[ARM] Do not test for CPUs, use SubtargetFeatures. Also remove 1 flag

This is a follow-up for r273544.

The end goal is to get rid of the isSwift / isCortexXY / isWhatever methods.

This commit also removes a command line flag that isn't used in any of the tests:
check-vmlx-hazards. It can be replaced easily with the mattr mechanism, since
this is now a subtarget feature.

There is still some work left regarding FeatureExpandMLx. In the past MLx
expansion was enabled for subtargets with hasVFP2(), until r129775 [1] switched
from that to isCortexA9, without too much justification.

In spite of that, the code performing MLx expansion still contains calls to
isSwift/isLikeA9, although the results of those are pretty clear given that
we're only enabling it for the A9.

We should try to enable it for all targets that have FeatureHasVMLxHazards, as
it seems to be closely related to that behaviour, and if that is possible try to
clean up the MLx expansion pass from all calls to isWhatever. This will require
some performance testing, so it will be done in another patch.

[1] http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20110418/119725.html

Differential Revision: http://reviews.llvm.org/D21798

llvm-svn: 274742

llvm/lib/Target/ARM/ARM.td

@@ -150,6 +150,14 @@ def FeatureDontWidenVMOVS : SubtargetFeature<"dont-widen-vmovs",
                                              "DontWidenVMOVS", "true",
                                              "Don't widen VMOVS to VMOVD">;
 
+// Whether or not it is profitable to expand VFP/NEON MLA/MLS instructions.
+def FeatureExpandMLx : SubtargetFeature<"expand-fp-mlx", "ExpandMLx", "true",
+                                        "Expand VFP/NEON MLA/MLS instructions">;
+
+// Some targets have special RAW hazards for VFP/NEON VMLA/VMLS.
+def FeatureHasVMLxHazards : SubtargetFeature<"vmlx-hazards", "HasVMLxHazards",
+                                             "true", "Has VMLx hazards">;
+
 // Some targets (e.g. Cortex-A9) want to convert VMOVRS, VMOVSR and VMOVS from
 // VFP to NEON, as an execution domain optimization.
 def FeatureNEONForFPMovs : SubtargetFeature<"neon-fpmovs", "UseNEONForFPMovs",
@@ -570,6 +578,7 @@ def : ProcessorModel<"cortex-a7",   CortexA8Model,      [ARMv7a, ProcA7,
                                                          FeatureHasRetAddrStack,
                                                          FeatureTrustZone,
                                                          FeatureSlowFPBrcc,
+                                                         FeatureHasVMLxHazards,
                                                          FeatureHasSlowFPVMLx,
                                                          FeatureVMLxForwarding,
                                                          FeatureT2XtPk,
@@ -584,17 +593,20 @@ def : ProcessorModel<"cortex-a8",   CortexA8Model,      [ARMv7a, ProcA8,
                                                          FeatureNonpipelinedVFP,
                                                          FeatureTrustZone,
                                                          FeatureSlowFPBrcc,
+                                                         FeatureHasVMLxHazards,
                                                          FeatureHasSlowFPVMLx,
                                                          FeatureVMLxForwarding,
                                                          FeatureT2XtPk]>;
 
 def : ProcessorModel<"cortex-a9",   CortexA9Model,      [ARMv7a, ProcA9,
                                                          FeatureHasRetAddrStack,
                                                          FeatureTrustZone,
+                                                         FeatureHasVMLxHazards,
                                                          FeatureVMLxForwarding,
                                                          FeatureT2XtPk,
                                                          FeatureFP16,
                                                          FeatureAvoidPartialCPSR,
+                                                         FeatureExpandMLx,
                                                          FeaturePreferVMOVSR,
                                                          FeatureMuxedUnits,
                                                          FeatureNEONForFPMovs,
@@ -668,6 +680,7 @@ def : ProcessorModel<"swift",       SwiftModel,         [ARMv7a, ProcSwift,
                                                          FeatureAvoidPartialCPSR,
                                                          FeatureAvoidMOVsShOp,
                                                          FeatureHasSlowFPVMLx,
+                                                         FeatureHasVMLxHazards,
                                                          FeatureProfUnpredicate,
                                                          FeaturePrefISHSTBarrier,
                                                          FeatureSlowOddRegister,

llvm/lib/Target/ARM/ARMISelDAGToDAG.cpp

@@ -43,11 +43,6 @@ DisableShifterOp("disable-shifter-op", cl::Hidden,
   cl::desc("Disable isel of shifter-op"),
   cl::init(false));
 
-static cl::opt<bool>
-CheckVMLxHazard("check-vmlx-hazard", cl::Hidden,
-  cl::desc("Check fp vmla / vmls hazard at isel time"),
-  cl::init(true));
-
 //===--------------------------------------------------------------------===//
 /// ARMDAGToDAGISel - ARM specific code to select ARM machine
 /// instructions for SelectionDAG operations.
@@ -427,11 +422,7 @@ bool ARMDAGToDAGISel::hasNoVMLxHazardUse(SDNode *N) const {
   if (OptLevel == CodeGenOpt::None)
     return true;
 
-  if (!CheckVMLxHazard)
-    return true;
-
-  if (!Subtarget->isCortexA7() && !Subtarget->isCortexA8() &&
-      !Subtarget->isCortexA9() && !Subtarget->isSwift())
+  if (!Subtarget->hasVMLxHazards())
     return true;
 
   if (!N->hasOneUse())

llvm/lib/Target/ARM/ARMSubtarget.h

@@ -262,6 +262,12 @@ class ARMSubtarget : public ARMGenSubtargetInfo {
   /// If true, VMOVS will never be widened to VMOVD
   bool DontWidenVMOVS = false;
 
+  /// If true, run the MLx expansion pass.
+  bool ExpandMLx = false;
+
+  /// If true, VFP/NEON VMLA/VMLS have special RAW hazards.
+  bool HasVMLxHazards = false;
+
   /// If true, VMOVRS, VMOVSR and VMOVS will be converted from VFP to NEON.
   bool UseNEONForFPMovs = false;
 
@@ -451,6 +457,8 @@ class ARMSubtarget : public ARMGenSubtargetInfo {
   bool hasSlowVDUP32() const { return HasSlowVDUP32; }
   bool preferVMOVSR() const { return PreferVMOVSR; }
   bool preferISHSTBarriers() const { return PreferISHST; }
+  bool expandMLx() const { return ExpandMLx; }
+  bool hasVMLxHazards() const { return HasVMLxHazards; }
   bool hasSlowOddRegister() const { return SlowOddRegister; }
   bool hasSlowLoadDSubregister() const { return SlowLoadDSubregister; }
   bool hasMuxedUnits() const { return HasMuxedUnits; }

llvm/lib/Target/ARM/MLxExpansionPass.cpp

@@ -385,8 +385,7 @@ bool MLxExpansion::runOnMachineFunction(MachineFunction &Fn) {
   TRI = Fn.getSubtarget().getRegisterInfo();
   MRI = &Fn.getRegInfo();
   const ARMSubtarget *STI = &Fn.getSubtarget<ARMSubtarget>();
-  // Only run this for CortexA9.
-  if (!STI->isCortexA9())
+  if (!STI->expandMLx())
     return false;
   isLikeA9 = STI->isLikeA9() || STI->isSwift();
   isSwift = STI->isSwift();