[X86] Remove isReMaterializable from X87 floating point constant loads and constant pool loads.

[craig.topper]

Summary

These instructions update FPSW so they aren't generically safe to rematerialize into any location if FPSW is live for a comparison result. They also use FPCW for exception masking control. Though the only exception they can generate is stack overflow and we manage the stack ourselves so that's not really going to occur.

[RKSimon]

LGTM

lib/Target/X86/X86InstrFPStack.td

 } // Predicates = [HasCMov]
 } // SchedRW
 
 // Floating point loads & stores.
 let SchedRW = [WriteLoad] in {
 let canFoldAsLoad = 1 in {
 def LD_Fp32m   : FpIf32<(outs RFP32:$dst), (ins f32mem:$src), ZeroArgFP,
                   [(set RFP32:$dst, (loadf32 addr:$src))]>;
-let isReMaterializable = 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,
                   [(set RFP80:$dst, (loadf80 addr:$src))]>;
 } // canFoldAsLoad
 def LD_Fp32m64 : FpIf64<(outs RFP64:$dst), (ins f32mem:$src), ZeroArgFP,
                   [(set RFP64:$dst, (f64 (extloadf32 addr:$src)))]>;
 def LD_Fp64m80 : FpI_<(outs RFP80:$dst), (ins f64mem:$src), ZeroArgFP,
                   [(set RFP80:$dst, (f80 (extloadf64 addr:$src)))]>;

 let SchedRW = [WriteMove] in {
 def LD_Frr   : FPI<0xD9, MRM0r, (outs), (ins RSTi:$op), "fld\t$op">;
 def ST_Frr   : FPI<0xDD, MRM2r, (outs), (ins RSTi:$op), "fst\t$op">;
 def ST_FPrr  : FPI<0xDD, MRM3r, (outs), (ins RSTi:$op), "fstp\t$op">;
 def XCH_F    : FPI<0xD9, MRM1r, (outs), (ins RSTi:$op), "fxch\t$op">;
 }
 
 // Floating point constant loads.
-let isReMaterializable = 1, SchedRW = [WriteZero] in {
+let SchedRW = [WriteZero] in {
 def LD_Fp032 : FpIf32<(outs RFP32:$dst), (ins), ZeroArgFP,
                 [(set RFP32:$dst, fpimm0)]>;
 def LD_Fp132 : FpIf32<(outs RFP32:$dst), (ins), ZeroArgFP,
                 [(set RFP32:$dst, fpimm1)]>;
 def LD_Fp064 : FpIf64<(outs RFP64:$dst), (ins), ZeroArgFP,
                 [(set RFP64:$dst, fpimm0)]>;
 def LD_Fp164 : FpIf64<(outs RFP64:$dst), (ins), ZeroArgFP,
                 [(set RFP64:$dst, fpimm1)]>;

lib/Target/X86/X86InstrInfo.cpp

bool X86InstrInfo::isReallyTriviallyReMaterializable(const MachineInstr &MI,
                                                      AliasAnalysis *AA) const {
   switch (MI.getOpcode()) {
   default: break;
   case X86::MOV8rm:
   case X86::MOV8rm_NOREX:
   case X86::MOV16rm:
   case X86::MOV32rm:
   case X86::MOV64rm:
-  case X86::LD_Fp64m:
   case X86::MOVSSrm:
   case X86::MOVSDrm:
   case X86::MOVAPSrm:
   case X86::MOVUPSrm:
   case X86::MOVAPDrm:
   case X86::MOVUPDrm:
   case X86::MOVDQArm:
   case X86::MOVDQUrm: