[ARM] Add a register class for GPR pairs without SP and use it. NFCI

[miyuki]

Summary

Currently Thumb2InstrInfo.cpp uses a register class which is
auto-generated by tablegen. Such approach is fragile because
auto-generated classes might change when other register classes are
added. For example, before https://reviews.llvm.org/D62667
we were using GPRPair_with_gsub_1_in_rGPRRegClass, but had to
change it to GPRPair_with_gsub_1_in_GPRwithAPSRnospRegClass
because the former class stopped being generated (this did not change
the functionality though).

This patch adds a register class consisting of even-odd GPR register
pairs from (R0, R1) to (R10, R11), which excludes (R12, SP) and uses
it in Thumb2InstrInfo.cpp instead of
GPRPair_with_gsub_1_in_GPRwithAPSRnospRegClass.

[miyuki]

llvm/test/CodeGen/ARM/ipra-reg-usage.ll

9

Note: the change in this line (git show --word-diff) is the order of some registers ...[-$r12_sp-] $r0_r1 $r2_r3 {+$r12_sp+}...

llvm/lib/Target/ARM/ARMRegisterInfo.td

let AltOrders = [(add (rotl QPR, 8),  (rotl DPair, 16)),
                    (add (trunc QPR, 8), (trunc DPair, 16))];
   let AltOrderSelect = [{
     return 1 + MF.getSubtarget<ARMSubtarget>().hasMVEIntegerOps();
   }];
 }
 
 // Pseudo-registers representing even-odd pairs of GPRs from R1 to R13/SP.
 // These are needed by instructions (e.g. ldrexd/strexd) requiring even-odd GPRs.
-def Tuples2R : RegisterTuples<[gsub_0, gsub_1],
-                              [(add R0, R2, R4, R6, R8, R10, R12),
-                               (add R1, R3, R5, R7, R9, R11, SP)]>;
+def Tuples2Rnosp : RegisterTuples<[gsub_0, gsub_1],
+                                  [(add R0, R2, R4, R6, R8, R10),
+                                   (add R1, R3, R5, R7, R9, R11)]>;
+
+def Tuples2Rsp   : RegisterTuples<[gsub_0, gsub_1],
+                                  [(add R12), (add SP)]>;
 
 // Register class representing a pair of even-odd GPRs.
-def GPRPair : RegisterClass<"ARM", [untyped], 64, (add Tuples2R)> {
+def GPRPair : RegisterClass<"ARM", [untyped], 64, (add Tuples2Rnosp, Tuples2Rsp)> {
+  let Size = 64; // 2 x 32 bits, we have no predefined type of that size.
+}
+
+// Register class representing a pair of even-odd GPRs, except (R12, SP).
+def GPRPairnosp : RegisterClass<"ARM", [untyped], 64, (add Tuples2Rnosp)> {
   let Size = 64; // 2 x 32 bits, we have no predefined type of that size.
 }
 
 // Pseudo-registers representing 3 consecutive D registers.
 def Tuples3D : RegisterTuples<[dsub_0, dsub_1, dsub_2],
                               [(shl DPR, 0),
                                (shl DPR, 1),
                                (shl DPR, 2)]>;

llvm/lib/Target/ARM/Thumb2InstrInfo.cpp

storeRegToStackSlot(MachineBasicBlock &MBB, MachineBasicBlock::iterator I,
   }
 
   if (ARM::GPRPairRegClass.hasSubClassEq(RC)) {
     // Thumb2 STRD expects its dest-registers to be in rGPR. Not a problem for
     // gsub_0, but needs an extra constraint for gsub_1 (which could be sp
     // otherwise).
     if (Register::isVirtualRegister(SrcReg)) {
       MachineRegisterInfo *MRI = &MF.getRegInfo();
-      MRI->constrainRegClass(SrcReg, &ARM::GPRPair_with_gsub_1_in_GPRwithAPSRnospRegClass);
+      MRI->constrainRegClass(SrcReg, &ARM::GPRPairnospRegClass);
     }
 
     MachineInstrBuilder MIB = BuildMI(MBB, I, DL, get(ARM::t2STRDi8));
     AddDReg(MIB, SrcReg, ARM::gsub_0, getKillRegState(isKill), TRI);
     AddDReg(MIB, SrcReg, ARM::gsub_1, 0, TRI);
     MIB.addFrameIndex(FI).addImm(0).addMemOperand(MMO).add(predOps(ARMCC::AL));
     return;
   }
loadRegFromStackSlot(MachineBasicBlock &MBB, MachineBasicBlock::iterator I,
   }
 
   if (ARM::GPRPairRegClass.hasSubClassEq(RC)) {
     // Thumb2 LDRD expects its dest-registers to be in rGPR. Not a problem for
     // gsub_0, but needs an extra constraint for gsub_1 (which could be sp
     // otherwise).
     if (Register::isVirtualRegister(DestReg)) {
       MachineRegisterInfo *MRI = &MF.getRegInfo();
-      MRI->constrainRegClass(DestReg,
-                             &ARM::GPRPair_with_gsub_1_in_GPRwithAPSRnospRegClass);
+      MRI->constrainRegClass(DestReg, &ARM::GPRPairnospRegClass);
     }
 
     MachineInstrBuilder MIB = BuildMI(MBB, I, DL, get(ARM::t2LDRDi8));
     AddDReg(MIB, DestReg, ARM::gsub_0, RegState::DefineNoRead, TRI);
     AddDReg(MIB, DestReg, ARM::gsub_1, RegState::DefineNoRead, TRI);
     MIB.addFrameIndex(FI).addImm(0).addMemOperand(MMO).add(predOps(ARMCC::AL));
 
     if (Register::isPhysicalRegister(DestReg))

llvm/test/CodeGen/ARM/ipra-reg-usage.ll

 ; RUN: llc -mcpu=cortex-a8 -enable-ipra -print-regusage -o /dev/null 2>&1 < %s | FileCheck %s
 ; ipra used to wrongly assumed that registers without subregisters were saved.
 ; In that example, r0 wouldn't be in the list of clobbered registers.
 target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64"
 target triple = "armv7-eabi"
 
 declare void @bar1()
 define void @foo()#0 {
-; CHECK: foo Clobbered Registers: $apsr $apsr_nzcv $cpsr $fpcxtns $fpcxts $fpexc $fpinst $fpscr $fpscr_nzcv $fpscr_nzcvqc $fpsid $itstate $pc $sp $spsr $vpr $zr $d0 $d1 $d2 $d3 $d4 $d5 $d6 $d7 $d16 $d17 $d18 $d19 $d20 $d21 $d22 $d23 $d24 $d25 $d26 $d27 $d28 $d29 $d30 $d31 $fpinst2 $mvfr0 $mvfr1 $mvfr2 $p0 $q0 $q1 $q2 $q3 $q8 $q9 $q10 $q11 $q12 $q13 $q14 $q15 $r0 $r1 $r2 $r3 $r12 $s0 $s1 $s2 $s3 $s4 $s5 $s6 $s7 $s8 $s9 $s10 $s11 $s12 $s13 $s14 $s15 $d0_d2 $d1_d3 $d2_d4 $d3_d5 $d4_d6 $d5_d7 $d6_d8 $d7_d9 $d14_d16 $d15_d17 $d16_d18 $d17_d19 $d18_d20 $d19_d21 $d20_d22 $d21_d23 $d22_d24 $d23_d25 $d24_d26 $d25_d27 $d26_d28 $d27_d29 $d28_d30 $d29_d31 $q0_q1 $q1_q2 $q2_q3 $q3_q4 $q7_q8 $q8_q9 $q9_q10 $q10_q11 $q11_q12 $q12_q13 $q13_q14 $q14_q15 $q0_q1_q2_q3 $q1_q2_q3_q4 $q2_q3_q4_q5 $q3_q4_q5_q6 $q5_q6_q7_q8 $q6_q7_q8_q9 $q7_q8_q9_q10 $q8_q9_q10_q11 $q9_q10_q11_q12 $q10_q11_q12_q13 $q11_q12_q13_q14 $q12_q13_q14_q15 $r12_sp $r0_r1 $r2_r3 $d0_d1_d2 $d1_d2_d3 $d2_d3_d4 $d3_d4_d5 $d4_d5_d6 $d5_d6_d7 $d6_d7_d8 $d7_d8_d9 $d14_d15_d16 $d15_d16_d17 $d16_d17_d18 $d17_d18_d19 $d18_d19_d20 $d19_d20_d21 $d20_d21_d22 $d21_d22_d23 $d22_d23_d24 $d23_d24_d25 $d24_d25_d26 $d25_d26_d27 $d26_d27_d28 $d27_d28_d29 $d28_d29_d30 $d29_d30_d31 $d0_d2_d4 $d1_d3_d5 $d2_d4_d6 $d3_d5_d7 $d4_d6_d8 $d5_d7_d9 $d6_d8_d10 $d7_d9_d11 $d12_d14_d16 $d13_d15_d17 $d14_d16_d18 $d15_d17_d19 $d16_d18_d20 $d17_d19_d21 $d18_d20_d22 $d19_d21_d23 $d20_d22_d24 $d21_d23_d25 $d22_d24_d26 $d23_d25_d27 $d24_d26_d28 $d25_d27_d29 $d26_d28_d30 $d27_d29_d31 $d0_d2_d4_d6 $d1_d3_d5_d7 $d2_d4_d6_d8 $d3_d5_d7_d9 $d4_d6_d8_d10 $d5_d7_d9_d11 $d6_d8_d10_d12 $d7_d9_d11_d13 $d10_d12_d14_d16 $d11_d13_d15_d17 $d12_d14_d16_d18 $d13_d15_d17_d19 $d14_d16_d18_d20 $d15_d17_d19_d21 $d16_d18_d20_d22 $d17_d19_d21_d23 $d18_d20_d22_d24 $d19_d21_d23_d25 $d20_d22_d24_d26 $d21_d23_d25_d27 $d22_d24_d26_d28 $d23_d25_d27_d29 $d24_d26_d28_d30 $d25_d27_d29_d31 $d1_d2 $d3_d4 $d5_d6 $d7_d8 $d15_d16 $d17_d18 $d19_d20 $d21_d22 $d23_d24 $d25_d26 $d27_d28 $d29_d30 $d1_d2_d3_d4 $d3_d4_d5_d6 $d5_d6_d7_d8 $d7_d8_d9_d10 $d13_d14_d15_d16 $d15_d16_d17_d18 $d17_d18_d19_d20 $d19_d20_d21_d22 $d21_d22_d23_d24 $d23_d24_d25_d26 $d25_d26_d27_d28 $d27_d28_d29_d30
+; CHECK: foo Clobbered Registers: $apsr $apsr_nzcv $cpsr $fpcxtns $fpcxts $fpexc $fpinst $fpscr $fpscr_nzcv $fpscr_nzcvqc $fpsid $itstate $pc $sp $spsr $vpr $zr $d0 $d1 $d2 $d3 $d4 $d5 $d6 $d7 $d16 $d17 $d18 $d19 $d20 $d21 $d22 $d23 $d24 $d25 $d26 $d27 $d28 $d29 $d30 $d31 $fpinst2 $mvfr0 $mvfr1 $mvfr2 $p0 $q0 $q1 $q2 $q3 $q8 $q9 $q10 $q11 $q12 $q13 $q14 $q15 $r0 $r1 $r2 $r3 $r12 $s0 $s1 $s2 $s3 $s4 $s5 $s6 $s7 $s8 $s9 $s10 $s11 $s12 $s13 $s14 $s15 $d0_d2 $d1_d3 $d2_d4 $d3_d5 $d4_d6 $d5_d7 $d6_d8 $d7_d9 $d14_d16 $d15_d17 $d16_d18 $d17_d19 $d18_d20 $d19_d21 $d20_d22 $d21_d23 $d22_d24 $d23_d25 $d24_d26 $d25_d27 $d26_d28 $d27_d29 $d28_d30 $d29_d31 $q0_q1 $q1_q2 $q2_q3 $q3_q4 $q7_q8 $q8_q9 $q9_q10 $q10_q11 $q11_q12 $q12_q13 $q13_q14 $q14_q15 $q0_q1_q2_q3 $q1_q2_q3_q4 $q2_q3_q4_q5 $q3_q4_q5_q6 $q5_q6_q7_q8 $q6_q7_q8_q9 $q7_q8_q9_q10 $q8_q9_q10_q11 $q9_q10_q11_q12 $q10_q11_q12_q13 $q11_q12_q13_q14 $q12_q13_q14_q15 $r0_r1 $r2_r3 $r12_sp $d0_d1_d2 $d1_d2_d3 $d2_d3_d4 $d3_d4_d5 $d4_d5_d6 $d5_d6_d7 $d6_d7_d8 $d7_d8_d9 $d14_d15_d16 $d15_d16_d17 $d16_d17_d18 $d17_d18_d19 $d18_d19_d20 $d19_d20_d21 $d20_d21_d22 $d21_d22_d23 $d22_d23_d24 $d23_d24_d25 $d24_d25_d26 $d25_d26_d27 $d26_d27_d28 $d27_d28_d29 $d28_d29_d30 $d29_d30_d31 $d0_d2_d4 $d1_d3_d5 $d2_d4_d6 $d3_d5_d7 $d4_d6_d8 $d5_d7_d9 $d6_d8_d10 $d7_d9_d11 $d12_d14_d16 $d13_d15_d17 $d14_d16_d18 $d15_d17_d19 $d16_d18_d20 $d17_d19_d21 $d18_d20_d22 $d19_d21_d23 $d20_d22_d24 $d21_d23_d25 $d22_d24_d26 $d23_d25_d27 $d24_d26_d28 $d25_d27_d29 $d26_d28_d30 $d27_d29_d31 $d0_d2_d4_d6 $d1_d3_d5_d7 $d2_d4_d6_d8 $d3_d5_d7_d9 $d4_d6_d8_d10 $d5_d7_d9_d11 $d6_d8_d10_d12 $d7_d9_d11_d13 $d10_d12_d14_d16 $d11_d13_d15_d17 $d12_d14_d16_d18 $d13_d15_d17_d19 $d14_d16_d18_d20 $d15_d17_d19_d21 $d16_d18_d20_d22 $d17_d19_d21_d23 $d18_d20_d22_d24 $d19_d21_d23_d25 $d20_d22_d24_d26 $d21_d23_d25_d27 $d22_d24_d26_d28 $d23_d25_d27_d29 $d24_d26_d28_d30 $d25_d27_d29_d31 $d1_d2 $d3_d4 $d5_d6 $d7_d8 $d15_d16 $d17_d18 $d19_d20 $d21_d22 $d23_d24 $d25_d26 $d27_d28 $d29_d30 $d1_d2_d3_d4 $d3_d4_d5_d6 $d5_d6_d7_d8 $d7_d8_d9_d10 $d13_d14_d15_d16 $d15_d16_d17_d18 $d17_d18_d19_d20 $d19_d20_d21_d22 $d21_d22_d23_d24 $d23_d24_d25_d26 $d25_d26_d27_d28 $d27_d28_d29_d30
   call void @bar1()
   call void @bar2()
   ret void
 }
 
 @llvm.used = appending global [1 x i8*] [i8* bitcast (void ()* @foo to i8*)]
 
 declare void @bar2()
 attributes #0 = {nounwind}