Index: llvm/trunk/lib/Target/X86/X86InstrInfo.cpp
===================================================================
--- llvm/trunk/lib/Target/X86/X86InstrInfo.cpp
+++ llvm/trunk/lib/Target/X86/X86InstrInfo.cpp
@@ -5295,21 +5295,57 @@
                                Size, Alignment, /*AllowCommute=*/true);
 }
 
-static bool isPartialRegisterLoad(const MachineInstr &LoadMI,
-                                  const MachineFunction &MF) {
+/// Check if \p LoadMI is a partial register load that we can't fold into \p MI
+/// because the latter uses contents that wouldn't be defined in the folded
+/// version.  For instance, this transformation isn't legal:
+///   movss (%rdi), %xmm0
+///   addps %xmm0, %xmm0
+/// ->
+///   addps (%rdi), %xmm0
+///
+/// But this one is:
+///   movss (%rdi), %xmm0
+///   addss %xmm0, %xmm0
+/// ->
+///   addss (%rdi), %xmm0
+///
+static bool isNonFoldablePartialRegisterLoad(const MachineInstr &LoadMI,
+                                             const MachineInstr &UserMI,
+                                             const MachineFunction &MF) {
   unsigned Opc = LoadMI.getOpcode();
+  unsigned UserOpc = UserMI.getOpcode();
   unsigned RegSize =
       MF.getRegInfo().getRegClass(LoadMI.getOperand(0).getReg())->getSize();
 
-  if ((Opc == X86::MOVSSrm || Opc == X86::VMOVSSrm) && RegSize > 4)
+  if ((Opc == X86::MOVSSrm || Opc == X86::VMOVSSrm) && RegSize > 4) {
     // These instructions only load 32 bits, we can't fold them if the
-    // destination register is wider than 32 bits (4 bytes).
-    return true;
+    // destination register is wider than 32 bits (4 bytes), and its user
+    // instruction isn't scalar (SS).
+    switch (UserOpc) {
+    case X86::ADDSSrr_Int: case X86::VADDSSrr_Int:
+    case X86::DIVSSrr_Int: case X86::VDIVSSrr_Int:
+    case X86::MULSSrr_Int: case X86::VMULSSrr_Int:
+    case X86::SUBSSrr_Int: case X86::VSUBSSrr_Int:
+      return false;
+    default:
+      return true;
+    }
+  }
 
-  if ((Opc == X86::MOVSDrm || Opc == X86::VMOVSDrm) && RegSize > 8)
+  if ((Opc == X86::MOVSDrm || Opc == X86::VMOVSDrm) && RegSize > 8) {
     // These instructions only load 64 bits, we can't fold them if the
-    // destination register is wider than 64 bits (8 bytes).
-    return true;
+    // destination register is wider than 64 bits (8 bytes), and its user
+    // instruction isn't scalar (SD).
+    switch (UserOpc) {
+    case X86::ADDSDrr_Int: case X86::VADDSDrr_Int:
+    case X86::DIVSDrr_Int: case X86::VDIVSDrr_Int:
+    case X86::MULSDrr_Int: case X86::VMULSDrr_Int:
+    case X86::SUBSDrr_Int: case X86::VSUBSDrr_Int:
+      return false;
+    default:
+      return true;
+    }
+  }
 
   return false;
 }
@@ -5321,7 +5357,7 @@
   unsigned NumOps = LoadMI->getDesc().getNumOperands();
   int FrameIndex;
   if (isLoadFromStackSlot(LoadMI, FrameIndex)) {
-    if (isPartialRegisterLoad(*LoadMI, MF))
+    if (isNonFoldablePartialRegisterLoad(*LoadMI, *MI, MF))
       return nullptr;
     return foldMemoryOperandImpl(MF, MI, Ops, InsertPt, FrameIndex);
   }
@@ -5434,7 +5470,7 @@
     break;
   }
   default: {
-    if (isPartialRegisterLoad(*LoadMI, MF))
+    if (isNonFoldablePartialRegisterLoad(*LoadMI, *MI, MF))
       return nullptr;
 
     // Folding a normal load. Just copy the load's address operands.
Index: llvm/trunk/test/CodeGen/X86/fold-load-binops.ll
===================================================================
--- llvm/trunk/test/CodeGen/X86/fold-load-binops.ll
+++ llvm/trunk/test/CodeGen/X86/fold-load-binops.ll
@@ -0,0 +1,142 @@
+; RUN: llc -mtriple=x86_64-unknown-unknown -mattr=+sse2 < %s | FileCheck %s --check-prefix=SSE
+; RUN: llc -mtriple=x86_64-unknown-unknown -mattr=+avx < %s | FileCheck %s --check-prefix=AVX
+
+; Verify that we're folding the load into the math instruction.
+; This pattern is generated out of the simplest intrinsics usage:
+;  _mm_add_ss(a, _mm_load_ss(b));
+
+define <4 x float> @addss(<4 x float> %va, float* %pb) {
+; SSE-LABEL: addss:
+; SSE:       # BB#0:
+; SSE-NEXT:    addss (%rdi), %xmm0
+; SSE-NEXT:    retq
+;
+; AVX-LABEL: addss:
+; AVX:       # BB#0:
+; AVX-NEXT:    vaddss (%rdi), %xmm0, %xmm0
+; AVX-NEXT:    retq
+    %a = extractelement <4 x float> %va, i32 0
+    %b = load float, float* %pb
+    %r = fadd float %a, %b
+    %vr = insertelement <4 x float> %va, float %r, i32 0
+    ret <4 x float> %vr
+}
+
+define <2 x double> @addsd(<2 x double> %va, double* %pb) {
+; SSE-LABEL: addsd:
+; SSE:       # BB#0:
+; SSE-NEXT:    addsd (%rdi), %xmm0
+; SSE-NEXT:    retq
+;
+; AVX-LABEL: addsd:
+; AVX:       # BB#0:
+; AVX-NEXT:    vaddsd (%rdi), %xmm0, %xmm0
+; AVX-NEXT:    retq
+    %a = extractelement <2 x double> %va, i32 0
+    %b = load double, double* %pb
+    %r = fadd double %a, %b
+    %vr = insertelement <2 x double> %va, double %r, i32 0
+    ret <2 x double> %vr
+}
+
+define <4 x float> @subss(<4 x float> %va, float* %pb) {
+; SSE-LABEL: subss:
+; SSE:       # BB#0:
+; SSE-NEXT:    subss (%rdi), %xmm0
+; SSE-NEXT:    retq
+;
+; AVX-LABEL: subss:
+; AVX:       # BB#0:
+; AVX-NEXT:    vsubss (%rdi), %xmm0, %xmm0
+; AVX-NEXT:    retq
+    %a = extractelement <4 x float> %va, i32 0
+    %b = load float, float* %pb
+    %r = fsub float %a, %b
+    %vr = insertelement <4 x float> %va, float %r, i32 0
+    ret <4 x float> %vr
+}
+
+define <2 x double> @subsd(<2 x double> %va, double* %pb) {
+; SSE-LABEL: subsd:
+; SSE:       # BB#0:
+; SSE-NEXT:    subsd (%rdi), %xmm0
+; SSE-NEXT:    retq
+;
+; AVX-LABEL: subsd:
+; AVX:       # BB#0:
+; AVX-NEXT:    vsubsd (%rdi), %xmm0, %xmm0
+; AVX-NEXT:    retq
+    %a = extractelement <2 x double> %va, i32 0
+    %b = load double, double* %pb
+    %r = fsub double %a, %b
+    %vr = insertelement <2 x double> %va, double %r, i32 0
+    ret <2 x double> %vr
+}
+
+define <4 x float> @mulss(<4 x float> %va, float* %pb) {
+; SSE-LABEL: mulss:
+; SSE:       # BB#0:
+; SSE-NEXT:    mulss (%rdi), %xmm0
+; SSE-NEXT:    retq
+;
+; AVX-LABEL: mulss:
+; AVX:       # BB#0:
+; AVX-NEXT:    vmulss (%rdi), %xmm0, %xmm0
+; AVX-NEXT:    retq
+    %a = extractelement <4 x float> %va, i32 0
+    %b = load float, float* %pb
+    %r = fmul float %a, %b
+    %vr = insertelement <4 x float> %va, float %r, i32 0
+    ret <4 x float> %vr
+}
+
+define <2 x double> @mulsd(<2 x double> %va, double* %pb) {
+; SSE-LABEL: mulsd:
+; SSE:       # BB#0:
+; SSE-NEXT:    mulsd (%rdi), %xmm0
+; SSE-NEXT:    retq
+;
+; AVX-LABEL: mulsd:
+; AVX:       # BB#0:
+; AVX-NEXT:    vmulsd (%rdi), %xmm0, %xmm0
+; AVX-NEXT:    retq
+    %a = extractelement <2 x double> %va, i32 0
+    %b = load double, double* %pb
+    %r = fmul double %a, %b
+    %vr = insertelement <2 x double> %va, double %r, i32 0
+    ret <2 x double> %vr
+}
+
+define <4 x float> @divss(<4 x float> %va, float* %pb) {
+; SSE-LABEL: divss:
+; SSE:       # BB#0:
+; SSE-NEXT:    divss (%rdi), %xmm0
+; SSE-NEXT:    retq
+;
+; AVX-LABEL: divss:
+; AVX:       # BB#0:
+; AVX-NEXT:    vdivss (%rdi), %xmm0, %xmm0
+; AVX-NEXT:    retq
+    %a = extractelement <4 x float> %va, i32 0
+    %b = load float, float* %pb
+    %r = fdiv float %a, %b
+    %vr = insertelement <4 x float> %va, float %r, i32 0
+    ret <4 x float> %vr
+}
+
+define <2 x double> @divsd(<2 x double> %va, double* %pb) {
+; SSE-LABEL: divsd:
+; SSE:       # BB#0:
+; SSE-NEXT:    divsd (%rdi), %xmm0
+; SSE-NEXT:    retq
+;
+; AVX-LABEL: divsd:
+; AVX:       # BB#0:
+; AVX-NEXT:    vdivsd (%rdi), %xmm0, %xmm0
+; AVX-NEXT:    retq
+    %a = extractelement <2 x double> %va, i32 0
+    %b = load double, double* %pb
+    %r = fdiv double %a, %b
+    %vr = insertelement <2 x double> %va, double %r, i32 0
+    ret <2 x double> %vr
+}