Index: lib/Analysis/InlineCost.cpp
===================================================================
--- lib/Analysis/InlineCost.cpp
+++ lib/Analysis/InlineCost.cpp
@@ -241,6 +241,7 @@
   bool visitCallSite(CallSite CS);
   bool visitReturnInst(ReturnInst &RI);
   bool visitBranchInst(BranchInst &BI);
+  bool visitSelectInst(SelectInst &SI);
   bool visitSwitchInst(SwitchInst &SI);
   bool visitIndirectBrInst(IndirectBrInst &IBI);
   bool visitResumeInst(ResumeInst &RI);
@@ -1177,6 +1178,86 @@
              SimplifiedValues.lookup(BI.getCondition()));
 }
 
+bool CallAnalyzer::visitSelectInst(SelectInst &SI) {
+  bool CheckSROA = SI.getType()->isPointerTy();
+  Value *TrueVal = SI.getTrueValue();
+  Value *FalseVal = SI.getFalseValue();
+
+  Constant *TrueC = dyn_cast<Constant>(TrueVal);
+  if (!TrueC)
+    TrueC = SimplifiedValues.lookup(TrueVal);
+  Constant *FalseC = dyn_cast<Constant>(FalseVal);
+  if (!FalseC)
+    FalseC = SimplifiedValues.lookup(FalseVal);
+  Constant *CondC =
+      dyn_cast_or_null<Constant>(SimplifiedValues.lookup(SI.getCondition()));
+
+  if (!CondC) {
+    // Select C, X, X => X
+    if (TrueC == FalseC && TrueC) {
+      SimplifiedValues[&SI] = TrueC;
+      return true;
+    }
+
+    if (CheckSROA) {
+      std::pair<Value *, APInt> TrueBaseAndOffset =
+          ConstantOffsetPtrs.lookup(TrueVal);
+      std::pair<Value *, APInt> FalseBaseAndOffset =
+          ConstantOffsetPtrs.lookup(FalseVal);
+      if (TrueBaseAndOffset.first && FalseBaseAndOffset.first &&
+          TrueBaseAndOffset == FalseBaseAndOffset) {
+        ConstantOffsetPtrs[&SI] = TrueBaseAndOffset;
+
+        Value *SROAArg;
+        DenseMap<Value *, int>::iterator CostIt;
+        if (lookupSROAArgAndCost(TrueVal, SROAArg, CostIt))
+          SROAArgValues[&SI] = SROAArg;
+        return true;
+      }
+    }
+
+    return Base::visitSelectInst(SI);
+  }
+
+  // Select condition is a constant.
+  Value *SelectedV = CondC->isAllOnesValue()
+                         ? TrueVal
+                         : (CondC->isNullValue()) ? FalseVal : nullptr;
+  if (!SelectedV) {
+    // Condition is a vector constant that is not all 1s or all 0s.  If all
+    // operands are constants, ConstantExpr::getSelect() can handle the cases
+    // such as select vectors.
+    if (TrueC && FalseC) {
+      if (auto *C = ConstantExpr::getSelect(CondC, TrueC, FalseC)) {
+        SimplifiedValues[&SI] = C;
+        return true;
+      }
+    }
+    return Base::visitSelectInst(SI);
+  }
+
+  // Condition is either all 1s or all 0s. SI can be simplified.
+  if (Constant *SelectedC = dyn_cast<Constant>(SelectedV)) {
+    SimplifiedValues[&SI] = SelectedC;
+    return true;
+  }
+
+  if (CheckSROA) {
+    std::pair<Value *, APInt> BaseAndOffset =
+        ConstantOffsetPtrs.lookup(SelectedV);
+    if (BaseAndOffset.first) {
+      ConstantOffsetPtrs[&SI] = BaseAndOffset;
+
+      Value *SROAArg;
+      DenseMap<Value *, int>::iterator CostIt;
+      if (lookupSROAArgAndCost(SelectedV, SROAArg, CostIt))
+        SROAArgValues[&SI] = SROAArg;
+    }
+  }
+
+  return true;
+}
+
 bool CallAnalyzer::visitSwitchInst(SwitchInst &SI) {
   // We model unconditional switches as free, see the comments on handling
   // branches.
Index: test/Transforms/Inline/AArch64/select.ll
===================================================================
--- /dev/null
+++ test/Transforms/Inline/AArch64/select.ll
@@ -0,0 +1,251 @@
+; RUN: opt -inline -mtriple=aarch64--linux-gnu -S -o - < %s -inline-threshold=0 | FileCheck %s
+
+target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
+target triple = "aarch64--linux-gnu"
+
+declare void @pad()
+@glbl = external global i32
+
+define i32 @outer1(i1 %cond) {
+; CHECK-LABEL: @outer1(
+; CHECK-NOT: call i32 @inner1
+  %C = call i32 @inner1(i1 %cond, i32 1)
+  ret i32 %C
+}
+
+define i32 @inner1(i1 %cond, i32 %val) {
+  %select = select i1 %cond, i32 1, i32 %val       ; Simplified to 1
+  call void @pad()
+  store i32 0, i32* @glbl
+  ret i32 %select                                  ; Simplifies to ret i32 1
+}
+
+
+define i32 @outer2(i32 %val) {
+; CHECK-LABEL: @outer2(
+; CHECK-NOT: call i32 @inner2
+  %C = call i32 @inner2(i1 true, i32 %val)
+  ret i32 %C
+}
+
+define i32 @inner2(i1 %cond, i32 %val) {
+  %select = select i1 %cond, i32 1, i32 %val       ; Simplifies to 1
+  call void @pad()
+  store i32 0, i32* @glbl
+  ret i32 %select                                  ; Simplifies to ret i32 1
+}
+
+
+define i32 @outer3(i32 %val) {
+; CHECK-LABEL: @outer3(
+; CHECK-NOT: call i32 @inner3
+  %C = call i32 @inner3(i1 false, i32 %val)
+  ret i32 %C
+}
+
+define i32 @inner3(i1 %cond, i32 %val) {
+  %select = select i1 %cond, i32 %val, i32 -1      ; Simplifies to -1
+  call void @pad()
+  store i32 0, i32* @glbl
+  ret i32 %select                                  ; Simplifies to ret i32 -1
+}
+
+
+define i32 @outer4() {
+; CHECK-LABEL: @outer4(
+; CHECK-NOT: call i32 @inner4
+  %C = call i32 @inner4(i1 true, i32 1, i32 -1)
+  ret i32 %C
+}
+
+define i32 @inner4(i1 %cond, i32 %val1, i32 %val2) {
+  %select = select i1 %cond, i32 %val1, i32 %val2  ; Simplifies to 1
+  call void @pad()
+  store i32 0, i32* @glbl
+  store i32 1, i32* @glbl
+  ret i32 %select                                  ; Simplifies to ret i32 1
+}
+
+
+define i1 @outer5() {
+; CHECK-LABEL: @outer5(
+; CHECK-NOT: call i1 @inner5
+  %C = call i1 @inner5(i1 true, i1 true, i1 false)
+  ret i1 %C
+}
+
+declare void @dead()
+
+define i1 @inner5(i1 %cond, i1 %val1, i1 %val2) {
+  %select = select i1 %cond, i1 %val1, i1 %val2    ; Simplifies to true
+  br i1 %select, label %exit, label %isfalse       ; Simplifies to br label %end
+
+isfalse:                                           ; This block is unreachable once inlined
+  call void @dead()
+  br label %exit
+
+exit:
+  store i32 0, i32* @glbl
+  ret i1 %select                                   ; Simplifies to ret i1 true
+}
+
+
+define i32 @outer6(i1 %cond) {
+; CHECK-LABEL: @outer6(
+; CHECK-NOT: call i32 @inner6
+  %A = alloca i32
+  %C = call i32 @inner6(i1 %cond, i32* %A)
+  ret i32 %C
+}
+
+define i32 @inner6(i1 %cond, i32* %ptr) {
+  %G1 = getelementptr inbounds i32, i32* %ptr, i32 1
+  %G2 = getelementptr inbounds i32, i32* %G1, i32 1
+  %G3 = getelementptr inbounds i32, i32* %ptr, i32 2
+  %select = select i1 %cond, i32* %G2, i32* %G3    ; Simplified to %A[2]
+  %load = load i32, i32* %select                   ; SROA'ed
+  call void @pad()
+  ret i32 %load                                    ; Simplified
+}
+
+
+define i32 @outer7(i32* %ptr) {
+; CHECK-LABEL: @outer7(
+; CHECK-NOT: call i32 @inner7
+  %A = alloca i32
+  %C = call i32 @inner7(i1 true, i32* %A, i32* %ptr)
+  ret i32 %C
+}
+
+define i32 @inner7(i1 %cond, i32* %p1, i32* %p2) {
+  %select = select i1 %cond, i32* %p1, i32* %p2    ; Simplifies to %A
+  %load = load i32, i32* %select                   ; SROA'ed
+  call void @pad()
+  store i32 0, i32* @glbl
+  ret i32 %load                                    ; Simplified
+}
+
+
+define i32 @outer8(i32* %ptr) {
+; CHECK-LABEL: @outer8(
+; CHECK-NOT: call i32 @inner8
+  %A = alloca i32
+  %C = call i32 @inner8(i1 false, i32* %ptr, i32* %A)
+  ret i32 %C
+}
+
+define i32 @inner8(i1 %cond, i32* %p1, i32* %p2) {
+  %select = select i1 %cond, i32* %p1, i32* %p2    ; Simplifies to %A
+  %load = load i32, i32* %select                   ; SROA'ed
+  call void @pad()
+  store i32 0, i32* @glbl
+  ret i32 %load                                    ; Simplified
+}
+
+
+define <2 x i32> @outer9(<2 x i32> %val) {
+; CHECK-LABEL: @outer9(
+; CHECK-NOT: call <2 x i32> @inner9
+  %C = call <2 x i32> @inner9(<2 x i1> <i1 true, i1 true>, <2 x i32> %val)
+  ret <2 x i32> %C
+}
+
+define <2 x i32> @inner9(<2 x i1> %cond, <2 x i32> %val) {
+  %select = select <2 x i1> %cond, <2 x i32> <i32 1, i32 1>, <2 x i32> %val              ; Simplifies to <1, 1>
+  call void @pad()
+  store i32 0, i32* @glbl
+  ret <2 x i32> %select                                                                  ; Simplifies to ret <2 x i32> <1, 1>
+}
+
+
+define <2 x i32> @outer10(<2 x i32> %val) {
+; CHECK-LABEL: @outer10(
+; CHECK-NOT: call <2 x i32> @inner10
+  %C = call <2 x i32> @inner10(<2 x i1> <i1 false, i1 false>, <2 x i32> %val)
+  ret <2 x i32> %C
+}
+
+define <2 x i32> @inner10(<2 x i1> %cond, <2 x i32> %val) {
+  %select = select <2 x i1> %cond, < 2 x i32> %val, <2 x i32> <i32 -1, i32 -1>           ; Simplifies to <-1, -1>
+  call void @pad()
+  store i32 0, i32* @glbl
+  ret <2 x i32> %select                                                                  ; Simplifies to ret <2 x i32> <-1, -1>
+}
+
+
+define <2 x i32> @outer11() {
+; CHECK-LABEL: @outer11(
+; CHECK-NOT: call <2 x i32> @inner11
+  %C = call <2 x i32> @inner11(<2 x i1> <i1 true, i1 false>)
+  ret <2 x i32> %C
+}
+
+define <2 x i32> @inner11(<2 x i1> %cond) {
+  %select = select <2 x i1> %cond, <2 x i32> <i32 1, i32 1>, < 2 x i32> <i32 -1, i32 -1> ; Simplifies to <1, -1>
+  call void @pad()
+  ret <2 x i32> %select                                                                  ; Simplifies to ret <2 x i32> <1, -1>
+}
+
+
+define i1 @outer12(i32* %ptr) {
+; CHECK-LABEL: @outer12(
+; CHECK-NOT: call i1 @inner12
+  %C = call i1 @inner12(i1 true, i32* @glbl, i32* %ptr)
+  ret i1 %C
+}
+
+define i1 @inner12(i1 %cond, i32* %ptr1, i32* %ptr2) {
+  %select = select i1 %cond, i32* %ptr1, i32* %ptr2 ; Simplified to @glbl
+  %cmp = icmp eq i32* %select, @glbl                ; Simplified to true
+  call void @pad()
+  store i32 0, i32* @glbl
+  ret i1 %cmp                                       ; Simplifies to ret i1 true
+}
+
+
+define <2 x i32> @outer13(<2 x i32> %val1, <2 x i32> %val2) {
+; CHECK-LABEL: @outer13(
+; CHECK: call <2 x i32> @inner13
+  %C = call <2 x i32> @inner13(<2 x i1> <i1 true, i1 false>, <2 x i32> %val1, <2 x i32> %val2)
+  ret <2 x i32> %C
+}
+
+define <2 x i32> @inner13(<2 x i1> %cond, <2 x i32> %val1, < 2 x i32> %val2) {
+  %select = select <2 x i1> %cond, <2 x i32> %val1, < 2 x i32> %val2 ; Cannot be Simplified
+  call void @pad()
+  store i32 0, i32* @glbl
+  store i32 1, i32* @glbl
+  ret <2 x i32> %select                                              ; Simplified
+}
+
+
+define i32 @outer14(i32 %val1, i32 %val2) {
+; CHECK-LABEL: @outer14(
+; CHECK-NOT: call i32 @inner14
+  %C = call i32 @inner14(i1 true, i32 %val1, i32 %val2)
+  ret i32 %C
+}
+
+define i32 @inner14(i1 %cond, i32 %val1, i32 %val2) {
+  %select = select i1 %cond, i32 %val1, i32 %val2   ; Simplified to %val1
+  call void @pad()
+  store i32 0, i32* @glbl
+  store i32 1, i32* @glbl
+  ret i32 %select                                   ; Simplifies to ret i32 %val1
+}
+
+
+define i32 @outer15(i32 %val1, i32 %val2) {
+; CHECK-LABEL: @outer15(
+; CHECK-NOT: call i32 @inner15
+  %C = call i32 @inner15(i1 false, i32 %val1, i32 %val2)
+  ret i32 %C
+}
+
+define i32 @inner15(i1 %cond, i32 %val1, i32 %val2) {
+  %select = select i1 %cond, i32 %val1, i32 %val2   ; Simplified to %val2
+  call void @pad()
+  store i32 0, i32* @glbl
+  store i32 1, i32* @glbl
+  ret i32 %select                                   ; Simplifies to ret i32 %val2
+}