[ARM][MVE] Tail predicate VML[A|S]LDAV

Make the non-exchanging versions of the multiply add/sub instructions
validForTailPredication.

Differential Revision: https://reviews.llvm.org/D77648

Author: sparker-arm

llvm/lib/Target/ARM/ARMInstrMVE.td

@@ -909,6 +909,11 @@ class MVE_VMLAMLSDAV<string iname, string suffix, dag iops, string cstr,
   let Inst{3-1} = Qm{2-0};
   let Inst{0} = bit_0;
   let horizontalReduction = 1;
+  // Allow tail predication for non-exchanging versions. As this is also a
+  // horizontalReduction, ARMLowOverheadLoops will also have to check that
+  // the vector operands contain zeros in their false lanes for the instruction
+  // to be properly valid.
+  let validForTailPredication = !eq(X, 0);
 }
 
 multiclass MVE_VMLAMLSDAV_A<string iname, string x, MVEVectorVTInfo VTI,
@@ -1068,6 +1073,11 @@ class MVE_VMLALDAVBase<string iname, string suffix, dag iops, string cstr,
   let Inst{3-1} = Qm{2-0};
   let Inst{0} = bit_0;
   let horizontalReduction = 1;
+  // Allow tail predication for non-exchanging versions. As this is also a
+  // horizontalReduction, ARMLowOverheadLoops will also have to check that
+  // the vector operands contain zeros in their false lanes for the instruction
+  // to be properly valid.
+  let validForTailPredication = !eq(X, 0);
 
   let hasSideEffects = 0;
 }

llvm/lib/Target/ARM/MCTargetDesc/ARMBaseInfo.h

@@ -393,7 +393,8 @@ namespace ARMII {
     // in an IT block).
     ThumbArithFlagSetting = 1 << 19,
 
-    // Whether an instruction can be included in an MVE tail-predicated loop.
+    // Whether an instruction can be included in an MVE tail-predicated loop,
+    // though extra validity checks may need to be performed too.
     ValidForTailPredication = 1 << 20,
 
     // Whether an instruction writes to the top/bottom half of a vector element

llvm/unittests/Target/ARM/MachineInstrTest.cpp

@@ -368,7 +368,7 @@ TEST(MachineInstructionRetainsPreviousHalfElement, IsCorrect) {
 // descriptions. Currently we, conservatively, disallow:
 // - cross beat carries.
 // - complex operations.
-// - horizontal operations.
+// - horizontal operations with exchange.
 // - byte swapping.
 // - interleaved memory instructions.
 // TODO: Add to this list once we can handle them safely.
@@ -531,6 +531,42 @@ TEST(MachineInstrValidTailPredication, IsCorrect) {
     case MVE_VMINu16:
     case MVE_VMINu32:
     case MVE_VMINu8:
+    case MVE_VMLADAVas16:
+    case MVE_VMLADAVas32:
+    case MVE_VMLADAVas8:
+    case MVE_VMLADAVau16:
+    case MVE_VMLADAVau32:
+    case MVE_VMLADAVau8:
+    case MVE_VMLADAVs16:
+    case MVE_VMLADAVs32:
+    case MVE_VMLADAVs8:
+    case MVE_VMLADAVu16:
+    case MVE_VMLADAVu32:
+    case MVE_VMLADAVu8:
+    case MVE_VMLALDAVs16:
+    case MVE_VMLALDAVs32:
+    case MVE_VMLALDAVu16:
+    case MVE_VMLALDAVu32:
+    case MVE_VMLALDAVas16:
+    case MVE_VMLALDAVas32:
+    case MVE_VMLALDAVau16:
+    case MVE_VMLALDAVau32:
+    case MVE_VMLSDAVas16:
+    case MVE_VMLSDAVas32:
+    case MVE_VMLSDAVas8:
+    case MVE_VMLSDAVs16:
+    case MVE_VMLSDAVs32:
+    case MVE_VMLSDAVs8:
+    case MVE_VMLSLDAVas16:
+    case MVE_VMLSLDAVas32:
+    case MVE_VMLSLDAVs16:
+    case MVE_VMLSLDAVs32:
+    case MVE_VRMLALDAVHas32:
+    case MVE_VRMLALDAVHau32:
+    case MVE_VRMLALDAVHs32:
+    case MVE_VRMLALDAVHu32:
+    case MVE_VRMLSLDAVHas32:
+    case MVE_VRMLSLDAVHs32:
     case MVE_VMLAS_qr_s16:
     case MVE_VMLAS_qr_s32:
     case MVE_VMLAS_qr_s8: