[llvm] [ARM][NEON] Add constraint to vld2 Odd/Even Pseudo instructions. (PR #79287)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-backend-arm

Author: Alfie Richards (AlfieRichardsArm)

<details>
<summary>Changes</summary>

This ensures the odd/even pseudo instructions are allocated to the same register range.

This fixes #<!-- -->71763 (https://github.com/llvm/llvm-project/issues/71763)

---
Full diff: https://github.com/llvm/llvm-project/pull/79287.diff


4 Files Affected:

- (modified) llvm/lib/Target/ARM/ARMExpandPseudoInsts.cpp (+3-6) 
- (modified) llvm/lib/Target/ARM/ARMISelDAGToDAG.cpp (-5) 
- (modified) llvm/lib/Target/ARM/ARMInstrNEON.td (+26-12) 
- (modified) llvm/test/CodeGen/ARM/bf16-intrinsics-ld-st.ll (+1-1) 


``````````diff
diff --git a/llvm/lib/Target/ARM/ARMExpandPseudoInsts.cpp b/llvm/lib/Target/ARM/ARMExpandPseudoInsts.cpp
index 2f9236bb977fc9..f0b69b0b09809f 100644
--- a/llvm/lib/Target/ARM/ARMExpandPseudoInsts.cpp
+++ b/llvm/lib/Target/ARM/ARMExpandPseudoInsts.cpp
@@ -640,12 +640,9 @@ void ARMExpandPseudo::ExpandVLD(MachineBasicBlock::iterator &MBBI) {
   // has an extra operand that is a use of the super-register.  Record the
   // operand index and skip over it.
   unsigned SrcOpIdx = 0;
-  if (!IsVLD2DUP) {
-    if (RegSpc == EvenDblSpc || RegSpc == OddDblSpc ||
-        RegSpc == SingleLowSpc || RegSpc == SingleHighQSpc ||
-        RegSpc == SingleHighTSpc)
-      SrcOpIdx = OpIdx++;
-  }
+  if (RegSpc == EvenDblSpc || RegSpc == OddDblSpc || RegSpc == SingleLowSpc ||
+      RegSpc == SingleHighQSpc || RegSpc == SingleHighTSpc)
+    SrcOpIdx = OpIdx++;
 
   // Copy the predicate operands.
   MIB.add(MI.getOperand(OpIdx++));
diff --git a/llvm/lib/Target/ARM/ARMISelDAGToDAG.cpp b/llvm/lib/Target/ARM/ARMISelDAGToDAG.cpp
index e99ee299412a5f..20dd3e7baf8498 100644
--- a/llvm/lib/Target/ARM/ARMISelDAGToDAG.cpp
+++ b/llvm/lib/Target/ARM/ARMISelDAGToDAG.cpp
@@ -3032,11 +3032,6 @@ void ARMDAGToDAGISel::SelectVLDDup(SDNode *N, bool IsIntrinsic,
   }
   if (is64BitVector || NumVecs == 1) {
     // Double registers and VLD1 quad registers are directly supported.
-  } else if (NumVecs == 2) {
-    const SDValue OpsA[] = {MemAddr, Align, Pred, Reg0, Chain};
-    SDNode *VLdA = CurDAG->getMachineNode(QOpcodes0[OpcodeIndex], dl, ResTy,
-                                          MVT::Other, OpsA);
-    Chain = SDValue(VLdA, 1);
   } else {
     SDValue ImplDef = SDValue(
         CurDAG->getMachineNode(TargetOpcode::IMPLICIT_DEF, dl, ResTy), 0);
diff --git a/llvm/lib/Target/ARM/ARMInstrNEON.td b/llvm/lib/Target/ARM/ARMInstrNEON.td
index f31e1e9f97892f..e7cf8b4657b2c8 100644
--- a/llvm/lib/Target/ARM/ARMInstrNEON.td
+++ b/llvm/lib/Target/ARM/ARMInstrNEON.td
@@ -1491,12 +1491,26 @@ def VLD2DUPd16x2 : VLD2DUP<{0,1,1,?}, "16", VecListDPairSpacedAllLanes,
 def VLD2DUPd32x2 : VLD2DUP<{1,0,1,?}, "32", VecListDPairSpacedAllLanes,
                            addrmode6dupalign64>;
 
-def VLD2DUPq8EvenPseudo  : VLDQQPseudo<IIC_VLD2dup>, Sched<[WriteVLD2]>;
-def VLD2DUPq8OddPseudo   : VLDQQPseudo<IIC_VLD2dup>, Sched<[WriteVLD2]>;
-def VLD2DUPq16EvenPseudo : VLDQQPseudo<IIC_VLD2dup>, Sched<[WriteVLD2]>;
-def VLD2DUPq16OddPseudo  : VLDQQPseudo<IIC_VLD2dup>, Sched<[WriteVLD2]>;
-def VLD2DUPq32EvenPseudo : VLDQQPseudo<IIC_VLD2dup>, Sched<[WriteVLD2]>;
-def VLD2DUPq32OddPseudo  : VLDQQPseudo<IIC_VLD2dup>, Sched<[WriteVLD2]>;
+// Duplicate of VLDQQPseudo but with a constraint variable
+// to ensure the odd and even lanes use the same register range 
+class VLDQQPseudoConstrained<InstrItinClass itin>
+  : PseudoNLdSt<(outs QQPR:$dst), (ins addrmode6:$addr, QQPR: $src), itin, 
+                "$src = $dst">;
+class VLDQQWBPseudoConstrained<InstrItinClass itin>
+  : PseudoNLdSt<(outs QQPR:$dst, GPR:$wb),
+                (ins addrmode6:$addr, am6offset:$offset, QQPR: $src), itin,
+                "$addr.addr = $wb, $src = $dst">;
+class VLDQQWBfixedPseudoConstrained<InstrItinClass itin>
+  : PseudoNLdSt<(outs QQPR:$dst, GPR:$wb),
+                (ins addrmode6:$addr, QQPR: $src), itin,
+                "$addr.addr = $wb, $src = $dst">;
+
+def VLD2DUPq8EvenPseudo  : VLDQQPseudoConstrained<IIC_VLD2dup>, Sched<[WriteVLD2]>;
+def VLD2DUPq8OddPseudo   : VLDQQPseudoConstrained<IIC_VLD2dup>, Sched<[WriteVLD2]>;
+def VLD2DUPq16EvenPseudo : VLDQQPseudoConstrained<IIC_VLD2dup>, Sched<[WriteVLD2]>;
+def VLD2DUPq16OddPseudo  : VLDQQPseudoConstrained<IIC_VLD2dup>, Sched<[WriteVLD2]>;
+def VLD2DUPq32EvenPseudo : VLDQQPseudoConstrained<IIC_VLD2dup>, Sched<[WriteVLD2]>;
+def VLD2DUPq32OddPseudo  : VLDQQPseudoConstrained<IIC_VLD2dup>, Sched<[WriteVLD2]>;
 
 // ...with address register writeback:
 multiclass VLD2DUPWB<bits<4> op7_4, string Dt, RegisterOperand VdTy,
@@ -1534,12 +1548,12 @@ defm VLD2DUPd16x2wb : VLD2DUPWB<{0,1,1,?}, "16", VecListDPairSpacedAllLanes,
 defm VLD2DUPd32x2wb : VLD2DUPWB<{1,0,1,?}, "32", VecListDPairSpacedAllLanes,
                                 addrmode6dupalign64>;
 
-def VLD2DUPq8OddPseudoWB_fixed     : VLDQQWBfixedPseudo<IIC_VLD2dup>, Sched<[WriteVLD2]>;
-def VLD2DUPq16OddPseudoWB_fixed    : VLDQQWBfixedPseudo<IIC_VLD2dup>, Sched<[WriteVLD2]>;
-def VLD2DUPq32OddPseudoWB_fixed    : VLDQQWBfixedPseudo<IIC_VLD2dup>, Sched<[WriteVLD2]>;
-def VLD2DUPq8OddPseudoWB_register  : VLDQQWBPseudo<IIC_VLD2dup>, Sched<[WriteVLD2]>;
-def VLD2DUPq16OddPseudoWB_register : VLDQQWBPseudo<IIC_VLD2dup>, Sched<[WriteVLD2]>;
-def VLD2DUPq32OddPseudoWB_register : VLDQQWBPseudo<IIC_VLD2dup>, Sched<[WriteVLD2]>;
+def VLD2DUPq8OddPseudoWB_fixed     : VLDQQWBfixedPseudoConstrained<IIC_VLD2dup>, Sched<[WriteVLD2]>;
+def VLD2DUPq16OddPseudoWB_fixed    : VLDQQWBfixedPseudoConstrained<IIC_VLD2dup>, Sched<[WriteVLD2]>;
+def VLD2DUPq32OddPseudoWB_fixed    : VLDQQWBfixedPseudoConstrained<IIC_VLD2dup>, Sched<[WriteVLD2]>;
+def VLD2DUPq8OddPseudoWB_register  : VLDQQWBPseudoConstrained<IIC_VLD2dup>, Sched<[WriteVLD2]>;
+def VLD2DUPq16OddPseudoWB_register : VLDQQWBPseudoConstrained<IIC_VLD2dup>, Sched<[WriteVLD2]>;
+def VLD2DUPq32OddPseudoWB_register : VLDQQWBPseudoConstrained<IIC_VLD2dup>, Sched<[WriteVLD2]>;
 
 //   VLD3DUP  : Vector Load (single 3-element structure to all lanes)
 class VLD3DUP<bits<4> op7_4, string Dt>
diff --git a/llvm/test/CodeGen/ARM/bf16-intrinsics-ld-st.ll b/llvm/test/CodeGen/ARM/bf16-intrinsics-ld-st.ll
index cccbdd04357650..e49128f53b1157 100644
--- a/llvm/test/CodeGen/ARM/bf16-intrinsics-ld-st.ll
+++ b/llvm/test/CodeGen/ARM/bf16-intrinsics-ld-st.ll
@@ -488,7 +488,7 @@ entry:
 define arm_aapcs_vfpcc [2 x <4 x i32>] @test_vld2q_dup_bf16(ptr %ptr) {
 ; CHECK-LABEL: test_vld2q_dup_bf16:
 ; CHECK:       @ %bb.0: @ %entry
-; CHECK-NEXT:    vld2.16 {d16[], d18[]}, [r0]
+; CHECK-NEXT:    vld2.16 {d0[], d2[]}, [r0]
 ; CHECK-NEXT:    vld2.16 {d1[], d3[]}, [r0]
 ; CHECK-NEXT:    bx lr
 entry:

``````````

</details>


https://github.com/llvm/llvm-project/pull/79287