[ARM] Fix codegen for VLD3/VLD4/VST3/VST4 with WB

[thopre]

Summary

Code generation of VLD3, VLD4, VST3 and VST4 with register writeback is
broken due to 2 separate bugs:

1. VLD1d64TPseudoWB_register and VLD1d64QPseudoWB_register are missing rules to expand them to non pseudo MIR. These are selected for ARMISD::VLD3_UPD/VLD4_UPD with v1i64 vectors in SelectVLD.

2. Selection of the right VLD/VST instruction is broken for load and store of 3 and 4 v1i64 vectors. SelectVLD and SelectVST are called with MIR opcode for fixed writeback (ie increment is access size) and call getVLDSTRegisterUpdateOpcode() to select an opcode with register writeback if base register update is of a different size. Since getVLDSTRegisterUpdateOpcode() only knows about VLD1/VLD2/VST1/VST2 the call is currently conditional on the number of element in the vector.
   
   However, VLD1/VST1 is selected by SelectVLD/SelectVST's caller for load and stores of 3 or 4 v1i64 vectors. Therefore the opcode is not updated which later lead to a fixed writeback instruction being constructed with an extra operand for the register writeback.

This patch addresses the two issues as follows:

• it adds the necessary mapping from VLD1d64TPseudoWB_register and VLD1d64QPseudoWB_register to VLD1d64Twb_register and VLD1d64Qwb_register respectively. Like for the existing _fixed variants, the cost of these is bumped for unaligned access.
• it changes the logic in SelectVLD and SelectVSD to call isVLDfixed and isVSTfixed respectively to decide whether the opcode should be updated. It also reworks the logic and comments for pushing the writeback offset operand and r0 operand to clarify the logic: writeback offset needs to be pushed if it's a register writeback, r0 needs to be pushed if not and the instruction is a VLD1/VLD2/VST1/VST2.

[samparker]

test/CodeGen/ARM/pr35157.ll

7

I can see that the bug originally caused a fault, but we should also be testing what code is generated.

[thopre]

Extend existing vld3.ll/vld4.ll/vst3.ll/vst4.ll testcases instead of creating a new one, following similar patterns as those already in there incl. check directives.

[srhines]

https://reviews.llvm.org/D42967 is blocking this, but it would be great to get this into our next toolchain update.

[samparker]

Thanks for the changes, LGTM.

[thopre]

Merge patch with the one in https://reviews.llvm.org/D42967 and remove redundant mir test.

[samparker]

LGTM, thanks.

[thopre]

https://reviews.llvm.org/D42967 has been merged into this patch. Can I get a review of the new diff? Thanks!

[srhines]

Is this waiting on anything else? It looks like the approval happened at the same time as your last message.

[thopre]

In D42970#1024383, @srhines wrote:

Is this waiting on anything else? It looks like the approval happened at the same time as your last message.

Oh indeed, I thought the previous revision had been approved. I'll go ask for commit access and commit it asap.

[srhines]

LGTM. Thanks for fixing this and thanks to samparker for reviewing and fhahn submitting it.

lib/Target/ARM/ARMISelDAGToDAG.cpp

void ARMDAGToDAGISel::SelectVLD(SDNode *N, bool isUpdating, unsigned NumVecs,
   // Double registers and VLD1/VLD2 quad registers are directly supported.
   if (is64BitVector || NumVecs <= 2) {
     unsigned Opc = (is64BitVector ? DOpcodes[OpcodeIndex] :
                     QOpcodes0[OpcodeIndex]);
     Ops.push_back(MemAddr);
     Ops.push_back(Align);
     if (isUpdating) {
       SDValue Inc = N->getOperand(AddrOpIdx + 1);
-      // FIXME: VLD1/VLD2 fixed increment doesn't need Reg0. Remove the reg0
-      // case entirely when the rest are updated to that form, too.
       bool IsImmUpdate = isPerfectIncrement(Inc, VT, NumVecs);
-      if ((NumVecs <= 2) && !IsImmUpdate)
+      if (!IsImmUpdate) {
+        // We use a VLD1 for v1i64 even if the pseudo says vld2/3/4, so
+        // check for the opcode rather than the number of vector elements.
+        if (isVLDfixed(Opc))
           Opc = getVLDSTRegisterUpdateOpcode(Opc);
-      // FIXME: We use a VLD1 for v1i64 even if the pseudo says vld2/3/4, so
-      // check for that explicitly too. Horribly hacky, but temporary.
-      if ((NumVecs > 2 && !isVLDfixed(Opc)) || !IsImmUpdate)
-        Ops.push_back(IsImmUpdate ? Reg0 : Inc);
+        Ops.push_back(Inc);
+      // VLD1/VLD2 fixed increment does not need Reg0 so only include it in
+      // the operands if not such an opcode.
+      } else if (!isVLDfixed(Opc))
+        Ops.push_back(Reg0);
     }
     Ops.push_back(Pred);
     Ops.push_back(Reg0);
     Ops.push_back(Chain);
     VLd = CurDAG->getMachineNode(Opc, dl, ResTys, Ops);
 
   } else {
     // Otherwise, quad registers are loaded with two separate instructions,
if (is64BitVector || NumVecs <= 2) {
     }
 
     unsigned Opc = (is64BitVector ? DOpcodes[OpcodeIndex] :
                     QOpcodes0[OpcodeIndex]);
     Ops.push_back(MemAddr);
     Ops.push_back(Align);
     if (isUpdating) {
       SDValue Inc = N->getOperand(AddrOpIdx + 1);
-      // FIXME: VST1/VST2 fixed increment doesn't need Reg0. Remove the reg0
-      // case entirely when the rest are updated to that form, too.
       bool IsImmUpdate = isPerfectIncrement(Inc, VT, NumVecs);
-      if (NumVecs <= 2 && !IsImmUpdate)
+      if (!IsImmUpdate) {
+        // We use a VST1 for v1i64 even if the pseudo says VST2/3/4, so
+        // check for the opcode rather than the number of vector elements.
+        if (isVSTfixed(Opc))
           Opc = getVLDSTRegisterUpdateOpcode(Opc);
-      // FIXME: We use a VST1 for v1i64 even if the pseudo says vld2/3/4, so
-      // check for that explicitly too. Horribly hacky, but temporary.
-      if  (!IsImmUpdate)
         Ops.push_back(Inc);
-      else if (NumVecs > 2 && !isVSTfixed(Opc))
+      }
+      // VST1/VST2 fixed increment does not need Reg0 so only include it in
+      // the operands if not such an opcode.
+      else if (!isVSTfixed(Opc))
         Ops.push_back(Reg0);
     }
     Ops.push_back(SrcReg);
     Ops.push_back(Pred);
     Ops.push_back(Reg0);
     Ops.push_back(Chain);
     SDNode *VSt = CurDAG->getMachineNode(Opc, dl, ResTys, Ops);
 

test/CodeGen/ARM/pr35157.ll

+; RUN: llc -mtriple armv7 -start-after=verify < %s
+
+target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"
+
+%struct.__neon_int64x1x3_t = type { <1 x i64>, <1 x i64>, <1 x i64> }
+%struct.__neon_int64x1x4_t = type { <1 x i64>, <1 x i64>, <1 x i64>, <1 x i64> }
+
+define <1 x i64> @vld3i64(i8* %A, i8** %B) nounwind {
+  %1 = call %struct.__neon_int64x1x3_t @llvm.arm.neon.vld3.v1i64.p0i8(i8* %A, i32 8)
+  %2 = getelementptr i8, i8* %A, i32 4
+  store i8* %2, i8** %B
+  %3 = extractvalue %struct.__neon_int64x1x3_t %1, 0
+  ret <1 x i64> %3
+}
+
+define <1 x i64> @vld4i64(i8* %A, i8** %B) nounwind {
+  %1 = call %struct.__neon_int64x1x4_t @llvm.arm.neon.vld4.v1i64.p0i8(i8* %A, i32 8)
+  %2 = getelementptr i8, i8* %A, i32 4
+  store i8* %2, i8** %B
+  %3 = extractvalue %struct.__neon_int64x1x4_t %1, 0
+  ret <1 x i64> %3
+}
+
+define i8* @vst3i64_wb(i8* %A, <1 x i64>* %B) nounwind {
+  %1 = load <1 x i64>, <1 x i64>* %B
+  call void @llvm.arm.neon.vst3.p0i8.v1i64(i8* %A, <1 x i64> %1, <1 x i64> %1, <1 x i64> %1, i32 4)
+  %2 = getelementptr i8, i8* %A, i32 4
+  ret i8* %2
+}
+
+define i8* @vst4i64_wb(i8* %A, <1 x i64>* %B) nounwind {
+  %1 = load <1 x i64>, <1 x i64>* %B
+  call void @llvm.arm.neon.vst4.p0i8.v1i64(i8* %A, <1 x i64> %1, <1 x i64> %1, <1 x i64> %1, <1 x i64> %1, i32 4)
+  %2 = getelementptr i8, i8* %A, i32 4
+  ret i8* %2
+}
+
+; Function Attrs: argmemonly nounwind
+declare %struct.__neon_int64x1x3_t @llvm.arm.neon.vld3.v1i64.p0i8(i8*, i32) nounwind readonly
+declare %struct.__neon_int64x1x4_t @llvm.arm.neon.vld4.v1i64.p0i8(i8*, i32) nounwind readonly
+declare void @llvm.arm.neon.vst3.p0i8.v1i64(i8*, <1 x i64>, <1 x i64>, <1 x i64>, i32) #1
+declare void @llvm.arm.neon.vst4.p0i8.v1i64(i8*, <1 x i64>, <1 x i64>, <1 x i64>, <1 x i64>, i32) #1
+
+attributes #0 = { noinline nounwind optnone "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="cortex-a7" "target-features"="+dsp,+hwdiv,+hwdiv-arm,+neon,+vfp4,-crc,-dotprod,-ras,-thumb-mode" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #1 = { argmemonly nounwind }