
 }
+
+; strcmp(x,"x")  -> *x == 'x'
+define i32 @compare_single_char(i8* %s) {
+; CHECK-LABEL: @compare_single_char(
+; CHECK-NEXT:    [[LHSC:%.*]] = load i8, i8* [[S:%.*]], align 1
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i8 [[LHSC]], 46
+; CHECK-NEXT:    [[CONV:%.*]] = zext i1 [[CMP]] to i32
+; CHECK-NEXT:    ret i32 [[CONV]]
+;
+  %call = tail call i32 @strcmp(i8* %s, i8* getelementptr inbounds ([2 x i8], [2 x i8]* @str_single_char, i64 0, i64 0)) #2
+  %cmp = icmp eq i32 %call, 0
+  %conv = zext i1 %cmp to i32
+  ret i32 %conv
+}
+
+; strcmp("x", x)  -> *x == 'x'
+define i32 @compare_single_char_rev(i8* %s) {
+; CHECK-LABEL: @compare_single_char_rev(
+; CHECK-NEXT:    [[RHSC:%.*]] = load i8, i8* [[S:%.*]], align 1
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i8 [[RHSC]], 46
+; CHECK-NEXT:    [[CONV:%.*]] = zext i1 [[CMP]] to i32
+; CHECK-NEXT:    ret i32 [[CONV]]
+;
+  %call = tail call i32 @strcmp(i8* getelementptr inbounds ([2 x i8], [2 x i8]* @str_single_char, i64 0, i64 0), i8* %s) #2
+  %cmp = icmp eq i32 %call, 0
+  %conv = zext i1 %cmp to i32
+  ret i32 %conv
+}