Index: lib/Target/ARM/ARMParallelDSP.cpp
===================================================================
--- lib/Target/ARM/ARMParallelDSP.cpp
+++ lib/Target/ARM/ARMParallelDSP.cpp
@@ -127,6 +127,16 @@
     bool InsertAcc(Value *V) {
       if (Acc)
         return false;
+
+      // May have discovered the incoming accumulator value via a sext.
+      if (V->getType() != Root->getType()) {
+        assert(is64Bit() && "expected 64-bit result");
+
+        IRBuilder<NoFolder> Builder(Root->getParent(),
+                                    BasicBlock::iterator(Root));
+        V = Builder.CreateSExt(V, Root->getType());
+      }
+
       Acc = V;
       return true;
     }
Index: test/CodeGen/ARM/ParallelDSP/blocks.ll
===================================================================
--- test/CodeGen/ARM/ParallelDSP/blocks.ll
+++ test/CodeGen/ARM/ParallelDSP/blocks.ll
@@ -1,4 +1,4 @@
-; RUN: opt -arm-parallel-dsp -mtriple=armv7-a -S %s -o - | FileCheck %s
+; RUN: opt -arm-parallel-dsp -dce -mtriple=armv7-a -S %s -o - | FileCheck %s
 
 ; CHECK-LABEL: single_block
 ; CHECK: [[CAST_A:%[^ ]+]] = bitcast i16* %a to i32*
Index: test/CodeGen/ARM/ParallelDSP/sext-acc.ll
===================================================================
--- /dev/null
+++ test/CodeGen/ARM/ParallelDSP/sext-acc.ll
@@ -0,0 +1,186 @@
+; RUN: opt -arm-parallel-dsp -dce -mtriple=armv7-a -S %s -o - | FileCheck %s
+
+; CHECK-LABEL: sext_acc_1
+; CHECK: [[CAST_A:%[^ ]+]] = bitcast i16* %a to i32*
+; CHECK: [[A:%[^ ]+]] = load i32, i32* [[CAST_A]]
+; CHECK: [[CAST_B:%[^ ]+]] = bitcast i16* %b to i32*
+; CHECK: [[B:%[^ ]+]] = load i32, i32* [[CAST_B]]
+; CHECK: [[ACC:%[^ ]+]] = sext i32 %acc to i64
+; CHECK: call i64 @llvm.arm.smlald(i32 [[A]], i32 [[B]], i64 [[ACC]])
+define i64 @sext_acc_1(i16* %a, i16* %b, i32 %acc) {
+entry:
+  %ld.a.0 = load i16, i16* %a
+  %sext.a.0 = sext i16 %ld.a.0 to i32
+  %ld.b.0 = load i16, i16* %b
+  %sext.b.0 = sext i16 %ld.b.0 to i32
+  %mul.0 = mul i32 %sext.a.0, %sext.b.0
+  %addr.a.1 = getelementptr i16, i16* %a, i32 1
+  %addr.b.1 = getelementptr i16, i16* %b, i32 1
+  %ld.a.1 = load i16, i16* %addr.a.1
+  %sext.a.1 = sext i16 %ld.a.1 to i32
+  %ld.b.1 = load i16, i16* %addr.b.1
+  %sext.b.1 = sext i16 %ld.b.1 to i32
+  %mul.1 = mul i32 %sext.a.1, %sext.b.1
+  %sext.mul.0 = sext i32 %mul.0 to i64
+  %sext.mul.1 = sext i32 %mul.1 to i64
+  %add = add i64 %sext.mul.0, %sext.mul.1
+  %sext.acc = sext i32 %acc to i64
+  %res = add i64 %add, %sext.acc
+  ret i64 %res
+}
+
+; CHECK-LABEL: sext_acc_2
+; CHECK: [[CAST_A:%[^ ]+]] = bitcast i16* %a to i32*
+; CHECK: [[A:%[^ ]+]] = load i32, i32* [[CAST_A]]
+; CHECK: [[CAST_B:%[^ ]+]] = bitcast i16* %b to i32*
+; CHECK: [[B:%[^ ]+]] = load i32, i32* [[CAST_B]]
+; CHECK: [[CAST_A_2:%[^ ]+]] = bitcast i16* %addr.a.2 to i32*
+; CHECK: [[A_2:%[^ ]+]] = load i32, i32* %4
+; CHECK: [[CAST_B_2:%[^ ]+]] = bitcast i16* %addr.b.2 to i32*
+; CHECK: [[B_2:%[^ ]+]] = load i32, i32* %6
+; CHECK: [[ACC:%[^ ]+]] = sext i32 %acc to i64
+; CHECK: [[SMLALD:%[^ ]+]] = call i64 @llvm.arm.smlald(i32 [[A]], i32 [[B]], i64 [[ACC]])
+; CHECK: call i64 @llvm.arm.smlald(i32 [[A_2]], i32 [[B_2]], i64 [[SMLALD]])
+define i64 @sext_acc_2(i16* %a, i16* %b, i32 %acc) {
+entry:
+  %ld.a.0 = load i16, i16* %a
+  %sext.a.0 = sext i16 %ld.a.0 to i32
+  %ld.b.0 = load i16, i16* %b
+  %sext.b.0 = sext i16 %ld.b.0 to i32
+  %mul.0 = mul i32 %sext.a.0, %sext.b.0
+  %addr.a.1 = getelementptr i16, i16* %a, i32 1
+  %addr.b.1 = getelementptr i16, i16* %b, i32 1
+  %ld.a.1 = load i16, i16* %addr.a.1
+  %sext.a.1 = sext i16 %ld.a.1 to i32
+  %ld.b.1 = load i16, i16* %addr.b.1
+  %sext.b.1 = sext i16 %ld.b.1 to i32
+  %mul.1 = mul i32 %sext.a.1, %sext.b.1
+  %sext.mul.0 = sext i32 %mul.0 to i64
+  %sext.mul.1 = sext i32 %mul.1 to i64
+  %add = add i64 %sext.mul.0, %sext.mul.1
+  %sext.acc = sext i32 %acc to i64
+  %add.1 = add i64 %add, %sext.acc
+  %addr.a.2 = getelementptr i16, i16* %a, i32 2
+  %addr.b.2 = getelementptr i16, i16* %b, i32 2
+  %ld.a.2 = load i16, i16* %addr.a.2
+  %sext.a.2 = sext i16 %ld.a.2 to i32
+  %ld.b.2 = load i16, i16* %addr.b.2
+  %sext.b.2 = sext i16 %ld.b.2 to i32
+  %mul.2 = mul i32 %sext.a.2, %sext.b.2
+  %sext.mul.2 = sext i32 %mul.2 to i64
+  %addr.a.3 = getelementptr i16, i16* %a, i32 3
+  %addr.b.3 = getelementptr i16, i16* %b, i32 3
+  %ld.a.3 = load i16, i16* %addr.a.3
+  %sext.a.3 = sext i16 %ld.a.3 to i32
+  %ld.b.3 = load i16, i16* %addr.b.3
+  %sext.b.3 = sext i16 %ld.b.3 to i32
+  %mul.3 = mul i32 %sext.a.3, %sext.b.3
+  %sext.mul.3 = sext i32 %mul.3 to i64
+  %add.2 = add i64 %sext.mul.2, %sext.mul.3
+  %add.3 = add i64 %add.1, %add.2
+  ret i64 %add.3
+}
+
+; CHECK-LABEL: sext_acc_3
+; CHECK: [[CAST_A:%[^ ]+]] = bitcast i16* %a to i32*
+; CHECK: [[A:%[^ ]+]] = load i32, i32* [[CAST_A]]
+; CHECK: [[CAST_B:%[^ ]+]] = bitcast i16* %b to i32*
+; CHECK: [[B:%[^ ]+]] = load i32, i32* [[CAST_B]]
+; CHECK: [[CAST_A_2:%[^ ]+]] = bitcast i16* %addr.a.2 to i32*
+; CHECK: [[A_2:%[^ ]+]] = load i32, i32* %4
+; CHECK: [[CAST_B_2:%[^ ]+]] = bitcast i16* %addr.b.2 to i32*
+; CHECK: [[B_2:%[^ ]+]] = load i32, i32* %6
+; CHECK: [[ACC:%[^ ]+]] = sext i32 %acc to i64
+; CHECK: [[SMLALD:%[^ ]+]] = call i64 @llvm.arm.smlald(i32 [[A]], i32 [[B]], i64 [[ACC]])
+; CHECK: call i64 @llvm.arm.smlald(i32 [[A_2]], i32 [[B_2]], i64 [[SMLALD]])
+define i64 @sext_acc_3(i16* %a, i16* %b, i32 %acc) {
+entry:
+  %ld.a.0 = load i16, i16* %a
+  %sext.a.0 = sext i16 %ld.a.0 to i32
+  %ld.b.0 = load i16, i16* %b
+  %sext.b.0 = sext i16 %ld.b.0 to i32
+  %mul.0 = mul i32 %sext.a.0, %sext.b.0
+  %addr.a.1 = getelementptr i16, i16* %a, i32 1
+  %addr.b.1 = getelementptr i16, i16* %b, i32 1
+  %ld.a.1 = load i16, i16* %addr.a.1
+  %sext.a.1 = sext i16 %ld.a.1 to i32
+  %ld.b.1 = load i16, i16* %addr.b.1
+  %sext.b.1 = sext i16 %ld.b.1 to i32
+  %mul.1 = mul i32 %sext.a.1, %sext.b.1
+  %sext.mul.0 = sext i32 %mul.0 to i64
+  %sext.mul.1 = sext i32 %mul.1 to i64
+  %add = add i64 %sext.mul.0, %sext.mul.1
+  %addr.a.2 = getelementptr i16, i16* %a, i32 2
+  %addr.b.2 = getelementptr i16, i16* %b, i32 2
+  %ld.a.2 = load i16, i16* %addr.a.2
+  %sext.a.2 = sext i16 %ld.a.2 to i32
+  %ld.b.2 = load i16, i16* %addr.b.2
+  %sext.b.2 = sext i16 %ld.b.2 to i32
+  %mul.2 = mul i32 %sext.a.2, %sext.b.2
+  %sext.mul.2 = sext i32 %mul.2 to i64
+  %addr.a.3 = getelementptr i16, i16* %a, i32 3
+  %addr.b.3 = getelementptr i16, i16* %b, i32 3
+  %ld.a.3 = load i16, i16* %addr.a.3
+  %sext.a.3 = sext i16 %ld.a.3 to i32
+  %ld.b.3 = load i16, i16* %addr.b.3
+  %sext.b.3 = sext i16 %ld.b.3 to i32
+  %mul.3 = mul i32 %sext.a.3, %sext.b.3
+  %sext.mul.3 = sext i32 %mul.3 to i64
+  %add.1 = add i64 %sext.mul.2, %sext.mul.3
+  %add.2 = add i64 %add, %add.1
+  %sext.acc = sext i32 %acc to i64
+  %add.3 = add i64 %add.2, %sext.acc
+  ret i64 %add.3
+}
+
+; CHECK-LABEL: sext_acc_4
+; CHECK: [[CAST_A:%[^ ]+]] = bitcast i16* %a to i32*
+; CHECK: [[A:%[^ ]+]] = load i32, i32* [[CAST_A]]
+; CHECK: [[CAST_B:%[^ ]+]] = bitcast i16* %b to i32*
+; CHECK: [[B:%[^ ]+]] = load i32, i32* [[CAST_B]]
+; CHECK: [[CAST_A_2:%[^ ]+]] = bitcast i16* %addr.a.2 to i32*
+; CHECK: [[A_2:%[^ ]+]] = load i32, i32* %4
+; CHECK: [[CAST_B_2:%[^ ]+]] = bitcast i16* %addr.b.2 to i32*
+; CHECK: [[B_2:%[^ ]+]] = load i32, i32* %6
+; CHECK: [[ACC:%[^ ]+]] = sext i32 %acc to i64
+; CHECK: [[SMLALD:%[^ ]+]] = call i64 @llvm.arm.smlald(i32 [[A]], i32 [[B]], i64 [[ACC]])
+; CHECK: call i64 @llvm.arm.smlald(i32 [[A_2]], i32 [[B_2]], i64 [[SMLALD]])
+define i64 @sext_acc_4(i16* %a, i16* %b, i32 %acc) {
+entry:
+  %ld.a.0 = load i16, i16* %a
+  %sext.a.0 = sext i16 %ld.a.0 to i32
+  %ld.b.0 = load i16, i16* %b
+  %sext.b.0 = sext i16 %ld.b.0 to i32
+  %mul.0 = mul i32 %sext.a.0, %sext.b.0
+  %addr.a.1 = getelementptr i16, i16* %a, i32 1
+  %addr.b.1 = getelementptr i16, i16* %b, i32 1
+  %ld.a.1 = load i16, i16* %addr.a.1
+  %sext.a.1 = sext i16 %ld.a.1 to i32
+  %ld.b.1 = load i16, i16* %addr.b.1
+  %sext.b.1 = sext i16 %ld.b.1 to i32
+  %mul.1 = mul i32 %sext.a.1, %sext.b.1
+  %add = add i32 %mul.0, %mul.1
+  %sext.add = sext i32 %add to i64
+  %addr.a.2 = getelementptr i16, i16* %a, i32 2
+  %addr.b.2 = getelementptr i16, i16* %b, i32 2
+  %ld.a.2 = load i16, i16* %addr.a.2
+  %sext.a.2 = sext i16 %ld.a.2 to i32
+  %ld.b.2 = load i16, i16* %addr.b.2
+  %sext.b.2 = sext i16 %ld.b.2 to i32
+  %mul.2 = mul i32 %sext.a.2, %sext.b.2
+  %sext.mul.2 = sext i32 %mul.2 to i64
+  %addr.a.3 = getelementptr i16, i16* %a, i32 3
+  %addr.b.3 = getelementptr i16, i16* %b, i32 3
+  %ld.a.3 = load i16, i16* %addr.a.3
+  %sext.a.3 = sext i16 %ld.a.3 to i32
+  %ld.b.3 = load i16, i16* %addr.b.3
+  %sext.b.3 = sext i16 %ld.b.3 to i32
+  %mul.3 = mul i32 %sext.a.3, %sext.b.3
+  %sext.mul.3 = sext i32 %mul.3 to i64
+  %sext.acc = sext i32 %acc to i64
+  %add.1 = add i64 %sext.mul.2, %sext.add
+  %add.2 = add i64 %sext.add, %add.1
+  %add.3 = add i64 %add.2, %sext.mul.3
+  %add.4 = add i64 %add.3, %sext.acc
+  ret i64 %add.4
+}