[AArch64][Falkor] Avoid generating STRQro* instructions

[gberry]

Summary

STRQro* instructions are slower than the alternative ADD/STRQui expanded
instructions on Falkor, so avoid generating them unless we're optimizing
for code size.

[asb]

One of the usual AArch64 suspects should confirm, but this looks good to me.

One minor nit: might the comment "Avoid generating STRQro is if it is slow unless we're optimizing for code size" better be placed by the definition of UseSTQro rather than the predicated patterns?

[t.p.northover]

There should be a test, but other than that only one nit (also with the comment).

lib/Target/AArch64/AArch64InstrInfo.td

2136

Grammar looks sketchy; drop the first "is"?

[gberry]

Move/fix comment and add test case to address review comments

lib/Target/AArch64/AArch64.td

def FeaturePostRAScheduler : SubtargetFeature<"use-postra-scheduler",
     "UsePostRAScheduler", "true", "Schedule again after register allocation">;
 
 def FeatureSlowMisaligned128Store : SubtargetFeature<"slow-misaligned-128store",
     "Misaligned128StoreIsSlow", "true", "Misaligned 128 bit stores are slow">;
 
 def FeatureSlowPaired128 : SubtargetFeature<"slow-paired-128",
     "Paired128IsSlow", "true", "Paired 128 bit loads and stores are slow">;
 
+def FeatureSlowSTRQro : SubtargetFeature<"slow-strqro-store", "STRQroIsSlow",
+    "true", "STR of Q register with register offset is slow">;
+
 def FeatureAlternateSExtLoadCVTF32Pattern : SubtargetFeature<
     "alternate-sextload-cvt-f32-pattern", "UseAlternateSExtLoadCVTF32Pattern",
     "true", "Use alternative pattern for sextload convert to f32">;
 
 def FeatureArithmeticBccFusion : SubtargetFeature<
     "arith-bcc-fusion", "HasArithmeticBccFusion", "true",
     "CPU fuses arithmetic+bcc operations">;
 
def ProcFalkor  : SubtargetFeature<"falkor", "ARMProcFamily", "Falkor",
                                    FeatureCustomCheapAsMoveHandling,
                                    FeatureFPARMv8,
                                    FeatureNEON,
                                    FeaturePerfMon,
                                    FeaturePostRAScheduler,
                                    FeaturePredictableSelectIsExpensive,
                                    FeatureRDM,
                                    FeatureZCZeroing,
-                                   FeatureLSLFast
+                                   FeatureLSLFast,
+                                   FeatureSlowSTRQro
                                    ]>;
 
 def ProcThunderX2T99  : SubtargetFeature<"thunderx2t99", "ARMProcFamily",
                                          "ThunderX2T99",
                                          "Cavium ThunderX2 processors", [
                                           FeatureCRC,
                                           FeatureCrypto,
                                           FeatureFPARMv8,

lib/Target/AArch64/AArch64InstrFormats.td

def roX : LoadStore128RO<sz, V, opc, regtype, asm, (outs regtype:$Rt),
     let Inst{13} = 0b1;
   }
 
   def : ROInstAlias<asm, regtype, !cast<Instruction>(NAME # "roX")>;
 }
 
 multiclass Store128RO<bits<2> sz, bit V, bits<2> opc, RegisterClass regtype,
                       string asm, ValueType Ty, SDPatternOperator storeop> {
-  let AddedComplexity = 10, mayLoad = 0, mayStore = 1, hasSideEffects = 0 in
+  let mayLoad = 0, mayStore = 1, hasSideEffects = 0 in
   def roW : LoadStore128RO<sz, V, opc, regtype, asm, (outs),
                (ins regtype:$Rt, GPR64sp:$Rn, GPR32:$Rm, ro_Wextend128:$extend),
-                [(storeop (Ty regtype:$Rt),
-                          (ro_Windexed128 GPR64sp:$Rn, GPR32:$Rm,
-                                          ro_Wextend128:$extend))]>,
+                []>,
             Sched<[WriteSTIdx, ReadAdrBase]> {
     let Inst{13} = 0b0;
   }
 
-  let AddedComplexity = 10, mayLoad = 0, mayStore = 1, hasSideEffects = 0 in
+  let mayLoad = 0, mayStore = 1, hasSideEffects = 0 in
   def roX : LoadStore128RO<sz, V, opc, regtype, asm, (outs),
                (ins regtype:$Rt, GPR64sp:$Rn, GPR64:$Rm, ro_Xextend128:$extend),
-                [(storeop (Ty regtype:$Rt),
-                          (ro_Xindexed128 GPR64sp:$Rn, GPR64:$Rm,
-                                          ro_Xextend128:$extend))]>,
+                []>,
             Sched<[WriteSTIdx, ReadAdrBase]> {
     let Inst{13} = 0b1;
   }
 
   def : ROInstAlias<asm, regtype, !cast<Instruction>(NAME # "roX")>;
 }
 
 let mayLoad = 0, mayStore = 0, hasSideEffects = 1 in

lib/Target/AArch64/AArch64InstrInfo.td

 
 // AArch64 Instruction Predicate Definitions.
 // We could compute these on a per-module basis but doing so requires accessing
 // the Function object through the <Target>Subtarget and objections were raised
 // to that (see post-commit review comments for r301750).
 let RecomputePerFunction = 1 in {
   def ForCodeSize   : Predicate<"MF->getFunction()->optForSize()">;
   def NotForCodeSize   : Predicate<"!MF->getFunction()->optForSize()">;
+  def UseSTRQro : Predicate<"!Subtarget->isSTRQroSlow() || MF->getFunction()->optForSize()">;
 }
 
 include "AArch64InstrFormats.td"
 
 //===----------------------------------------------------------------------===//
 
 //===----------------------------------------------------------------------===//
 // Miscellaneous instructions.

 
 // Floating-point
 defm STRB : Store8RO< 0b00,  1, 0b00, FPR8,   "str", untyped, store>;
 defm STRH : Store16RO<0b01,  1, 0b00, FPR16,  "str", f16,     store>;
 defm STRS : Store32RO<0b10,  1, 0b00, FPR32,  "str", f32,     store>;
 defm STRD : Store64RO<0b11,  1, 0b00, FPR64,  "str", f64,     store>;
 defm STRQ : Store128RO<0b00, 1, 0b10, FPR128, "str", f128,    store>;
 
+// Avoid generating STRQro is if it is slow unless we're optimizing for code size.
+let Predicates = [UseSTRQro], AddedComplexity = 10 in {
+  def : Pat<(store (f128 FPR128:$Rt),
+                        (ro_Windexed128 GPR64sp:$Rn, GPR32:$Rm,
+                                        ro_Wextend128:$extend)),
+            (STRQroW FPR128:$Rt, GPR64sp:$Rn, GPR32:$Rm, ro_Wextend128:$extend)>;
+  def : Pat<(store (f128 FPR128:$Rt),
+                        (ro_Xindexed128 GPR64sp:$Rn, GPR64:$Rm,
+                                        ro_Xextend128:$extend)),
+            (STRQroX FPR128:$Rt, GPR64sp:$Rn, GPR64:$Rm, ro_Wextend128:$extend)>;
+}
+
 multiclass TruncStoreFrom64ROPat<ROAddrMode ro, SDPatternOperator storeop,
                                  Instruction STRW, Instruction STRX> {
 
   def : Pat<(storeop GPR64:$Rt,
                      (ro.Wpat GPR64sp:$Rn, GPR32:$Rm, ro.Wext:$extend)),
             (STRW (EXTRACT_SUBREG GPR64:$Rt, sub_32),
                   GPR64sp:$Rn, GPR32:$Rm, ro.Wext:$extend)>;
 
let Predicates = [IsLE] in {
   defm : VecROStorePat<ro64, v8i8, FPR64, STRDroW, STRDroX>;
   defm : VecROStorePat<ro64, v4f16, FPR64, STRDroW, STRDroX>;
 }
 
 defm : VecROStorePat<ro64, v1i64, FPR64, STRDroW, STRDroX>;
 defm : VecROStorePat<ro64, v1f64, FPR64, STRDroW, STRDroX>;
 
 // Match all store 128 bits width whose type is compatible with FPR128
-let Predicates = [IsLE] in {
+let Predicates = [IsLE, UseSTRQro] in {
   // We must use ST1 to store vectors in big-endian.
   defm : VecROStorePat<ro128, v2i64, FPR128, STRQroW, STRQroX>;
   defm : VecROStorePat<ro128, v2f64, FPR128, STRQroW, STRQroX>;
   defm : VecROStorePat<ro128, v4i32, FPR128, STRQroW, STRQroX>;
   defm : VecROStorePat<ro128, v4f32, FPR128, STRQroW, STRQroX>;
   defm : VecROStorePat<ro128, v8i16, FPR128, STRQroW, STRQroX>;
   defm : VecROStorePat<ro128, v16i8, FPR128, STRQroW, STRQroX>;
   defm : VecROStorePat<ro128, v8f16, FPR128, STRQroW, STRQroX>;

lib/Target/AArch64/AArch64Subtarget.h

protected:
 
   bool UseAA = false;
   bool PredictableSelectIsExpensive = false;
   bool BalanceFPOps = false;
   bool CustomAsCheapAsMove = false;
   bool UsePostRAScheduler = false;
   bool Misaligned128StoreIsSlow = false;
   bool Paired128IsSlow = false;
+  bool STRQroIsSlow = false;
   bool UseAlternateSExtLoadCVTF32Pattern = false;
   bool HasArithmeticBccFusion = false;
   bool HasArithmeticCbzFusion = false;
   bool HasFuseAES = false;
   bool HasFuseLiterals = false;
   bool DisableLatencySchedHeuristic = false;
   bool UseRSqrt = false;
   uint8_t MaxInterleaveFactor = 2;
public:
   bool hasRDM() const { return HasRDM; }
   bool balanceFPOps() const { return BalanceFPOps; }
   bool predictableSelectIsExpensive() const {
     return PredictableSelectIsExpensive;
   }
   bool hasCustomCheapAsMoveHandling() const { return CustomAsCheapAsMove; }
   bool isMisaligned128StoreSlow() const { return Misaligned128StoreIsSlow; }
   bool isPaired128Slow() const { return Paired128IsSlow; }
+  bool isSTRQroSlow() const { return STRQroIsSlow; }
   bool useAlternateSExtLoadCVTF32Pattern() const {
     return UseAlternateSExtLoadCVTF32Pattern;
   }
   bool hasArithmeticBccFusion() const { return HasArithmeticBccFusion; }
   bool hasArithmeticCbzFusion() const { return HasArithmeticCbzFusion; }
   bool hasFuseAES() const { return HasFuseAES; }
   bool hasFuseLiterals() const { return HasFuseLiterals; }