Index: lib/Target/X86/X86InstrVecCompiler.td
===================================================================
--- lib/Target/X86/X86InstrVecCompiler.td
+++ lib/Target/X86/X86InstrVecCompiler.td
@@ -360,3 +360,62 @@
   defm : subvector_zero_lowering<"DQAY", VR256, v64i8, v32i8, v16i32,
                                  loadv4i64, sub_ymm>;
 }
+
+// List of opcodes that guaranteed to zero the upper elements of vector regs.
+// TODO: Ideally this would be a blacklist instead of a whitelist. But SHA
+// intrinsics and some MMX->XMM move instructions that aren't VEX encoded make
+// this difficult. So starting with a couple opcodes used by reduction loops
+// where we explicitly insert zeros.
+class veczeroupper<ValueType vt, RegisterClass RC> :
+  PatLeaf<(vt RC:$src), [{
+    return N->getOpcode() == X86ISD::VPMADDWD;
+  }]>;
+
+def zeroupperv2f64 : veczeroupper<v2f64, VR128>;
+def zeroupperv4f32 : veczeroupper<v4f32, VR128>;
+def zeroupperv2i64 : veczeroupper<v2i64, VR128>;
+def zeroupperv4i32 : veczeroupper<v4i32, VR128>;
+def zeroupperv8i16 : veczeroupper<v8i16, VR128>;
+def zeroupperv16i8 : veczeroupper<v16i8, VR128>;
+
+def zeroupperv4f64  : veczeroupper<v4f64, VR256>;
+def zeroupperv8f32  : veczeroupper<v8f32, VR256>;
+def zeroupperv4i64  : veczeroupper<v4i64, VR256>;
+def zeroupperv8i32  : veczeroupper<v8i32, VR256>;
+def zeroupperv16i16 : veczeroupper<v16i16, VR256>;
+def zeroupperv32i8  : veczeroupper<v32i8, VR256>;
+
+
+// If we can guarantee the upper elements have already been zeroed we can elide
+// an explicit zeroing.
+multiclass subvector_zero_ellision<RegisterClass RC, ValueType DstTy,
+                                   ValueType SrcTy, ValueType ZeroTy,
+                                   SubRegIndex SubIdx, PatLeaf Zeroupper> {
+  def : Pat<(DstTy (insert_subvector (bitconvert (ZeroTy immAllZerosV)),
+                                     Zeroupper:$src, (iPTR 0))),
+            (SUBREG_TO_REG (i64 0), RC:$src, SubIdx)>;
+}
+
+// 128->256
+defm: subvector_zero_ellision<VR128, v4f64,  v2f64, v8i32, sub_xmm, zeroupperv2f64>;
+defm: subvector_zero_ellision<VR128, v8f32,  v4f32, v8i32, sub_xmm, zeroupperv4f32>;
+defm: subvector_zero_ellision<VR128, v4i64,  v2i64, v8i32, sub_xmm, zeroupperv2i64>;
+defm: subvector_zero_ellision<VR128, v8i32,  v4i32, v8i32, sub_xmm, zeroupperv4i32>;
+defm: subvector_zero_ellision<VR128, v16i16, v8i16, v8i32, sub_xmm, zeroupperv8i16>;
+defm: subvector_zero_ellision<VR128, v32i8,  v16i8, v8i32, sub_xmm, zeroupperv16i8>;
+
+// 128->512
+defm: subvector_zero_ellision<VR128, v8f64,  v2f64, v16i32, sub_xmm, zeroupperv2f64>;
+defm: subvector_zero_ellision<VR128, v16f32, v4f32, v16i32, sub_xmm, zeroupperv4f32>;
+defm: subvector_zero_ellision<VR128, v8i64,  v2i64, v16i32, sub_xmm, zeroupperv2i64>;
+defm: subvector_zero_ellision<VR128, v16i32, v4i32, v16i32, sub_xmm, zeroupperv4i32>;
+defm: subvector_zero_ellision<VR128, v32i16, v8i16, v16i32, sub_xmm, zeroupperv8i16>;
+defm: subvector_zero_ellision<VR128, v64i8,  v16i8, v16i32, sub_xmm, zeroupperv16i8>;
+
+// 256->512
+defm: subvector_zero_ellision<VR256, v8f64,  v4f64,  v16i32, sub_ymm, zeroupperv4f64>;
+defm: subvector_zero_ellision<VR256, v16f32, v8f32,  v16i32, sub_ymm, zeroupperv8f32>;
+defm: subvector_zero_ellision<VR256, v8i64,  v4i64,  v16i32, sub_ymm, zeroupperv4i64>;
+defm: subvector_zero_ellision<VR256, v16i32, v8i32,  v16i32, sub_ymm, zeroupperv8i32>;
+defm: subvector_zero_ellision<VR256, v32i16, v16i16, v16i32, sub_ymm, zeroupperv16i16>;
+defm: subvector_zero_ellision<VR256, v64i8,  v32i8,  v16i32, sub_ymm, zeroupperv32i8>;
Index: test/CodeGen/X86/madd.ll
===================================================================
--- test/CodeGen/X86/madd.ll
+++ test/CodeGen/X86/madd.ll
@@ -40,7 +40,6 @@
 ; AVX2-NEXT:    # =>This Inner Loop Header: Depth=1
 ; AVX2-NEXT:    vmovdqu (%rsi,%rcx,2), %xmm1
 ; AVX2-NEXT:    vpmaddwd (%rdi,%rcx,2), %xmm1, %xmm1
-; AVX2-NEXT:    vmovdqa %xmm1, %xmm1
 ; AVX2-NEXT:    vpaddd %ymm0, %ymm1, %ymm0
 ; AVX2-NEXT:    addq $8, %rcx
 ; AVX2-NEXT:    cmpq %rcx, %rax
@@ -65,7 +64,6 @@
 ; AVX512-NEXT:    # =>This Inner Loop Header: Depth=1
 ; AVX512-NEXT:    vmovdqu (%rsi,%rcx,2), %xmm1
 ; AVX512-NEXT:    vpmaddwd (%rdi,%rcx,2), %xmm1, %xmm1
-; AVX512-NEXT:    vmovdqa %xmm1, %xmm1
 ; AVX512-NEXT:    vpaddd %ymm0, %ymm1, %ymm0
 ; AVX512-NEXT:    addq $8, %rcx
 ; AVX512-NEXT:    cmpq %rcx, %rax
@@ -314,7 +312,6 @@
 ; AVX512-NEXT:    vpmovsxbw (%rdi,%rcx), %ymm1
 ; AVX512-NEXT:    vpmovsxbw (%rsi,%rcx), %ymm2
 ; AVX512-NEXT:    vpmaddwd %ymm1, %ymm2, %ymm1
-; AVX512-NEXT:    vmovdqa %ymm1, %ymm1
 ; AVX512-NEXT:    vpaddd %zmm0, %zmm1, %zmm0
 ; AVX512-NEXT:    addq $16, %rcx
 ; AVX512-NEXT:    cmpq %rcx, %rax