[ARM] Some saturation instructions not DSP-only

[bogden]

Summary

Commit 276701 requires that targets have the DSP extensions to use
certain saturating instructions. This requires some corrections.

For ARM ISA the instructions in question are available in all v6*
architectures.

For Thumb2, the instructions in question are available from v6T2.
SSAT and USAT are part of the base architecture while SSAT16 and
USAT16 require the DSP extensions.

[rengolin]

Hi Bernie,

This is much clearer, thanks!

--renato

[rengolin]

Backported this to release 3.9 (together with the original patch).

Thanks!

lib/Target/ARM/ARMISelLowering.cpp

 SDValue ARMTargetLowering::LowerSELECT_CC(SDValue Op, SelectionDAG &DAG) const {
 
   EVT VT = Op.getValueType();
   SDLoc dl(Op);
 
   // Try to convert two saturating conditional selects into a single SSAT
   SDValue SatValue;
   uint64_t SatConstant;
-  if (Subtarget->hasDSP() &&
+  if (((!Subtarget->isThumb() && Subtarget->hasV6Ops()) || Subtarget->isThumb2()) &&
       isSaturatingConditional(Op, SatValue, SatConstant))
     return DAG.getNode(ARMISD::SSAT, dl, VT, SatValue,
                        DAG.getConstant(countTrailingOnes(SatConstant), dl, VT));
 
   SDValue LHS = Op.getOperand(0);
   SDValue RHS = Op.getOperand(1);
   ISD::CondCode CC = cast<CondCodeSDNode>(Op.getOperand(4))->get();
   SDValue TrueVal = Op.getOperand(2);

lib/Target/ARM/ARMInstrInfo.td

def USADA8 : AI<(outs GPR:$Rd), (ins GPR:$Rn, GPR:$Rm, GPR:$Ra),
   let Inst{3-0} = Rn;
 }
 
 // Signed/Unsigned saturate
 
 def SSAT : AI<(outs GPRnopc:$Rd),
               (ins imm1_32:$sat_imm, GPRnopc:$Rn, shift_imm:$sh),
               SatFrm, NoItinerary, "ssat", "\t$Rd, $sat_imm, $Rn$sh", []>,
-              Requires<[HasDSP]>{
+              Requires<[IsARM,HasV6]>{
   bits<4> Rd;
   bits<5> sat_imm;
   bits<4> Rn;
   bits<8> sh;
   let Inst{27-21} = 0b0110101;
   let Inst{5-4} = 0b01;
   let Inst{20-16} = sat_imm;
   let Inst{15-12} = Rd;
   let Inst{11-7} = sh{4-0};
   let Inst{6} = sh{5};
   let Inst{3-0} = Rn;
 }
 
 def SSAT16 : AI<(outs GPRnopc:$Rd),
                 (ins imm1_16:$sat_imm, GPRnopc:$Rn), SatFrm,
                 NoItinerary, "ssat16", "\t$Rd, $sat_imm, $Rn", []>,
-                Requires<[HasDSP]>{
+                Requires<[IsARM,HasV6]>{
   bits<4> Rd;
   bits<4> sat_imm;
   bits<4> Rn;
   let Inst{27-20} = 0b01101010;
   let Inst{11-4} = 0b11110011;
   let Inst{15-12} = Rd;
   let Inst{19-16} = sat_imm;
   let Inst{3-0} = Rn;
 }
 
 def USAT : AI<(outs GPRnopc:$Rd),
               (ins imm0_31:$sat_imm, GPRnopc:$Rn, shift_imm:$sh),
               SatFrm, NoItinerary, "usat", "\t$Rd, $sat_imm, $Rn$sh", []>,
-              Requires<[HasDSP]>{
+              Requires<[IsARM,HasV6]> {
   bits<4> Rd;
   bits<5> sat_imm;
   bits<4> Rn;
   bits<8> sh;
   let Inst{27-21} = 0b0110111;
   let Inst{5-4} = 0b01;
   let Inst{15-12} = Rd;
   let Inst{11-7} = sh{4-0};
   let Inst{6} = sh{5};
   let Inst{20-16} = sat_imm;
   let Inst{3-0} = Rn;
 }
 
 def USAT16 : AI<(outs GPRnopc:$Rd),
                 (ins imm0_15:$sat_imm, GPRnopc:$Rn), SatFrm,
                 NoItinerary, "usat16", "\t$Rd, $sat_imm, $Rn", []>,
-                Requires<[HasDSP]>{
+                Requires<[IsARM,HasV6]>{
   bits<4> Rd;
   bits<4> sat_imm;
   bits<4> Rn;
   let Inst{27-20} = 0b01101110;
   let Inst{11-4} = 0b11110011;
   let Inst{15-12} = Rd;
   let Inst{19-16} = sat_imm;
   let Inst{3-0} = Rn;

lib/Target/ARM/ARMInstrThumb2.td

class T2SatI<dag oops, dag iops, InstrItinClass itin,
   let Inst{14-12} = sh{4-2};
   let Inst{7-6}   = sh{1-0};
 }
 
 def t2SSAT: T2SatI<
               (outs rGPR:$Rd),
               (ins imm1_32:$sat_imm, rGPR:$Rn, t2_shift_imm:$sh),
               NoItinerary, "ssat", "\t$Rd, $sat_imm, $Rn$sh", []>,
-              Requires<[IsThumb2, HasDSP]> {
+              Requires<[IsThumb2]> {
   let Inst{31-27} = 0b11110;
   let Inst{25-22} = 0b1100;
   let Inst{20} = 0;
   let Inst{15} = 0;
   let Inst{5}  = 0;
 }
 
 def t2SSAT16: T2SatI<
def t2SSAT16: T2SatI<
   let Inst{7-6} = 0b00;    // imm2 = '00'
   let Inst{5-4} = 0b00;
 }
 
 def t2USAT: T2SatI<
                (outs rGPR:$Rd),
                (ins imm0_31:$sat_imm, rGPR:$Rn, t2_shift_imm:$sh),
                 NoItinerary, "usat", "\t$Rd, $sat_imm, $Rn$sh", []>,
-                Requires<[IsThumb2, HasDSP]> {
+                Requires<[IsThumb2]> {
   let Inst{31-27} = 0b11110;
   let Inst{25-22} = 0b1110;
   let Inst{20} = 0;
   let Inst{15} = 0;
 }
 
 def t2USAT16: T2SatI<(outs rGPR:$Rd), (ins imm0_15:$sat_imm, rGPR:$Rn),
                      NoItinerary,