diff --git a/lib/Target/X86/X86InstrFPStack.td b/lib/Target/X86/X86InstrFPStack.td
index 13b5d229d17..3c6790fc27d 100644
--- a/lib/Target/X86/X86InstrFPStack.td
+++ b/lib/Target/X86/X86InstrFPStack.td
@@ -349,7 +349,7 @@ def CMOVNP_F : FPI<0xD8, AddRegFrm, (outs RST:$op), (ins),
 let isLoad = 1 in {
 def LD_Fp32m   : FpIf32<(outs RFP32:$dst), (ins f32mem:$src), ZeroArgFP,
                   [(set RFP32:$dst, (loadf32 addr:$src))]>;
-let isReMaterializable = 1 in
+let isReMaterializable = 1, mayHaveSideEffects = 1 in
   def LD_Fp64m : FpIf64<(outs RFP64:$dst), (ins f64mem:$src), ZeroArgFP,
                   [(set RFP64:$dst, (loadf64 addr:$src))]>;
 def LD_Fp80m   : FpI_<(outs RFP80:$dst), (ins f80mem:$src), ZeroArgFP,
@@ -466,7 +466,7 @@ def ST_FPrr  : FPI<0xD8, AddRegFrm, (outs), (ins RST:$op), "fstp\t$op">, DD;
 def XCH_F    : FPI<0xC8, AddRegFrm, (outs), (ins RST:$op), "fxch\t$op">, D9;
 
 // Floating point constant loads.
-let isReMaterializable = 1 in {
+let isReMaterializable = 1, neverHasSideEffects = 1 in {
 def LD_Fp032 : FpIf32<(outs RFP32:$dst), (ins), ZeroArgFP,
                 [(set RFP32:$dst, fpimm0)]>;
 def LD_Fp132 : FpIf32<(outs RFP32:$dst), (ins), ZeroArgFP,
diff --git a/lib/Target/X86/X86InstrInfo.cpp b/lib/Target/X86/X86InstrInfo.cpp
index 9d5e6371199..d6d146f2a55 100644
--- a/lib/Target/X86/X86InstrInfo.cpp
+++ b/lib/Target/X86/X86InstrInfo.cpp
@@ -144,6 +144,40 @@ bool X86InstrInfo::isReallyTriviallyReMaterializable(MachineInstr *MI) const {
   return true;
 }
 
+/// isReallySideEffectFree - If the M_MAY_HAVE_SIDE_EFFECTS flag is set, this
+/// method is called to determine if the specific instance of this instruction
+/// has side effects. This is useful in cases of instructions, like loads, which
+/// generally always have side effects. A load from a constant pool doesn't have
+/// side effects, though. So we need to differentiate it from the general case.
+bool X86InstrInfo::isReallySideEffectFree(MachineInstr *MI) const {
+  switch (MI->getOpcode()) {
+  default: break;
+  case X86::MOV8rm:
+  case X86::MOV16rm:
+  case X86::MOV16_rm:
+  case X86::MOV32rm:
+  case X86::MOV32_rm:
+  case X86::MOV64rm:
+  case X86::LD_Fp64m:
+  case X86::MOVSSrm:
+  case X86::MOVSDrm:
+  case X86::MOVAPSrm:
+  case X86::MOVAPDrm:
+  case X86::MMX_MOVD64rm:
+  case X86::MMX_MOVQ64rm:
+    // Loads from constant pools have no side effects
+    return MI->getOperand(1).isRegister() && MI->getOperand(2).isImmediate() &&
+           MI->getOperand(3).isRegister() && MI->getOperand(4).isConstantPoolIndex() &&
+           MI->getOperand(1).getReg() == 0 &&
+           MI->getOperand(2).getImmedValue() == 1 &&
+           MI->getOperand(3).getReg() == 0;
+  }
+
+  // All other instances of these instructions are presumed to have side
+  // effects.
+  return false;
+}
+
 /// hasLiveCondCodeDef - True if MI has a condition code def, e.g. EFLAGS, that
 /// is not marked dead.
 static bool hasLiveCondCodeDef(MachineInstr *MI) {
diff --git a/lib/Target/X86/X86InstrInfo.h b/lib/Target/X86/X86InstrInfo.h
index 2694481caab..02d25c73c77 100644
--- a/lib/Target/X86/X86InstrInfo.h
+++ b/lib/Target/X86/X86InstrInfo.h
@@ -240,7 +240,8 @@ public:
   unsigned isLoadFromStackSlot(MachineInstr *MI, int &FrameIndex) const;
   unsigned isStoreToStackSlot(MachineInstr *MI, int &FrameIndex) const;
   bool isReallyTriviallyReMaterializable(MachineInstr *MI) const;
-  
+  bool isReallySideEffectFree(MachineInstr *MI) const;
+
   /// convertToThreeAddress - This method must be implemented by targets that
   /// set the M_CONVERTIBLE_TO_3_ADDR flag.  When this flag is set, the target
   /// may be able to convert a two-address instruction into a true
diff --git a/lib/Target/X86/X86InstrInfo.td b/lib/Target/X86/X86InstrInfo.td
index e41ef7a6041..f3b51dc127d 100644
--- a/lib/Target/X86/X86InstrInfo.td
+++ b/lib/Target/X86/X86InstrInfo.td
@@ -563,7 +563,7 @@ def MOV16rr : I<0x89, MRMDestReg, (outs GR16:$dst), (ins GR16:$src),
                 "mov{w}\t{$src, $dst|$dst, $src}", []>, OpSize;
 def MOV32rr : I<0x89, MRMDestReg, (outs GR32:$dst), (ins GR32:$src),
                 "mov{l}\t{$src, $dst|$dst, $src}", []>;
-let isReMaterializable = 1 in {
+let isReMaterializable = 1, neverHasSideEffects = 1 in {
 def MOV8ri  : Ii8 <0xB0, AddRegFrm, (outs GR8 :$dst), (ins i8imm :$src),
                    "mov{b}\t{$src, $dst|$dst, $src}",
                    [(set GR8:$dst, imm:$src)]>;
@@ -584,7 +584,7 @@ def MOV32mi : Ii32<0xC7, MRM0m, (outs), (ins i32mem:$dst, i32imm:$src),
                    "mov{l}\t{$src, $dst|$dst, $src}",
                    [(store (i32 imm:$src), addr:$dst)]>;
 
-let isLoad = 1 in {
+let isLoad = 1, isReMaterializable = 1, mayHaveSideEffects = 1 in {
 def MOV8rm  : I<0x8A, MRMSrcMem, (outs GR8 :$dst), (ins i8mem :$src),
                 "mov{b}\t{$src, $dst|$dst, $src}",
                 [(set GR8:$dst, (load addr:$src))]>;
@@ -2463,7 +2463,7 @@ def CDQ : I<0x99, RawFrm, (outs), (ins),
 
 // Alias instructions that map movr0 to xor.
 // FIXME: remove when we can teach regalloc that xor reg, reg is ok.
-let Defs = [EFLAGS], isReMaterializable = 1 in {
+let Defs = [EFLAGS], isReMaterializable = 1, neverHasSideEffects = 1 in {
 def MOV8r0   : I<0x30, MRMInitReg, (outs GR8 :$dst), (ins),
                  "xor{b}\t$dst, $dst",
                  [(set GR8:$dst, 0)]>;
@@ -2486,7 +2486,7 @@ def MOV16_rr : I<0x89, MRMDestReg, (outs GR16_:$dst), (ins GR16_:$src),
                 "mov{w}\t{$src, $dst|$dst, $src}", []>, OpSize;
 def MOV32_rr : I<0x89, MRMDestReg, (outs GR32_:$dst), (ins GR32_:$src),
                 "mov{l}\t{$src, $dst|$dst, $src}", []>;
-let isLoad = 1 in {
+let isLoad = 1, isReMaterializable = 1, mayHaveSideEffects = 1 in {
 def MOV16_rm : I<0x8B, MRMSrcMem, (outs GR16_:$dst), (ins i16mem:$src),
                 "mov{w}\t{$src, $dst|$dst, $src}", []>, OpSize;
 def MOV32_rm : I<0x8B, MRMSrcMem, (outs GR32_:$dst), (ins i32mem:$src),
diff --git a/lib/Target/X86/X86InstrMMX.td b/lib/Target/X86/X86InstrMMX.td
index 08fa0dfe984..09ba4c9c0a5 100644
--- a/lib/Target/X86/X86InstrMMX.td
+++ b/lib/Target/X86/X86InstrMMX.td
@@ -158,7 +158,7 @@ def MMX_FEMMS : MMXI<0x0E, RawFrm, (outs), (ins), "femms", [(int_x86_mmx_femms)]
 // Data Transfer Instructions
 def MMX_MOVD64rr : MMXI<0x6E, MRMSrcReg, (outs VR64:$dst), (ins GR32:$src),
                         "movd\t{$src, $dst|$dst, $src}", []>;
-let isLoad = 1, isReMaterializable = 1 in
+let isLoad = 1, isReMaterializable = 1, mayHaveSideEffects = 1 in
 def MMX_MOVD64rm : MMXI<0x6E, MRMSrcMem, (outs VR64:$dst), (ins i32mem:$src),
                         "movd\t{$src, $dst|$dst, $src}", []>;
 def MMX_MOVD64mr : MMXI<0x7E, MRMDestMem, (outs), (ins i32mem:$dst, VR64:$src),
@@ -169,7 +169,7 @@ def MMX_MOVD64to64rr : MMXRI<0x6E, MRMSrcReg, (outs VR64:$dst), (ins GR64:$src),
 
 def MMX_MOVQ64rr : MMXI<0x6F, MRMSrcReg, (outs VR64:$dst), (ins VR64:$src),
                         "movq\t{$src, $dst|$dst, $src}", []>;
-let isLoad = 1, isReMaterializable = 1 in
+let isLoad = 1, isReMaterializable = 1, mayHaveSideEffects = 1 in
 def MMX_MOVQ64rm : MMXI<0x6F, MRMSrcMem, (outs VR64:$dst), (ins i64mem:$src),
                         "movq\t{$src, $dst|$dst, $src}",
                         [(set VR64:$dst, (load_mmx addr:$src))]>;
@@ -487,7 +487,7 @@ def MMX_MASKMOVQ : MMXI<0xF7, MRMDestMem, (outs), (ins VR64:$src, VR64:$mask),
 //===----------------------------------------------------------------------===//
 
 // Alias instructions that map zero vector to pxor.
-let isReMaterializable = 1 in {
+let isReMaterializable = 1, neverHasSideEffects = 1 in {
   def MMX_V_SET0       : MMXI<0xEF, MRMInitReg, (outs VR64:$dst), (ins),
                               "pxor\t$dst, $dst",
                               [(set VR64:$dst, (v2i32 immAllZerosV))]>;
diff --git a/lib/Target/X86/X86InstrSSE.td b/lib/Target/X86/X86InstrSSE.td
index a4e76b3ce1e..d6a77a2e3bf 100644
--- a/lib/Target/X86/X86InstrSSE.td
+++ b/lib/Target/X86/X86InstrSSE.td
@@ -301,7 +301,7 @@ let Uses = [EFLAGS], usesCustomDAGSchedInserter = 1 in {
 // Move Instructions
 def MOVSSrr : SSI<0x10, MRMSrcReg, (outs FR32:$dst), (ins FR32:$src),
                   "movss\t{$src, $dst|$dst, $src}", []>;
-let isLoad = 1, isReMaterializable = 1 in
+let isLoad = 1, isReMaterializable = 1, mayHaveSideEffects = 1 in
 def MOVSSrm : SSI<0x10, MRMSrcMem, (outs FR32:$dst), (ins f32mem:$src),
                   "movss\t{$src, $dst|$dst, $src}",
                   [(set FR32:$dst, (loadf32 addr:$src))]>;
@@ -445,7 +445,7 @@ def Int_COMISSrm: PSI<0x2F, MRMSrcMem, (outs),
 // start with 'Fs'.
 
 // Alias instructions that map fld0 to pxor for sse.
-let isReMaterializable = 1 in
+let isReMaterializable = 1, neverHasSideEffects = 1 in
 def FsFLD0SS : I<0xEF, MRMInitReg, (outs FR32:$dst), (ins),
                  "pxor\t$dst, $dst", [(set FR32:$dst, fp32imm0)]>,
                Requires<[HasSSE1]>, TB, OpSize;
@@ -634,7 +634,7 @@ defm MIN : sse1_fp_binop_rm<0x5D, "min", X86fmin,
 // Move Instructions
 def MOVAPSrr : PSI<0x28, MRMSrcReg, (outs VR128:$dst), (ins VR128:$src),
                    "movaps\t{$src, $dst|$dst, $src}", []>;
-let isLoad = 1, isReMaterializable = 1 in
+let isLoad = 1, isReMaterializable = 1, mayHaveSideEffects = 1 in
 def MOVAPSrm : PSI<0x28, MRMSrcMem, (outs VR128:$dst), (ins f128mem:$src),
                    "movaps\t{$src, $dst|$dst, $src}",
                    [(set VR128:$dst, (alignedloadv4f32 addr:$src))]>;
@@ -940,7 +940,7 @@ def STMXCSR : PSI<0xAE, MRM3m, (outs), (ins i32mem:$dst),
                   "stmxcsr\t$dst", [(int_x86_sse_stmxcsr addr:$dst)]>;
 
 // Alias instructions that map zero vector to pxor / xorp* for sse.
-let isReMaterializable = 1 in
+let isReMaterializable = 1, neverHasSideEffects = 1 in
 def V_SET0 : PSI<0x57, MRMInitReg, (outs VR128:$dst), (ins),
                  "xorps\t$dst, $dst",
                  [(set VR128:$dst, (v4i32 immAllZerosV))]>;
@@ -1003,7 +1003,7 @@ def MOVZSS2PSrm : SSI<0x10, MRMSrcMem, (outs VR128:$dst), (ins f32mem:$src),
 // Move Instructions
 def MOVSDrr : SDI<0x10, MRMSrcReg, (outs FR64:$dst), (ins FR64:$src),
                   "movsd\t{$src, $dst|$dst, $src}", []>;
-let isLoad = 1, isReMaterializable = 1 in
+let isLoad = 1, isReMaterializable = 1, mayHaveSideEffects = 1 in
 def MOVSDrm : SDI<0x10, MRMSrcMem, (outs FR64:$dst), (ins f64mem:$src),
                   "movsd\t{$src, $dst|$dst, $src}",
                   [(set FR64:$dst, (loadf64 addr:$src))]>;
@@ -1141,7 +1141,7 @@ def Int_COMISDrm: PDI<0x2F, MRMSrcMem, (outs), (ins VR128:$src1, f128mem:$src2),
 // start with 'Fs'.
 
 // Alias instructions that map fld0 to pxor for sse.
-let isReMaterializable = 1 in
+let isReMaterializable = 1, neverHasSideEffects = 1 in
 def FsFLD0SD : I<0xEF, MRMInitReg, (outs FR64:$dst), (ins),
                  "pxor\t$dst, $dst", [(set FR64:$dst, fpimm0)]>,
                Requires<[HasSSE2]>, TB, OpSize;
@@ -1330,7 +1330,7 @@ defm MIN : sse2_fp_binop_rm<0x5D, "min", X86fmin,
 // Move Instructions
 def MOVAPDrr : PDI<0x28, MRMSrcReg, (outs VR128:$dst), (ins VR128:$src),
                    "movapd\t{$src, $dst|$dst, $src}", []>;
-let isLoad = 1, isReMaterializable = 1 in
+let isLoad = 1, isReMaterializable = 1, mayHaveSideEffects = 1 in
 def MOVAPDrm : PDI<0x28, MRMSrcMem, (outs VR128:$dst), (ins f128mem:$src),
                    "movapd\t{$src, $dst|$dst, $src}",
                    [(set VR128:$dst, (alignedloadv2f64 addr:$src))]>;
@@ -2119,7 +2119,7 @@ def MFENCE : I<0xAE, MRM6m, (outs), (ins),
 
 
 // Alias instructions that map zero vector to pxor / xorp* for sse.
-let isReMaterializable = 1 in
+let isReMaterializable = 1, neverHasSideEffects = 1 in
   def V_SETALLONES : PDI<0x76, MRMInitReg, (outs VR128:$dst), (ins),
                          "pcmpeqd\t$dst, $dst",
                          [(set VR128:$dst, (v4i32 immAllOnesV))]>;
diff --git a/lib/Target/X86/X86InstrX86-64.td b/lib/Target/X86/X86InstrX86-64.td
index 91df425242c..ecdbf9eb817 100644
--- a/lib/Target/X86/X86InstrX86-64.td
+++ b/lib/Target/X86/X86InstrX86-64.td
@@ -201,7 +201,7 @@ def REP_STOSQ : RI<0xAB, RawFrm, (outs), (ins), "{rep;stosq|rep stosq}",
 def MOV64rr : RI<0x89, MRMDestReg, (outs GR64:$dst), (ins GR64:$src),
                  "mov{q}\t{$src, $dst|$dst, $src}", []>;
 
-let isReMaterializable = 1 in {
+let isReMaterializable = 1, neverHasSideEffects = 1 in {
 def MOV64ri : RIi64<0xB8, AddRegFrm, (outs GR64:$dst), (ins i64imm:$src),
                     "movabs{q}\t{$src, $dst|$dst, $src}",
                     [(set GR64:$dst, imm:$src)]>;
@@ -1105,13 +1105,14 @@ def PsMOVZX64rm32: I<0x8B, MRMSrcMem, (outs GR64:$dst), (ins i32mem:$src),
 // FIXME: remove when we can teach regalloc that xor reg, reg is ok.
 // FIXME: AddedComplexity gives MOV64r0 a higher priority than MOV64ri32. Remove
 // when we have a better way to specify isel priority.
-let Defs = [EFLAGS], AddedComplexity = 1, isReMaterializable = 1 in
+let Defs = [EFLAGS], AddedComplexity = 1, isReMaterializable = 1,
+    neverHasSideEffects = 1 in
 def MOV64r0  : RI<0x31, MRMInitReg,  (outs GR64:$dst), (ins),
                  "xor{l}\t${dst:subreg32}, ${dst:subreg32}",
                  [(set GR64:$dst, 0)]>;
 
 // Materialize i64 constant where top 32-bits are zero.
-let AddedComplexity = 1, isReMaterializable = 1 in
+let AddedComplexity = 1, isReMaterializable = 1, neverHasSideEffects = 1 in
 def MOV64ri64i32 : Ii32<0xB8, AddRegFrm, (outs GR64:$dst), (ins i64i32imm:$src),
                         "mov{l}\t{$src, ${dst:subreg32}|${dst:subreg32}, $src}",
                         [(set GR64:$dst, i64immZExt32:$src)]>;