Index: llvm/trunk/lib/Target/ARM/ARMISelLowering.h
===================================================================
--- llvm/trunk/lib/Target/ARM/ARMISelLowering.h
+++ llvm/trunk/lib/Target/ARM/ARMISelLowering.h
@@ -332,6 +332,9 @@
     bool isTruncateFree(Type *SrcTy, Type *DstTy) const override;
     bool isTruncateFree(EVT SrcVT, EVT DstVT) const override;
     bool isZExtFree(SDValue Val, EVT VT2) const override;
+    bool shouldSinkOperands(Instruction *I,
+                            SmallVectorImpl<Use *> &Ops) const override;
+
     bool isFNegFree(EVT VT) const override;
 
     bool isVectorLoadExtDesirable(SDValue ExtVal) const override;
Index: llvm/trunk/lib/Target/ARM/ARMISelLowering.cpp
===================================================================
--- llvm/trunk/lib/Target/ARM/ARMISelLowering.cpp
+++ llvm/trunk/lib/Target/ARM/ARMISelLowering.cpp
@@ -79,6 +79,7 @@
 #include "llvm/IR/IntrinsicInst.h"
 #include "llvm/IR/Intrinsics.h"
 #include "llvm/IR/Module.h"
+#include "llvm/IR/PatternMatch.h"
 #include "llvm/IR/Type.h"
 #include "llvm/IR/User.h"
 #include "llvm/IR/Value.h"
@@ -112,6 +113,7 @@
 #include <vector>
 
 using namespace llvm;
+using namespace llvm::PatternMatch;
 
 #define DEBUG_TYPE "arm-isel"
 
@@ -13146,6 +13148,46 @@
   return false;
 }
 
+/// Check if Ext1 and Ext2 are extends of the same type, doubling the bitwidth
+/// of the vector elements.
+static bool areExtractExts(Value *Ext1, Value *Ext2) {
+  auto areExtDoubled = [](Instruction *Ext) {
+    return Ext->getType()->getScalarSizeInBits() ==
+           2 * Ext->getOperand(0)->getType()->getScalarSizeInBits();
+  };
+
+  if (!match(Ext1, m_ZExtOrSExt(m_Value())) ||
+      !match(Ext2, m_ZExtOrSExt(m_Value())) ||
+      !areExtDoubled(cast<Instruction>(Ext1)) ||
+      !areExtDoubled(cast<Instruction>(Ext2)))
+    return false;
+
+  return true;
+}
+
+/// Check if sinking \p I's operands to I's basic block is profitable, because
+/// the operands can be folded into a target instruction, e.g.
+/// sext/zext can be folded into vsubl.
+bool ARMTargetLowering::shouldSinkOperands(Instruction *I,
+                                           SmallVectorImpl<Use *> &Ops) const {
+  if (!Subtarget->hasNEON() || !I->getType()->isVectorTy())
+    return false;
+
+  switch (I->getOpcode()) {
+  case Instruction::Sub:
+  case Instruction::Add: {
+    if (!areExtractExts(I->getOperand(0), I->getOperand(1)))
+      return false;
+    Ops.push_back(&I->getOperandUse(0));
+    Ops.push_back(&I->getOperandUse(1));
+    return true;
+  }
+  default:
+    return false;
+  }
+  return false;
+}
+
 bool ARMTargetLowering::isVectorLoadExtDesirable(SDValue ExtVal) const {
   EVT VT = ExtVal.getValueType();
 
Index: llvm/trunk/test/Transforms/CodeGenPrepare/ARM/sink-free-instructions.ll
===================================================================
--- llvm/trunk/test/Transforms/CodeGenPrepare/ARM/sink-free-instructions.ll
+++ llvm/trunk/test/Transforms/CodeGenPrepare/ARM/sink-free-instructions.ll
@@ -0,0 +1,232 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -mtriple=armv7-apple-darwin < %s -codegenprepare -S | FileCheck -check-prefix=NEON %s
+; RUN: opt -mtriple=armv6-unknown-linux < %s -codegenprepare -S | FileCheck -check-prefix=NONEON %s
+
+define <8 x i16> @sink_zext(<8 x i8> %a, <8 x i8> %b, i1 %c) {
+; NEON-LABEL: @sink_zext(
+; NEON-NEXT:  entry:
+; NEON-NEXT:    br i1 [[C:%.*]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
+; NEON:       if.then:
+; NEON-NEXT:    [[ZB_1:%.*]] = zext <8 x i8> [[B:%.*]] to <8 x i16>
+; NEON-NEXT:    [[TMP0:%.*]] = zext <8 x i8> [[A:%.*]] to <8 x i16>
+; NEON-NEXT:    [[RES_1:%.*]] = add <8 x i16> [[TMP0]], [[ZB_1]]
+; NEON-NEXT:    ret <8 x i16> [[RES_1]]
+; NEON:       if.else:
+; NEON-NEXT:    [[ZB_2:%.*]] = zext <8 x i8> [[B]] to <8 x i16>
+; NEON-NEXT:    [[TMP1:%.*]] = zext <8 x i8> [[A]] to <8 x i16>
+; NEON-NEXT:    [[RES_2:%.*]] = sub <8 x i16> [[TMP1]], [[ZB_2]]
+; NEON-NEXT:    ret <8 x i16> [[RES_2]]
+;
+; NONEON-LABEL: @sink_zext(
+; NONEON-NEXT:  entry:
+; NONEON-NEXT:    [[ZA:%.*]] = zext <8 x i8> [[A:%.*]] to <8 x i16>
+; NONEON-NEXT:    br i1 [[C:%.*]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
+; NONEON:       if.then:
+; NONEON-NEXT:    [[ZB_1:%.*]] = zext <8 x i8> [[B:%.*]] to <8 x i16>
+; NONEON-NEXT:    [[RES_1:%.*]] = add <8 x i16> [[ZA]], [[ZB_1]]
+; NONEON-NEXT:    ret <8 x i16> [[RES_1]]
+; NONEON:       if.else:
+; NONEON-NEXT:    [[ZB_2:%.*]] = zext <8 x i8> [[B]] to <8 x i16>
+; NONEON-NEXT:    [[RES_2:%.*]] = sub <8 x i16> [[ZA]], [[ZB_2]]
+; NONEON-NEXT:    ret <8 x i16> [[RES_2]]
+;
+entry:
+  %za = zext <8 x i8> %a to <8 x i16>
+  br i1 %c, label %if.then, label %if.else
+
+if.then:
+  %zb.1 = zext <8 x i8> %b to <8 x i16>
+  %res.1 = add <8 x i16> %za, %zb.1
+  ret <8 x i16> %res.1
+
+if.else:
+  %zb.2 = zext <8 x i8> %b to <8 x i16>
+  %res.2 = sub <8 x i16> %za, %zb.2
+  ret <8 x i16> %res.2
+}
+
+define <8 x i16> @sink_sext(<8 x i8> %a, <8 x i8> %b, i1 %c) {
+; NEON-LABEL: @sink_sext(
+; NEON-NEXT:  entry:
+; NEON-NEXT:    br i1 [[C:%.*]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
+; NEON:       if.then:
+; NEON-NEXT:    [[ZB_1:%.*]] = sext <8 x i8> [[B:%.*]] to <8 x i16>
+; NEON-NEXT:    [[TMP0:%.*]] = sext <8 x i8> [[A:%.*]] to <8 x i16>
+; NEON-NEXT:    [[RES_1:%.*]] = add <8 x i16> [[TMP0]], [[ZB_1]]
+; NEON-NEXT:    ret <8 x i16> [[RES_1]]
+; NEON:       if.else:
+; NEON-NEXT:    [[ZB_2:%.*]] = sext <8 x i8> [[B]] to <8 x i16>
+; NEON-NEXT:    [[TMP1:%.*]] = sext <8 x i8> [[A]] to <8 x i16>
+; NEON-NEXT:    [[RES_2:%.*]] = sub <8 x i16> [[TMP1]], [[ZB_2]]
+; NEON-NEXT:    ret <8 x i16> [[RES_2]]
+;
+; NONEON-LABEL: @sink_sext(
+; NONEON-NEXT:  entry:
+; NONEON-NEXT:    [[ZA:%.*]] = sext <8 x i8> [[A:%.*]] to <8 x i16>
+; NONEON-NEXT:    br i1 [[C:%.*]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
+; NONEON:       if.then:
+; NONEON-NEXT:    [[ZB_1:%.*]] = sext <8 x i8> [[B:%.*]] to <8 x i16>
+; NONEON-NEXT:    [[RES_1:%.*]] = add <8 x i16> [[ZA]], [[ZB_1]]
+; NONEON-NEXT:    ret <8 x i16> [[RES_1]]
+; NONEON:       if.else:
+; NONEON-NEXT:    [[ZB_2:%.*]] = sext <8 x i8> [[B]] to <8 x i16>
+; NONEON-NEXT:    [[RES_2:%.*]] = sub <8 x i16> [[ZA]], [[ZB_2]]
+; NONEON-NEXT:    ret <8 x i16> [[RES_2]]
+;
+entry:
+  %za = sext <8 x i8> %a to <8 x i16>
+  br i1 %c, label %if.then, label %if.else
+
+if.then:
+  %zb.1 = sext <8 x i8> %b to <8 x i16>
+  %res.1 = add <8 x i16> %za, %zb.1
+  ret <8 x i16> %res.1
+
+if.else:
+  %zb.2 = sext <8 x i8> %b to <8 x i16>
+  %res.2 = sub <8 x i16> %za, %zb.2
+  ret <8 x i16> %res.2
+}
+
+define <8 x i16> @do_not_sink_nonfree_zext(<8 x i8> %a, <8 x i16> %b, i1 %c) {
+;
+; NEON-LABEL: @do_not_sink_nonfree_zext(
+; NEON-NEXT:  entry:
+; NEON-NEXT:    [[ZA:%.*]] = zext <8 x i8> [[A:%.*]] to <8 x i16>
+; NEON-NEXT:    br i1 [[C:%.*]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
+; NEON:       if.then:
+; NEON-NEXT:    [[RES_1:%.*]] = add <8 x i16> [[ZA]], [[B:%.*]]
+; NEON-NEXT:    ret <8 x i16> [[RES_1]]
+; NEON:       if.else:
+; NEON-NEXT:    ret <8 x i16> [[B]]
+;
+; NONEON-LABEL: @do_not_sink_nonfree_zext(
+; NONEON-NEXT:  entry:
+; NONEON-NEXT:    [[ZA:%.*]] = zext <8 x i8> [[A:%.*]] to <8 x i16>
+; NONEON-NEXT:    br i1 [[C:%.*]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
+; NONEON:       if.then:
+; NONEON-NEXT:    [[RES_1:%.*]] = add <8 x i16> [[ZA]], [[B:%.*]]
+; NONEON-NEXT:    ret <8 x i16> [[RES_1]]
+; NONEON:       if.else:
+; NONEON-NEXT:    ret <8 x i16> [[B]]
+;
+entry:
+  %za = zext <8 x i8> %a to <8 x i16>
+  br i1 %c, label %if.then, label %if.else
+
+if.then:
+  %res.1 = add <8 x i16> %za, %b
+  ret <8 x i16> %res.1
+
+if.else:
+  ret <8 x i16> %b
+}
+
+define <8 x i16> @do_not_sink_nonfree_sext(<8 x i8> %a, <8 x i16> %b, i1 %c) {
+; CHECK-LABEL: @do_not_sink_nonfree_sext(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br i1 [[C:%.*]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
+; CHECK:       if.then:
+; CHECK-NEXT:    [[ZB_1:%.*]] = sext <8 x i8> [[B:%.*]] to <8 x i16>
+; CHECK-NEXT:    [[TMP0:%.*]] = sext <8 x i8> [[A:%.*]] to <8 x i16>
+; CHECK-NEXT:    [[RES_1:%.*]] = add <8 x i16> [[TMP0]], [[ZB_1]]
+; CHECK-NEXT:    ret <8 x i16> [[RES_1]]
+; CHECK:       if.else:
+; CHECK-NEXT:    [[ZB_2:%.*]] = sext <8 x i8> [[B]] to <8 x i16>
+; CHECK-NEXT:    ret <8 x i16> [[ZB_2]]
+;
+; NEON-LABEL: @do_not_sink_nonfree_sext(
+; NEON-NEXT:  entry:
+; NEON-NEXT:    [[ZA:%.*]] = sext <8 x i8> [[A:%.*]] to <8 x i16>
+; NEON-NEXT:    br i1 [[C:%.*]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
+; NEON:       if.then:
+; NEON-NEXT:    [[RES_1:%.*]] = add <8 x i16> [[ZA]], [[B:%.*]]
+; NEON-NEXT:    ret <8 x i16> [[RES_1]]
+; NEON:       if.else:
+; NEON-NEXT:    ret <8 x i16> [[B]]
+;
+; NONEON-LABEL: @do_not_sink_nonfree_sext(
+; NONEON-NEXT:  entry:
+; NONEON-NEXT:    [[ZA:%.*]] = sext <8 x i8> [[A:%.*]] to <8 x i16>
+; NONEON-NEXT:    br i1 [[C:%.*]], label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
+; NONEON:       if.then:
+; NONEON-NEXT:    [[RES_1:%.*]] = add <8 x i16> [[ZA]], [[B:%.*]]
+; NONEON-NEXT:    ret <8 x i16> [[RES_1]]
+; NONEON:       if.else:
+; NONEON-NEXT:    ret <8 x i16> [[B]]
+;
+entry:
+  %za = sext <8 x i8> %a to <8 x i16>
+  br i1 %c, label %if.then, label %if.else
+
+if.then:
+  %res.1 = add <8 x i16> %za, %b
+  ret <8 x i16> %res.1
+
+if.else:
+  ret <8 x i16> %b
+}
+
+declare void @user1(<8 x i16>)
+
+; Exts can be sunk.
+define <8 x i16> @sink_shufflevector_ext_subadd_multiuse(<16 x i8> %a, <16 x i8> %b) {
+; NEON-LABEL: @sink_shufflevector_ext_subadd_multiuse(
+; NEON-NEXT:  entry:
+; NEON-NEXT:    [[S1:%.*]] = shufflevector <16 x i8> [[A:%.*]], <16 x i8> undef, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
+; NEON-NEXT:    [[S3:%.*]] = shufflevector <16 x i8> [[A]], <16 x i8> undef, <8 x i32> <i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15>
+; NEON-NEXT:    [[Z3:%.*]] = sext <8 x i8> [[S3]] to <8 x i16>
+; NEON-NEXT:    call void @user1(<8 x i16> [[Z3]])
+; NEON-NEXT:    br i1 undef, label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
+; NEON:       if.then:
+; NEON-NEXT:    [[S2:%.*]] = shufflevector <16 x i8> [[B:%.*]], <16 x i8> undef, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
+; NEON-NEXT:    [[Z2:%.*]] = zext <8 x i8> [[S2]] to <8 x i16>
+; NEON-NEXT:    [[TMP0:%.*]] = zext <8 x i8> [[S1]] to <8 x i16>
+; NEON-NEXT:    [[RES1:%.*]] = add <8 x i16> [[TMP0]], [[Z2]]
+; NEON-NEXT:    ret <8 x i16> [[RES1]]
+; NEON:       if.else:
+; NEON-NEXT:    [[S4:%.*]] = shufflevector <16 x i8> [[B]], <16 x i8> undef, <8 x i32> <i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15>
+; NEON-NEXT:    [[Z4:%.*]] = sext <8 x i8> [[S4]] to <8 x i16>
+; NEON-NEXT:    [[TMP1:%.*]] = sext <8 x i8> [[S3]] to <8 x i16>
+; NEON-NEXT:    [[RES2:%.*]] = sub <8 x i16> [[TMP1]], [[Z4]]
+; NEON-NEXT:    ret <8 x i16> [[RES2]]
+;
+; NONEON-LABEL: @sink_shufflevector_ext_subadd_multiuse(
+; NONEON-NEXT:  entry:
+; NONEON-NEXT:    [[S1:%.*]] = shufflevector <16 x i8> [[A:%.*]], <16 x i8> undef, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
+; NONEON-NEXT:    [[Z1:%.*]] = zext <8 x i8> [[S1]] to <8 x i16>
+; NONEON-NEXT:    [[S3:%.*]] = shufflevector <16 x i8> [[A]], <16 x i8> undef, <8 x i32> <i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15>
+; NONEON-NEXT:    [[Z3:%.*]] = sext <8 x i8> [[S3]] to <8 x i16>
+; NONEON-NEXT:    call void @user1(<8 x i16> [[Z3]])
+; NONEON-NEXT:    br i1 undef, label [[IF_THEN:%.*]], label [[IF_ELSE:%.*]]
+; NONEON:       if.then:
+; NONEON-NEXT:    [[S2:%.*]] = shufflevector <16 x i8> [[B:%.*]], <16 x i8> undef, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
+; NONEON-NEXT:    [[Z2:%.*]] = zext <8 x i8> [[S2]] to <8 x i16>
+; NONEON-NEXT:    [[RES1:%.*]] = add <8 x i16> [[Z1]], [[Z2]]
+; NONEON-NEXT:    ret <8 x i16> [[RES1]]
+; NONEON:       if.else:
+; NONEON-NEXT:    [[S4:%.*]] = shufflevector <16 x i8> [[B]], <16 x i8> undef, <8 x i32> <i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15>
+; NONEON-NEXT:    [[Z4:%.*]] = sext <8 x i8> [[S4]] to <8 x i16>
+; NONEON-NEXT:    [[RES2:%.*]] = sub <8 x i16> [[Z3]], [[Z4]]
+; NONEON-NEXT:    ret <8 x i16> [[RES2]]
+;
+entry:
+  %s1 = shufflevector <16 x i8> %a, <16 x i8> undef, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
+  %z1 = zext <8 x i8> %s1 to <8 x i16>
+  %s3 = shufflevector <16 x i8> %a, <16 x i8> undef, <8 x i32> <i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15>
+  %z3 = sext <8 x i8> %s3 to <8 x i16>
+  call void @user1(<8 x i16> %z3)
+  br i1 undef, label %if.then, label %if.else
+
+if.then:
+  %s2 = shufflevector <16 x i8> %b, <16 x i8> undef, <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7>
+  %z2 = zext <8 x i8> %s2 to <8 x i16>
+  %res1 = add <8 x i16> %z1, %z2
+  ret <8 x i16> %res1
+
+if.else:
+  %s4 = shufflevector <16 x i8> %b, <16 x i8> undef, <8 x i32> <i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15>
+  %z4 = sext <8 x i8> %s4 to <8 x i16>
+  %res2 = sub <8 x i16> %z3, %z4
+  ret <8 x i16> %res2
+}