Index: llvm/lib/Transforms/AggressiveInstCombine/AggressiveInstCombine.cpp
===================================================================
--- llvm/lib/Transforms/AggressiveInstCombine/AggressiveInstCombine.cpp
+++ llvm/lib/Transforms/AggressiveInstCombine/AggressiveInstCombine.cpp
@@ -906,7 +906,7 @@
   return false;
 }
 
-/// Try to expand strcmp(P, "x") calls.
+/// Try to expand strcmp(P, "x"), strcmp(P, "xy") calls.
 static bool expandStrcmp(CallInst *CI, DominatorTree &DT, bool &MadeCFGChange) {
   Value *Str1P = CI->getArgOperand(0), *Str2P = CI->getArgOperand(1);
 
@@ -921,10 +921,10 @@
   Value *NonConstantP = nullptr;
   StringRef ConstantStr;
 
-  if (!HasStr1 && HasStr2 && Str2.size() == 1) {
+  if (!HasStr1 && HasStr2 && (Str2.size() == 1 || Str2.size() == 2)) {
     NonConstantP = Str1P;
     ConstantStr = Str2;
-  } else if (!HasStr2 && HasStr1 && Str1.size() == 1) {
+  } else if (!HasStr2 && HasStr1 && (Str1.size() == 1 || Str1.size() == 2)) {
     NonConstantP = Str2P;
     ConstantStr = Str1;
   } else {
@@ -946,6 +946,19 @@
   //   v1 = P[1]
   // dst = phi(v0, v1)
   //
+  // For strcmp(P, "xy") do the following transformation:
+  //
+  // (before)
+  // dst = strcmp(P, "x")
+  //
+  // (after)
+  // v0 = P[0] - 'x'
+  // [if v0 == 0]
+  //   v1 = P[1] - 'y'
+  //   [if v1 == 0]
+  //     v2 = P[2]
+  // dst = phi(v0, v1, v2)
+  //
 
   IRBuilder<> B(CI->getParent());
   DomTreeUpdater DTU(DT, DomTreeUpdater::UpdateStrategy::Lazy);
@@ -966,6 +979,8 @@
       IsFirstCharacterSubZero, CI, /*Unreachable*/ false,
       /*BranchWeights*/ nullptr, &DTU);
 
+  BasicBlock *StrcmpExpandSubJoinBB = CI->getParent();
+
   B.SetInsertPoint(IsFirstCharacterSubZeroBBTerminator);
   B.GetInsertBlock()->setName("strcmp_expand_sub_is_zero");
   BasicBlock *IsFirstCharacterSubZeroBB = B.GetInsertBlock();
@@ -973,13 +988,48 @@
       B.CreateLoad(B.getInt8Ty(), B.CreateConstInBoundsGEP1_64(
                                       B.getInt8Ty(), NonConstantP, 1)),
       RetType);
+  Value *IsFirstCharacterSubZeroResult = Str1SecondCharacterValue;
+
+  bool TwoCharacterConstantStr = ConstantStr.size() == 2;
+  BasicBlock *IsSecondCharacterSubZeroBB = nullptr;
+  Value *Str1ThirdCharacterValue = nullptr;
+
+  if (TwoCharacterConstantStr) {
+    Value *Str2SecondCharacterValue =
+        ConstantInt::get(RetType, static_cast<unsigned char>(ConstantStr[1]));
+    Value *SecondCharacterSub =
+        B.CreateNSWSub(Str1SecondCharacterValue, Str2SecondCharacterValue);
+    IsFirstCharacterSubZeroResult = SecondCharacterSub;
+    Value *IsSecondCharacterSubZero =
+        B.CreateICmpEQ(SecondCharacterSub, ConstantInt::get(RetType, 0));
+    IsSecondCharacterSubZeroBB =
+        BasicBlock::Create(B.getContext(), "strcmp_expand_sub_is_zero",
+                           InitialBB->getParent(), StrcmpExpandSubJoinBB);
+
+    B.CreateCondBr(IsSecondCharacterSubZero, IsSecondCharacterSubZeroBB,
+                   StrcmpExpandSubJoinBB);
+    IsFirstCharacterSubZeroBBTerminator->eraseFromParent();
+
+    B.SetInsertPoint(IsSecondCharacterSubZeroBB);
+    Str1ThirdCharacterValue = B.CreateZExt(
+        B.CreateLoad(B.getInt8Ty(), B.CreateConstInBoundsGEP1_64(
+                                        B.getInt8Ty(), NonConstantP, 2)),
+        RetType);
+    B.CreateBr(StrcmpExpandSubJoinBB);
+
+    DTU.applyUpdates({{DominatorTree::Insert, IsSecondCharacterSubZeroBB,
+                       StrcmpExpandSubJoinBB}});
+  }
 
   B.SetInsertPoint(CI);
-  B.GetInsertBlock()->setName("strcmp_expand_sub_join");
+  StrcmpExpandSubJoinBB->setName("strcmp_expand_sub_join");
 
-  PHINode *Result = B.CreatePHI(RetType, 2);
+  PHINode *Result = B.CreatePHI(RetType, 2 + TwoCharacterConstantStr);
   Result->addIncoming(FirstCharacterSub, InitialBB);
-  Result->addIncoming(Str1SecondCharacterValue, IsFirstCharacterSubZeroBB);
+  Result->addIncoming(IsFirstCharacterSubZeroResult, IsFirstCharacterSubZeroBB);
+
+  if (TwoCharacterConstantStr)
+    Result->addIncoming(Str1ThirdCharacterValue, IsSecondCharacterSubZeroBB);
 
   CI->replaceAllUsesWith(Result);
   CI->eraseFromParent();
Index: llvm/test/Transforms/AggressiveInstCombine/strcmp.ll
===================================================================
--- llvm/test/Transforms/AggressiveInstCombine/strcmp.ll
+++ llvm/test/Transforms/AggressiveInstCombine/strcmp.ll
@@ -209,8 +209,26 @@
 
 define i1 @expand_strcmp_eq_s2(ptr %C) {
 ; CHECK-LABEL: @expand_strcmp_eq_s2(
-; CHECK-NEXT:    [[CALL:%.*]] = call i32 @strcmp(ptr [[C:%.*]], ptr @s2)
-; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i32 [[CALL]], 0
+; CHECK-NEXT:    [[TMP1:%.*]] = load i8, ptr [[C:%.*]], align 1
+; CHECK-NEXT:    [[TMP2:%.*]] = zext i8 [[TMP1]] to i32
+; CHECK-NEXT:    [[TMP3:%.*]] = sub nsw i32 [[TMP2]], 48
+; CHECK-NEXT:    [[TMP4:%.*]] = icmp eq i32 [[TMP3]], 0
+; CHECK-NEXT:    br i1 [[TMP4]], label [[STRCMP_EXPAND_SUB_IS_ZERO:%.*]], label [[STRCMP_EXPAND_SUB_JOIN:%.*]]
+; CHECK:       strcmp_expand_sub_is_zero:
+; CHECK-NEXT:    [[TMP5:%.*]] = getelementptr inbounds i8, ptr [[C]], i64 1
+; CHECK-NEXT:    [[TMP6:%.*]] = load i8, ptr [[TMP5]], align 1
+; CHECK-NEXT:    [[TMP7:%.*]] = zext i8 [[TMP6]] to i32
+; CHECK-NEXT:    [[TMP8:%.*]] = sub nsw i32 [[TMP7]], 49
+; CHECK-NEXT:    [[TMP9:%.*]] = icmp eq i32 [[TMP8]], 0
+; CHECK-NEXT:    br i1 [[TMP9]], label [[STRCMP_EXPAND_SUB_IS_ZERO1:%.*]], label [[STRCMP_EXPAND_SUB_JOIN]]
+; CHECK:       strcmp_expand_sub_is_zero1:
+; CHECK-NEXT:    [[TMP10:%.*]] = getelementptr inbounds i8, ptr [[C]], i64 2
+; CHECK-NEXT:    [[TMP11:%.*]] = load i8, ptr [[TMP10]], align 1
+; CHECK-NEXT:    [[TMP12:%.*]] = zext i8 [[TMP11]] to i32
+; CHECK-NEXT:    br label [[STRCMP_EXPAND_SUB_JOIN]]
+; CHECK:       strcmp_expand_sub_join:
+; CHECK-NEXT:    [[TMP13:%.*]] = phi i32 [ [[TMP3]], [[TMP0:%.*]] ], [ [[TMP8]], [[STRCMP_EXPAND_SUB_IS_ZERO]] ], [ [[TMP12]], [[STRCMP_EXPAND_SUB_IS_ZERO1]] ]
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i32 [[TMP13]], 0
 ; CHECK-NEXT:    ret i1 [[CMP]]
 ;
   %call = call i32 @strcmp(ptr %C, ptr @s2)
@@ -220,8 +238,26 @@
 
 define i1 @expand_strcmp_ne_s2(ptr %C) {
 ; CHECK-LABEL: @expand_strcmp_ne_s2(
-; CHECK-NEXT:    [[CALL:%.*]] = call i32 @strcmp(ptr [[C:%.*]], ptr @s2)
-; CHECK-NEXT:    [[CMP:%.*]] = icmp ne i32 [[CALL]], 0
+; CHECK-NEXT:    [[TMP1:%.*]] = load i8, ptr [[C:%.*]], align 1
+; CHECK-NEXT:    [[TMP2:%.*]] = zext i8 [[TMP1]] to i32
+; CHECK-NEXT:    [[TMP3:%.*]] = sub nsw i32 [[TMP2]], 48
+; CHECK-NEXT:    [[TMP4:%.*]] = icmp eq i32 [[TMP3]], 0
+; CHECK-NEXT:    br i1 [[TMP4]], label [[STRCMP_EXPAND_SUB_IS_ZERO:%.*]], label [[STRCMP_EXPAND_SUB_JOIN:%.*]]
+; CHECK:       strcmp_expand_sub_is_zero:
+; CHECK-NEXT:    [[TMP5:%.*]] = getelementptr inbounds i8, ptr [[C]], i64 1
+; CHECK-NEXT:    [[TMP6:%.*]] = load i8, ptr [[TMP5]], align 1
+; CHECK-NEXT:    [[TMP7:%.*]] = zext i8 [[TMP6]] to i32
+; CHECK-NEXT:    [[TMP8:%.*]] = sub nsw i32 [[TMP7]], 49
+; CHECK-NEXT:    [[TMP9:%.*]] = icmp eq i32 [[TMP8]], 0
+; CHECK-NEXT:    br i1 [[TMP9]], label [[STRCMP_EXPAND_SUB_IS_ZERO1:%.*]], label [[STRCMP_EXPAND_SUB_JOIN]]
+; CHECK:       strcmp_expand_sub_is_zero1:
+; CHECK-NEXT:    [[TMP10:%.*]] = getelementptr inbounds i8, ptr [[C]], i64 2
+; CHECK-NEXT:    [[TMP11:%.*]] = load i8, ptr [[TMP10]], align 1
+; CHECK-NEXT:    [[TMP12:%.*]] = zext i8 [[TMP11]] to i32
+; CHECK-NEXT:    br label [[STRCMP_EXPAND_SUB_JOIN]]
+; CHECK:       strcmp_expand_sub_join:
+; CHECK-NEXT:    [[TMP13:%.*]] = phi i32 [ [[TMP3]], [[TMP0:%.*]] ], [ [[TMP8]], [[STRCMP_EXPAND_SUB_IS_ZERO]] ], [ [[TMP12]], [[STRCMP_EXPAND_SUB_IS_ZERO1]] ]
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ne i32 [[TMP13]], 0
 ; CHECK-NEXT:    ret i1 [[CMP]]
 ;
   %call = call i32 @strcmp(ptr %C, ptr @s2)
@@ -231,8 +267,26 @@
 
 define i1 @expand_strcmp_sgt_s2(ptr %C) {
 ; CHECK-LABEL: @expand_strcmp_sgt_s2(
-; CHECK-NEXT:    [[CALL:%.*]] = call i32 @strcmp(ptr [[C:%.*]], ptr @s2)
-; CHECK-NEXT:    [[CMP:%.*]] = icmp sgt i32 [[CALL]], 0
+; CHECK-NEXT:    [[TMP1:%.*]] = load i8, ptr [[C:%.*]], align 1
+; CHECK-NEXT:    [[TMP2:%.*]] = zext i8 [[TMP1]] to i32
+; CHECK-NEXT:    [[TMP3:%.*]] = sub nsw i32 [[TMP2]], 48
+; CHECK-NEXT:    [[TMP4:%.*]] = icmp eq i32 [[TMP3]], 0
+; CHECK-NEXT:    br i1 [[TMP4]], label [[STRCMP_EXPAND_SUB_IS_ZERO:%.*]], label [[STRCMP_EXPAND_SUB_JOIN:%.*]]
+; CHECK:       strcmp_expand_sub_is_zero:
+; CHECK-NEXT:    [[TMP5:%.*]] = getelementptr inbounds i8, ptr [[C]], i64 1
+; CHECK-NEXT:    [[TMP6:%.*]] = load i8, ptr [[TMP5]], align 1
+; CHECK-NEXT:    [[TMP7:%.*]] = zext i8 [[TMP6]] to i32
+; CHECK-NEXT:    [[TMP8:%.*]] = sub nsw i32 [[TMP7]], 49
+; CHECK-NEXT:    [[TMP9:%.*]] = icmp eq i32 [[TMP8]], 0
+; CHECK-NEXT:    br i1 [[TMP9]], label [[STRCMP_EXPAND_SUB_IS_ZERO1:%.*]], label [[STRCMP_EXPAND_SUB_JOIN]]
+; CHECK:       strcmp_expand_sub_is_zero1:
+; CHECK-NEXT:    [[TMP10:%.*]] = getelementptr inbounds i8, ptr [[C]], i64 2
+; CHECK-NEXT:    [[TMP11:%.*]] = load i8, ptr [[TMP10]], align 1
+; CHECK-NEXT:    [[TMP12:%.*]] = zext i8 [[TMP11]] to i32
+; CHECK-NEXT:    br label [[STRCMP_EXPAND_SUB_JOIN]]
+; CHECK:       strcmp_expand_sub_join:
+; CHECK-NEXT:    [[TMP13:%.*]] = phi i32 [ [[TMP3]], [[TMP0:%.*]] ], [ [[TMP8]], [[STRCMP_EXPAND_SUB_IS_ZERO]] ], [ [[TMP12]], [[STRCMP_EXPAND_SUB_IS_ZERO1]] ]
+; CHECK-NEXT:    [[CMP:%.*]] = icmp sgt i32 [[TMP13]], 0
 ; CHECK-NEXT:    ret i1 [[CMP]]
 ;
   %call = call i32 @strcmp(ptr %C, ptr @s2)
@@ -242,8 +296,26 @@
 
 define i1 @expand_strcmp_sge_s2(ptr %C) {
 ; CHECK-LABEL: @expand_strcmp_sge_s2(
-; CHECK-NEXT:    [[CALL:%.*]] = call i32 @strcmp(ptr [[C:%.*]], ptr @s2)
-; CHECK-NEXT:    [[CMP:%.*]] = icmp sge i32 [[CALL]], 0
+; CHECK-NEXT:    [[TMP1:%.*]] = load i8, ptr [[C:%.*]], align 1
+; CHECK-NEXT:    [[TMP2:%.*]] = zext i8 [[TMP1]] to i32
+; CHECK-NEXT:    [[TMP3:%.*]] = sub nsw i32 [[TMP2]], 48
+; CHECK-NEXT:    [[TMP4:%.*]] = icmp eq i32 [[TMP3]], 0
+; CHECK-NEXT:    br i1 [[TMP4]], label [[STRCMP_EXPAND_SUB_IS_ZERO:%.*]], label [[STRCMP_EXPAND_SUB_JOIN:%.*]]
+; CHECK:       strcmp_expand_sub_is_zero:
+; CHECK-NEXT:    [[TMP5:%.*]] = getelementptr inbounds i8, ptr [[C]], i64 1
+; CHECK-NEXT:    [[TMP6:%.*]] = load i8, ptr [[TMP5]], align 1
+; CHECK-NEXT:    [[TMP7:%.*]] = zext i8 [[TMP6]] to i32
+; CHECK-NEXT:    [[TMP8:%.*]] = sub nsw i32 [[TMP7]], 49
+; CHECK-NEXT:    [[TMP9:%.*]] = icmp eq i32 [[TMP8]], 0
+; CHECK-NEXT:    br i1 [[TMP9]], label [[STRCMP_EXPAND_SUB_IS_ZERO1:%.*]], label [[STRCMP_EXPAND_SUB_JOIN]]
+; CHECK:       strcmp_expand_sub_is_zero1:
+; CHECK-NEXT:    [[TMP10:%.*]] = getelementptr inbounds i8, ptr [[C]], i64 2
+; CHECK-NEXT:    [[TMP11:%.*]] = load i8, ptr [[TMP10]], align 1
+; CHECK-NEXT:    [[TMP12:%.*]] = zext i8 [[TMP11]] to i32
+; CHECK-NEXT:    br label [[STRCMP_EXPAND_SUB_JOIN]]
+; CHECK:       strcmp_expand_sub_join:
+; CHECK-NEXT:    [[TMP13:%.*]] = phi i32 [ [[TMP3]], [[TMP0:%.*]] ], [ [[TMP8]], [[STRCMP_EXPAND_SUB_IS_ZERO]] ], [ [[TMP12]], [[STRCMP_EXPAND_SUB_IS_ZERO1]] ]
+; CHECK-NEXT:    [[CMP:%.*]] = icmp sge i32 [[TMP13]], 0
 ; CHECK-NEXT:    ret i1 [[CMP]]
 ;
   %call = call i32 @strcmp(ptr %C, ptr @s2)
@@ -253,8 +325,26 @@
 
 define i1 @expand_strcmp_slt_s2(ptr %C) {
 ; CHECK-LABEL: @expand_strcmp_slt_s2(
-; CHECK-NEXT:    [[CALL:%.*]] = call i32 @strcmp(ptr [[C:%.*]], ptr @s2)
-; CHECK-NEXT:    [[CMP:%.*]] = icmp slt i32 [[CALL]], 0
+; CHECK-NEXT:    [[TMP1:%.*]] = load i8, ptr [[C:%.*]], align 1
+; CHECK-NEXT:    [[TMP2:%.*]] = zext i8 [[TMP1]] to i32
+; CHECK-NEXT:    [[TMP3:%.*]] = sub nsw i32 [[TMP2]], 48
+; CHECK-NEXT:    [[TMP4:%.*]] = icmp eq i32 [[TMP3]], 0
+; CHECK-NEXT:    br i1 [[TMP4]], label [[STRCMP_EXPAND_SUB_IS_ZERO:%.*]], label [[STRCMP_EXPAND_SUB_JOIN:%.*]]
+; CHECK:       strcmp_expand_sub_is_zero:
+; CHECK-NEXT:    [[TMP5:%.*]] = getelementptr inbounds i8, ptr [[C]], i64 1
+; CHECK-NEXT:    [[TMP6:%.*]] = load i8, ptr [[TMP5]], align 1
+; CHECK-NEXT:    [[TMP7:%.*]] = zext i8 [[TMP6]] to i32
+; CHECK-NEXT:    [[TMP8:%.*]] = sub nsw i32 [[TMP7]], 49
+; CHECK-NEXT:    [[TMP9:%.*]] = icmp eq i32 [[TMP8]], 0
+; CHECK-NEXT:    br i1 [[TMP9]], label [[STRCMP_EXPAND_SUB_IS_ZERO1:%.*]], label [[STRCMP_EXPAND_SUB_JOIN]]
+; CHECK:       strcmp_expand_sub_is_zero1:
+; CHECK-NEXT:    [[TMP10:%.*]] = getelementptr inbounds i8, ptr [[C]], i64 2
+; CHECK-NEXT:    [[TMP11:%.*]] = load i8, ptr [[TMP10]], align 1
+; CHECK-NEXT:    [[TMP12:%.*]] = zext i8 [[TMP11]] to i32
+; CHECK-NEXT:    br label [[STRCMP_EXPAND_SUB_JOIN]]
+; CHECK:       strcmp_expand_sub_join:
+; CHECK-NEXT:    [[TMP13:%.*]] = phi i32 [ [[TMP3]], [[TMP0:%.*]] ], [ [[TMP8]], [[STRCMP_EXPAND_SUB_IS_ZERO]] ], [ [[TMP12]], [[STRCMP_EXPAND_SUB_IS_ZERO1]] ]
+; CHECK-NEXT:    [[CMP:%.*]] = icmp slt i32 [[TMP13]], 0
 ; CHECK-NEXT:    ret i1 [[CMP]]
 ;
   %call = call i32 @strcmp(ptr %C, ptr @s2)
@@ -264,8 +354,26 @@
 
 define i1 @expand_strcmp_sle_s2(ptr %C) {
 ; CHECK-LABEL: @expand_strcmp_sle_s2(
-; CHECK-NEXT:    [[CALL:%.*]] = call i32 @strcmp(ptr [[C:%.*]], ptr @s2)
-; CHECK-NEXT:    [[CMP:%.*]] = icmp sle i32 [[CALL]], 0
+; CHECK-NEXT:    [[TMP1:%.*]] = load i8, ptr [[C:%.*]], align 1
+; CHECK-NEXT:    [[TMP2:%.*]] = zext i8 [[TMP1]] to i32
+; CHECK-NEXT:    [[TMP3:%.*]] = sub nsw i32 [[TMP2]], 48
+; CHECK-NEXT:    [[TMP4:%.*]] = icmp eq i32 [[TMP3]], 0
+; CHECK-NEXT:    br i1 [[TMP4]], label [[STRCMP_EXPAND_SUB_IS_ZERO:%.*]], label [[STRCMP_EXPAND_SUB_JOIN:%.*]]
+; CHECK:       strcmp_expand_sub_is_zero:
+; CHECK-NEXT:    [[TMP5:%.*]] = getelementptr inbounds i8, ptr [[C]], i64 1
+; CHECK-NEXT:    [[TMP6:%.*]] = load i8, ptr [[TMP5]], align 1
+; CHECK-NEXT:    [[TMP7:%.*]] = zext i8 [[TMP6]] to i32
+; CHECK-NEXT:    [[TMP8:%.*]] = sub nsw i32 [[TMP7]], 49
+; CHECK-NEXT:    [[TMP9:%.*]] = icmp eq i32 [[TMP8]], 0
+; CHECK-NEXT:    br i1 [[TMP9]], label [[STRCMP_EXPAND_SUB_IS_ZERO1:%.*]], label [[STRCMP_EXPAND_SUB_JOIN]]
+; CHECK:       strcmp_expand_sub_is_zero1:
+; CHECK-NEXT:    [[TMP10:%.*]] = getelementptr inbounds i8, ptr [[C]], i64 2
+; CHECK-NEXT:    [[TMP11:%.*]] = load i8, ptr [[TMP10]], align 1
+; CHECK-NEXT:    [[TMP12:%.*]] = zext i8 [[TMP11]] to i32
+; CHECK-NEXT:    br label [[STRCMP_EXPAND_SUB_JOIN]]
+; CHECK:       strcmp_expand_sub_join:
+; CHECK-NEXT:    [[TMP13:%.*]] = phi i32 [ [[TMP3]], [[TMP0:%.*]] ], [ [[TMP8]], [[STRCMP_EXPAND_SUB_IS_ZERO]] ], [ [[TMP12]], [[STRCMP_EXPAND_SUB_IS_ZERO1]] ]
+; CHECK-NEXT:    [[CMP:%.*]] = icmp sle i32 [[TMP13]], 0
 ; CHECK-NEXT:    ret i1 [[CMP]]
 ;
   %call = call i32 @strcmp(ptr %C, ptr @s2)