[ARM] Use isFMAFasterThanFMulAndFAdd for scalars as well as MVE vectors

[dmgreen]

Summary

This adds extra scalar handling to isFMAFasterThanFMulAndFAdd, allowing the target independent code to handle more folds in more situations (for example if the fast math flags are present, but the global AllowFPOpFusion option isnt). It also splits apart the HasSlowFPVMLx into HasSlowFPVFMx, to allow VFMA and VMLA to be controlled separately if needed.

[samparker]

llvm/lib/Target/ARM/ARMISelLowering.cpp

15024

Is there a way this logic can sit in Subtarget to avoid it being a tablegen predicate as well as code here? I'm hopeless with our FP architectures... does FullFP16 infer VFP4?

[dmgreen]

llvm/lib/Target/ARM/ARMISelLowering.cpp

15024

Yeah, that sounds good. I'll try and move it around.

FullFP16 implies fp-armv8 I'm pretty sure. So at least VFP4.

[dmgreen]

Move more of the logic into Subtarget.

[samparker]

LGTM

llvm/lib/Target/ARM/ARM.td

def FeatureNonpipelinedVFP : SubtargetFeature<"nonpipelined-vfp",
                                               "VFP instructions are not pipelined">;
 
 // Some processors have FP multiply-accumulate instructions that don't
 // play nicely with other VFP / NEON instructions, and it's generally better
 // to just not use them.
 def FeatureHasSlowFPVMLx  : SubtargetFeature<"slowfpvmlx", "SlowFPVMLx", "true",
                                              "Disable VFP / NEON MAC instructions">;
 
+// VFPv4 added VFMA instructions that can similar be fast or slow.
+def FeatureHasSlowFPVFMx  : SubtargetFeature<"slowfpvfmx", "SlowFPVFMx", "true",
+                                             "Disable VFP / NEON FMA instructions">;
+
 // Cortex-A8 / A9 Advanced SIMD has multiplier accumulator forwarding.
 def FeatureVMLxForwarding : SubtargetFeature<"vmlx-forwarding",
                                              "HasVMLxForwarding", "true",
                                              "Has multiplier accumulator forwarding">;
 
 // Disable 32-bit to 16-bit narrowing for experimentation.
 def FeaturePref32BitThumb : SubtargetFeature<"32bit", "Pref32BitThumb", "true",
                                              "Prefer 32-bit Thumb instrs">;
def ProcExynos  : SubtargetFeature<"exynos", "ARMProcFamily", "Exynos",
                                     FeatureSplatVFPToNeon,
                                     FeatureSlowVGETLNi32,
                                     FeatureSlowVDUP32,
                                     FeatureSlowFPBrcc,
                                     FeatureProfUnpredicate,
                                     FeatureHWDivThumb,
                                     FeatureHWDivARM,
                                     FeatureHasSlowFPVMLx,
+                                    FeatureHasSlowFPVFMx,
                                     FeatureHasRetAddrStack,
                                     FeatureFuseLiterals,
                                     FeatureFuseAES,
                                     FeatureExpandMLx,
                                     FeatureCrypto,
                                     FeatureCRC]>;
 
 def ProcR4      : SubtargetFeature<"r4", "ARMProcFamily", "CortexR4",
def : Processor<"arm1156t2f-s",     ARMV6Itineraries,   [ARMv6t2,
                                                          FeatureVFP2,
                                                          FeatureHasSlowFPVMLx]>;
 
 def : ProcessorModel<"cortex-a5",   CortexA8Model,      [ARMv7a, ProcA5,
                                                          FeatureHasRetAddrStack,
                                                          FeatureTrustZone,
                                                          FeatureSlowFPBrcc,
                                                          FeatureHasSlowFPVMLx,
+                                                         FeatureHasSlowFPVFMx,
                                                          FeatureVMLxForwarding,
                                                          FeatureMP,
                                                          FeatureVFP4]>;
 
 def : ProcessorModel<"cortex-a7",   CortexA8Model,      [ARMv7a, ProcA7,
                                                          FeatureHasRetAddrStack,
                                                          FeatureTrustZone,
                                                          FeatureSlowFPBrcc,
                                                          FeatureHasVMLxHazards,
                                                          FeatureHasSlowFPVMLx,
+                                                         FeatureHasSlowFPVFMx,
                                                          FeatureVMLxForwarding,
                                                          FeatureMP,
                                                          FeatureVFP4,
                                                          FeatureVirtualization]>;
 
 def : ProcessorModel<"cortex-a8",   CortexA8Model,      [ARMv7a, ProcA8,
                                                          FeatureHasRetAddrStack,
                                                          FeatureNonpipelinedVFP,
                                                          FeatureTrustZone,
                                                          FeatureSlowFPBrcc,
                                                          FeatureHasVMLxHazards,
                                                          FeatureHasSlowFPVMLx,
+                                                         FeatureHasSlowFPVFMx,
                                                          FeatureVMLxForwarding]>;
 
 def : ProcessorModel<"cortex-a9",   CortexA9Model,      [ARMv7a, ProcA9,
                                                          FeatureHasRetAddrStack,
                                                          FeatureTrustZone,
                                                          FeatureHasVMLxHazards,
                                                          FeatureVMLxForwarding,
                                                          FeatureFP16,
def : ProcessorModel<"swift",       SwiftModel,         [ARMv7a, ProcSwift,
                                                          FeatureVFP4,
                                                          FeatureUseWideStrideVFP,
                                                          FeatureMP,
                                                          FeatureHWDivThumb,
                                                          FeatureHWDivARM,
                                                          FeatureAvoidPartialCPSR,
                                                          FeatureAvoidMOVsShOp,
                                                          FeatureHasSlowFPVMLx,
+                                                         FeatureHasSlowFPVFMx,
                                                          FeatureHasVMLxHazards,
                                                          FeatureProfUnpredicate,
                                                          FeaturePrefISHSTBarrier,
                                                          FeatureSlowOddRegister,
                                                          FeatureSlowLoadDSubreg,
                                                          FeatureSlowVGETLNi32,
                                                          FeatureSlowVDUP32,
                                                          FeatureUseMISched,
                                                          FeatureNoPostRASched]>;
 
 def : ProcessorModel<"cortex-r4",   CortexA8Model,      [ARMv7r, ProcR4,
                                                          FeatureHasRetAddrStack,
                                                          FeatureAvoidPartialCPSR]>;
 
 def : ProcessorModel<"cortex-r4f",  CortexA8Model,      [ARMv7r, ProcR4,
                                                          FeatureHasRetAddrStack,
                                                          FeatureSlowFPBrcc,
                                                          FeatureHasSlowFPVMLx,
+                                                         FeatureHasSlowFPVFMx,
                                                          FeatureVFP3_D16,
                                                          FeatureAvoidPartialCPSR]>;
 
 def : ProcessorModel<"cortex-r5",   CortexA8Model,      [ARMv7r, ProcR5,
                                                          FeatureHasRetAddrStack,
                                                          FeatureVFP3_D16,
                                                          FeatureSlowFPBrcc,
                                                          FeatureHWDivARM,
                                                          FeatureHasSlowFPVMLx,
+                                                         FeatureHasSlowFPVFMx,
                                                          FeatureAvoidPartialCPSR]>;
 
 def : ProcessorModel<"cortex-r7",   CortexA8Model,      [ARMv7r, ProcR7,
                                                          FeatureHasRetAddrStack,
                                                          FeatureVFP3_D16,
                                                          FeatureFP16,
                                                          FeatureMP,
                                                          FeatureSlowFPBrcc,
                                                          FeatureHWDivARM,
                                                          FeatureHasSlowFPVMLx,
+                                                         FeatureHasSlowFPVFMx,
                                                          FeatureAvoidPartialCPSR]>;
 
 def : ProcessorModel<"cortex-r8",   CortexA8Model,      [ARMv7r,
                                                          FeatureHasRetAddrStack,
                                                          FeatureVFP3_D16,
                                                          FeatureFP16,
                                                          FeatureMP,
                                                          FeatureSlowFPBrcc,
                                                          FeatureHWDivARM,
                                                          FeatureHasSlowFPVMLx,
+                                                         FeatureHasSlowFPVFMx,
                                                          FeatureAvoidPartialCPSR]>;
 
 def : ProcessorModel<"cortex-m3",   CortexM4Model,      [ARMv7m,
                                                          ProcM3,
                                                          FeaturePrefLoopAlign32,
                                                          FeatureUseMISched,
                                                          FeatureHasNoBranchPredictor]>;
 
 def : ProcessorModel<"sc300",       CortexM4Model,      [ARMv7m,
                                                          ProcM3,
                                                          FeatureUseMISched,
                                                          FeatureHasNoBranchPredictor]>;
 
 def : ProcessorModel<"cortex-m4", CortexM4Model,        [ARMv7em,
                                                          FeatureVFP4_D16_SP,
                                                          FeaturePrefLoopAlign32,
                                                          FeatureHasSlowFPVMLx,
+                                                         FeatureHasSlowFPVFMx,
                                                          FeatureUseMISched,
                                                          FeatureHasNoBranchPredictor]>;
 
 def : ProcNoItin<"cortex-m7",                           [ARMv7em,
                                                          FeatureFPARMv8_D16]>;
 
 def : ProcNoItin<"cortex-m23",                          [ARMv8mBaseline,
                                                          FeatureNoMovt]>;
 
 def : ProcessorModel<"cortex-m33", CortexM4Model,       [ARMv8mMainline,
                                                          FeatureDSP,
                                                          FeatureFPARMv8_D16_SP,
                                                          FeaturePrefLoopAlign32,
                                                          FeatureHasSlowFPVMLx,
+                                                         FeatureHasSlowFPVFMx,
                                                          FeatureUseMISched,
                                                          FeatureHasNoBranchPredictor]>;
 
 def : ProcessorModel<"cortex-m35p", CortexM4Model,      [ARMv8mMainline,
                                                          FeatureDSP,
                                                          FeatureFPARMv8_D16_SP,
                                                          FeaturePrefLoopAlign32,
                                                          FeatureHasSlowFPVMLx,
+                                                         FeatureHasSlowFPVFMx,
                                                          FeatureUseMISched,
                                                          FeatureHasNoBranchPredictor]>;
 
 
 def : ProcNoItin<"cortex-a32",                           [ARMv8a,
                                                          FeatureHWDivThumb,
                                                          FeatureHWDivARM,
                                                          FeatureCrypto,
def : ProcessorModel<"cyclone",     SwiftModel,         [ARMv8a, ProcSwift,
                                                          FeatureNEONForFP,
                                                          FeatureVFP4,
                                                          FeatureMP,
                                                          FeatureHWDivThumb,
                                                          FeatureHWDivARM,
                                                          FeatureAvoidPartialCPSR,
                                                          FeatureAvoidMOVsShOp,
                                                          FeatureHasSlowFPVMLx,
+                                                         FeatureHasSlowFPVFMx,
                                                          FeatureCrypto,
                                                          FeatureUseMISched,
                                                          FeatureZCZeroing,
                                                          FeatureNoPostRASched]>;
 
 def : ProcNoItin<"exynos-m3",                           [ARMv8a, ProcExynos]>;
 def : ProcNoItin<"exynos-m4",                           [ARMv82a, ProcExynos,
                                                          FeatureFullFP16,

llvm/lib/Target/ARM/ARMISelLowering.cpp

 /// lower a pair of fmul and fadd to the latter so it's not clear that there
 /// would be a gain or that the gain would be worthwhile enough to risk
 /// correctness bugs.
 ///
 /// For MVE, we set this to true as it helps simplify the need for some
 /// patterns (and we don't have the non-fused floating point instruction).
 bool ARMTargetLowering::isFMAFasterThanFMulAndFAdd(const MachineFunction &MF,
                                                    EVT VT) const {
-  if (!Subtarget->hasMVEFloatOps())
-    return false;
-
   if (!VT.isSimple())
     return false;
 
   switch (VT.getSimpleVT().SimpleTy) {
   case MVT::v4f32:
   case MVT::v8f16:
-    return true;
+    return Subtarget->hasMVEFloatOps();
+  case MVT::f16:
+    return Subtarget->hasFullFP16() && !Subtarget->isTargetDarwin() &&
+           Subtarget->useFPVFMx();
+  case MVT::f32:
+    return Subtarget->hasVFP4Base() && !Subtarget->isTargetDarwin() &&
+           Subtarget->useFPVFMx();
+  case MVT::f64:
+    return Subtarget->hasVFP4Base() && Subtarget->hasFP64() &&
+           !Subtarget->isTargetDarwin() && Subtarget->useFPVFMx();
   default:
     break;
   }
 
   return false;
 }
 
 static bool isLegalT1AddressImmediate(int64_t V, EVT VT) {

llvm/lib/Target/ARM/ARMPredicates.td

 // Prefer fused MAC for fp mul + add over fp VMLA / VMLS if they are available.
 // But only select them if more precision in FP computation is allowed, and when
 // they are not slower than a mul + add sequence.
 // Do not use them for Darwin platforms.
 def UseFusedMAC      : Predicate<"(TM.Options.AllowFPOpFusion =="
                                  " FPOpFusion::Fast && "
                                  " Subtarget->hasVFP4Base()) && "
                                  "!Subtarget->isTargetDarwin() &&"
-                                 "Subtarget->useFPVMLx()">;
+                                 "Subtarget->useFPVFMx()">;
 
 def HasFastVGETLNi32 : Predicate<"!Subtarget->hasSlowVGETLNi32()">;
 def HasSlowVGETLNi32 : Predicate<"Subtarget->hasSlowVGETLNi32()">;
 
 def HasFastVDUP32 : Predicate<"!Subtarget->hasSlowVDUP32()">;
 def HasSlowVDUP32 : Predicate<"Subtarget->hasSlowVDUP32()">;
 
 def UseVMOVSR : Predicate<"Subtarget->preferVMOVSR() ||"

llvm/lib/Target/ARM/ARMSubtarget.h

protected:
   /// UseMulOps - True if non-microcoded fused integer multiply-add and
   /// multiply-subtract instructions should be used.
   bool UseMulOps = false;
 
   /// SlowFPVMLx - If the VFP2 / NEON instructions are available, indicates
   /// whether the FP VML[AS] instructions are slow (if so, don't use them).
   bool SlowFPVMLx = false;
 
+  /// SlowFPVFMx - If the VFP4 / NEON instructions are available, indicates
+  /// whether the FP VFM[AS] instructions are slow (if so, don't use them).
+  bool SlowFPVFMx = false;
+
   /// HasVMLxForwarding - If true, NEON has special multiplier accumulator
   /// forwarding to allow mul + mla being issued back to back.
   bool HasVMLxForwarding = false;
 
   /// SlowFPBrcc - True if floating point compare + branch is slow.
   bool SlowFPBrcc = false;
 
   /// InThumbMode - True if compiling for Thumb, false for ARM.
public:
   bool hasAcquireRelease() const { return HasAcquireRelease; }
 
   bool hasAnyDataBarrier() const {
     return HasDataBarrier || (hasV6Ops() && !isThumb());
   }
 
   bool useMulOps() const { return UseMulOps; }
   bool useFPVMLx() const { return !SlowFPVMLx; }
+  bool useFPVFMx() const { return !SlowFPVFMx; }
   bool hasVMLxForwarding() const { return HasVMLxForwarding; }
   bool isFPBrccSlow() const { return SlowFPBrcc; }
   bool hasFP64() const { return HasFP64; }
   bool hasPerfMon() const { return HasPerfMon; }
   bool hasTrustZone() const { return HasTrustZone; }
   bool has8MSecExt() const { return Has8MSecExt; }
   bool hasZeroCycleZeroing() const { return HasZeroCycleZeroing; }
   bool hasFPAO() const { return HasFPAO; }

llvm/lib/Target/ARM/ARMTargetTransformInfo.h

const FeatureBitset InlineFeatureWhitelist = {
       ARM::FeatureFPAO, ARM::FeatureFuseAES, ARM::FeatureZCZeroing,
       ARM::FeatureProfUnpredicate, ARM::FeatureSlowVGETLNi32,
       ARM::FeatureSlowVDUP32, ARM::FeaturePreferVMOVSR,
       ARM::FeaturePrefISHSTBarrier, ARM::FeatureMuxedUnits,
       ARM::FeatureSlowOddRegister, ARM::FeatureSlowLoadDSubreg,
       ARM::FeatureDontWidenVMOVS, ARM::FeatureExpandMLx,
       ARM::FeatureHasVMLxHazards, ARM::FeatureNEONForFPMovs,
       ARM::FeatureNEONForFP, ARM::FeatureCheckVLDnAlign,
-      ARM::FeatureHasSlowFPVMLx, ARM::FeatureVMLxForwarding,
-      ARM::FeaturePref32BitThumb, ARM::FeatureAvoidPartialCPSR,
-      ARM::FeatureCheapPredicableCPSR, ARM::FeatureAvoidMOVsShOp,
-      ARM::FeatureHasRetAddrStack, ARM::FeatureHasNoBranchPredictor,
-      ARM::FeatureDSP, ARM::FeatureMP, ARM::FeatureVirtualization,
-      ARM::FeatureMClass, ARM::FeatureRClass, ARM::FeatureAClass,
-      ARM::FeatureNaClTrap, ARM::FeatureStrictAlign, ARM::FeatureLongCalls,
-      ARM::FeatureExecuteOnly, ARM::FeatureReserveR9, ARM::FeatureNoMovt,
-      ARM::FeatureNoNegativeImmediates
+      ARM::FeatureHasSlowFPVMLx, ARM::FeatureHasSlowFPVFMx,
+      ARM::FeatureVMLxForwarding, ARM::FeaturePref32BitThumb,
+      ARM::FeatureAvoidPartialCPSR, ARM::FeatureCheapPredicableCPSR,
+      ARM::FeatureAvoidMOVsShOp, ARM::FeatureHasRetAddrStack,
+      ARM::FeatureHasNoBranchPredictor, ARM::FeatureDSP, ARM::FeatureMP,
+      ARM::FeatureVirtualization, ARM::FeatureMClass, ARM::FeatureRClass,
+      ARM::FeatureAClass, ARM::FeatureNaClTrap, ARM::FeatureStrictAlign,
+      ARM::FeatureLongCalls, ARM::FeatureExecuteOnly, ARM::FeatureReserveR9,
+      ARM::FeatureNoMovt, ARM::FeatureNoNegativeImmediates
   };
 
   const ARMSubtarget *getST() const { return ST; }
   const ARMTargetLowering *getTLI() const { return TLI; }
 
 public:
   explicit ARMTTIImpl(const ARMBaseTargetMachine *TM, const Function &F)
       : BaseT(TM, F.getParent()->getDataLayout()), ST(TM->getSubtargetImpl(F)),

llvm/test/CodeGen/ARM/cortex-a57-misched-vfma.ll

 ; > VMULS common latency = 5
 ; CHECK:       Latency            : 5
 ; CHECK:       Successors:
 ; CHECK:       Data
 ; > VMULS read-advanced latency to VMLSS = 0
 ; CHECK-SAME:  Latency=0
 
 ; CHECK-DEFAULT: VMLSS
-; CHECK-FAST:    VFMSS
-; > VMLSS common latency = 9
+; CHECK-FAST:    VFNMSS
+; > VFNMSS common latency = 9
 ; CHECK:       Latency            : 9
 ; CHECK:       Successors:
 ; CHECK:       Data
-; > VMLSS read-advanced latency to the next VMLSS = 4
+; > VFNMSS read-advanced latency to the next VMLSS = 4
 ; CHECK-SAME:  Latency=4
 
 ; CHECK-DEFAULT: VMLSS
 ; CHECK-FAST:    VFMSS
 ; CHECK:       Latency            : 9
 ; CHECK:       Successors:
 ; CHECK:       Data
 ; > VMLSS not-optimized latency to VMOVRS = 9

llvm/test/CodeGen/ARM/fp16-fullfp16.ll

; CHECK-NEXT:    bx lr
   ret void
 }
 
 define void @test_fmuladd(half* %p, half* %q, half* %r) {
 ; CHECK-LABEL: test_fmuladd:
 ; CHECK:         vldr.16 s0, [r1]
 ; CHECK-NEXT:    vldr.16 s2, [r0]
 ; CHECK-NEXT:    vldr.16 s4, [r2]
-; CHECK-NEXT:    vmla.f16 s4, s2, s0
+; CHECK-NEXT:    vfma.f16 s4, s2, s0
 ; CHECK-NEXT:    vstr.16 s4, [r0]
 ; CHECK-NEXT:    bx lr
   %a = load half, half* %p, align 2
   %b = load half, half* %q, align 2
   %c = load half, half* %r, align 2
   %v = call half @llvm.fmuladd.f16(half %a, half %b, half %c)
   store half %v, half* %p
   ret void

llvm/test/CodeGen/ARM/fp16-fusedMAC.ll

 ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
 ; RUN: llc < %s -mtriple=thumbv8.1-m-none-eabi -mattr=+fullfp16 -fp-contract=fast | FileCheck %s
-; RUN: llc < %s -mtriple=thumbv8.1-m-none-eabi -mattr=+fullfp16,+slowfpvmlx -fp-contract=fast | FileCheck %s -check-prefix=DONT-FUSE
+; RUN: llc < %s -mtriple=thumbv8.1-m-none-eabi -mattr=+fullfp16,+slowfpvfmx -fp-contract=fast | FileCheck %s -check-prefix=DONT-FUSE
 
 ; Check generated fp16 fused MAC and MLS.
 
 define arm_aapcs_vfpcc void @fusedMACTest2(half *%a1, half *%a2, half *%a3) {
 ; CHECK-LABEL: fusedMACTest2:
 ; CHECK:       @ %bb.0:
 ; CHECK-NEXT:    vldr.16 s0, [r1]
 ; CHECK-NEXT:    vldr.16 s2, [r0]

llvm/test/CodeGen/Thumb2/float-intrinsics-double.ll

 
 declare double     @llvm.fmuladd.f64(double %a, double %b, double %c)
 define double @fmuladd_d(double %a, double %b, double %c) {
 ; CHECK-LABEL: fmuladd_d:
 ; SOFT: bl __aeabi_dmul
 ; SOFT: bl __aeabi_dadd
 ; VFP4: vmul.f64
 ; VFP4: vadd.f64
-; FP-ARMv8: vmla.f64
+; FP-ARMv8: vfma.f64
   %1 = call double @llvm.fmuladd.f64(double %a, double %b, double %c)
   ret double %1
 }
 
 declare i16 @llvm.convert.to.fp16.f64(double %a)
 define i16 @d_to_h(double %a) {
 ; CHECK-LABEL: d_to_h:
 ; SOFT: bl __aeabi_d2h

llvm/test/CodeGen/Thumb2/float-intrinsics-float.ll

; FP-ARMv8: vrinta.f32
   ret float %1
 }
 
 declare float     @llvm.fmuladd.f32(float %a, float %b, float %c)
 define float @fmuladd_f(float %a, float %b, float %c) {
 ; CHECK-LABEL: fmuladd_f:
 ; SOFT: bl __aeabi_fmul
 ; SOFT: bl __aeabi_fadd
-; VMLA: vmla.f32
+; VMLA: vfma.f32
 ; NO-VMLA: vmul.f32
 ; NO-VMLA: vadd.f32
   %1 = call float @llvm.fmuladd.f32(float %a, float %b, float %c)
   ret float %1
 }
 
 declare i16 @llvm.convert.to.fp16.f32(float %a)
 define i16 @f_to_h(float %a) {