AMDGPU: Convert vector 64-bit shl to 32-bit if shift amt >= 32 (#132964)

Convert vector 64-bit shl to 32-bit if shift amt is known to be >= 32.

---------

Signed-off-by: John Lu <[email protected]>

Author: LU-JOHN

llvm/lib/Target/AMDGPU/AMDGPUISelLowering.cpp

@@ -4084,29 +4084,32 @@ SDValue AMDGPUTargetLowering::performShlCombine(SDNode *N,
     }
   }
 
-  if (VT != MVT::i64)
+  if (VT.getScalarType() != MVT::i64)
     return SDValue();
 
   // i64 (shl x, C) -> (build_pair 0, (shl x, C -32))
 
   // On some subtargets, 64-bit shift is a quarter rate instruction. In the
   // common case, splitting this into a move and a 32-bit shift is faster and
   // the same code size.
-  EVT TargetType = VT.getHalfSizedIntegerVT(*DAG.getContext());
-  EVT TargetVecPairType = EVT::getVectorVT(*DAG.getContext(), TargetType, 2);
   KnownBits Known = DAG.computeKnownBits(RHS);
 
-  if (Known.getMinValue().getZExtValue() < TargetType.getSizeInBits())
+  EVT ElementType = VT.getScalarType();
+  EVT TargetScalarType = ElementType.getHalfSizedIntegerVT(*DAG.getContext());
+  EVT TargetType = VT.isVector() ? VT.changeVectorElementType(TargetScalarType)
+                                 : TargetScalarType;
+
+  if (Known.getMinValue().getZExtValue() < TargetScalarType.getSizeInBits())
     return SDValue();
   SDValue ShiftAmt;
 
   if (CRHS) {
-    ShiftAmt =
-        DAG.getConstant(RHSVal - TargetType.getSizeInBits(), SL, TargetType);
+    ShiftAmt = DAG.getConstant(RHSVal - TargetScalarType.getSizeInBits(), SL,
+                               TargetType);
   } else {
     SDValue truncShiftAmt = DAG.getNode(ISD::TRUNCATE, SL, TargetType, RHS);
     const SDValue ShiftMask =
-        DAG.getConstant(TargetType.getSizeInBits() - 1, SL, TargetType);
+        DAG.getConstant(TargetScalarType.getSizeInBits() - 1, SL, TargetType);
     // This AND instruction will clamp out of bounds shift values.
     // It will also be removed during later instruction selection.
     ShiftAmt = DAG.getNode(ISD::AND, SL, TargetType, truncShiftAmt, ShiftMask);
@@ -4116,9 +4119,23 @@ SDValue AMDGPUTargetLowering::performShlCombine(SDNode *N,
   SDValue NewShift =
       DAG.getNode(ISD::SHL, SL, TargetType, Lo, ShiftAmt, N->getFlags());
 
-  const SDValue Zero = DAG.getConstant(0, SL, TargetType);
+  const SDValue Zero = DAG.getConstant(0, SL, TargetScalarType);
+  SDValue Vec;
 
-  SDValue Vec = DAG.getBuildVector(TargetVecPairType, SL, {Zero, NewShift});
+  if (VT.isVector()) {
+    EVT ConcatType = TargetType.getDoubleNumVectorElementsVT(*DAG.getContext());
+    unsigned NElts = TargetType.getVectorNumElements();
+    SmallVector<SDValue, 8> HiOps;
+    SmallVector<SDValue, 16> HiAndLoOps(NElts * 2, Zero);
+
+    DAG.ExtractVectorElements(NewShift, HiOps, 0, NElts);
+    for (unsigned I = 0; I != NElts; ++I)
+      HiAndLoOps[2 * I + 1] = HiOps[I];
+    Vec = DAG.getNode(ISD::BUILD_VECTOR, SL, ConcatType, HiAndLoOps);
+  } else {
+    EVT ConcatType = EVT::getVectorVT(*DAG.getContext(), TargetType, 2);
+    Vec = DAG.getBuildVector(ConcatType, SL, {Zero, NewShift});
+  }
   return DAG.getNode(ISD::BITCAST, SL, VT, Vec);
 }
 
@@ -5182,9 +5199,14 @@ SDValue AMDGPUTargetLowering::PerformDAGCombine(SDNode *N,
     break;
   }
   case ISD::SHL: {
-    if (DCI.getDAGCombineLevel() < AfterLegalizeDAG)
+    // Range metadata can be invalidated when loads are converted to legal types
+    // (e.g. v2i64 -> v4i32).
+    // Try to convert vector shl before type legalization so that range metadata
+    // can be utilized.
+    if (!(N->getValueType(0).isVector() &&
+          DCI.getDAGCombineLevel() == BeforeLegalizeTypes) &&
+        DCI.getDAGCombineLevel() < AfterLegalizeDAG)
       break;
-
     return performShlCombine(N, DCI);
   }
   case ISD::SRL: {

llvm/test/CodeGen/AMDGPU/shl64_reduce.ll

@@ -72,39 +72,41 @@ define i64 @shl_metadata_cant_be_narrowed_to_i32(i64 %arg0, ptr %arg1.ptr) {
   ret i64 %shl
 }
 
-; FIXME: This case should be reduced
 define <2 x i64> @shl_v2_metadata(<2 x i64> %arg0, ptr %arg1.ptr) {
 ; CHECK-LABEL: shl_v2_metadata:
 ; CHECK:       ; %bb.0:
 ; CHECK-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
-; CHECK-NEXT:    flat_load_dwordx4 v[4:7], v[4:5]
+; CHECK-NEXT:    flat_load_dwordx4 v[3:6], v[4:5]
 ; CHECK-NEXT:    s_waitcnt vmcnt(0) lgkmcnt(0)
-; CHECK-NEXT:    v_lshlrev_b64 v[0:1], v4, v[0:1]
-; CHECK-NEXT:    v_lshlrev_b64 v[2:3], v6, v[2:3]
+; CHECK-NEXT:    v_lshlrev_b32_e32 v1, v3, v0
+; CHECK-NEXT:    v_lshlrev_b32_e32 v3, v5, v2
+; CHECK-NEXT:    v_mov_b32_e32 v0, 0
+; CHECK-NEXT:    v_mov_b32_e32 v2, 0
 ; CHECK-NEXT:    s_setpc_b64 s[30:31]
   %shift.amt = load <2 x i64>, ptr %arg1.ptr, !range !0, !noundef !{}
   %shl = shl <2 x i64> %arg0, %shift.amt
   ret <2 x i64> %shl
 }
 
-; FIXME: This case should be reduced
 define <3 x i64> @shl_v3_metadata(<3 x i64> %arg0, ptr %arg1.ptr) {
 ; CHECK-LABEL: shl_v3_metadata:
 ; CHECK:       ; %bb.0:
 ; CHECK-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
-; CHECK-NEXT:    flat_load_dword v12, v[6:7] offset:16
+; CHECK-NEXT:    flat_load_dword v1, v[6:7] offset:16
 ; CHECK-NEXT:    flat_load_dwordx4 v[8:11], v[6:7]
 ; CHECK-NEXT:    s_waitcnt vmcnt(0) lgkmcnt(0)
-; CHECK-NEXT:    v_lshlrev_b64 v[4:5], v12, v[4:5]
-; CHECK-NEXT:    v_lshlrev_b64 v[0:1], v8, v[0:1]
-; CHECK-NEXT:    v_lshlrev_b64 v[2:3], v10, v[2:3]
+; CHECK-NEXT:    v_lshlrev_b32_e32 v5, v1, v4
+; CHECK-NEXT:    v_lshlrev_b32_e32 v1, v8, v0
+; CHECK-NEXT:    v_lshlrev_b32_e32 v3, v10, v2
+; CHECK-NEXT:    v_mov_b32_e32 v0, 0
+; CHECK-NEXT:    v_mov_b32_e32 v2, 0
+; CHECK-NEXT:    v_mov_b32_e32 v4, 0
 ; CHECK-NEXT:    s_setpc_b64 s[30:31]
   %shift.amt = load <3 x i64>, ptr %arg1.ptr, !range !0, !noundef !{}
   %shl = shl <3 x i64> %arg0, %shift.amt
   ret <3 x i64> %shl
 }
 
-; FIXME: This case should be reduced
 define <4 x i64> @shl_v4_metadata(<4 x i64> %arg0, ptr %arg1.ptr) {
 ; CHECK-LABEL: shl_v4_metadata:
 ; CHECK:       ; %bb.0:
@@ -113,11 +115,15 @@ define <4 x i64> @shl_v4_metadata(<4 x i64> %arg0, ptr %arg1.ptr) {
 ; CHECK-NEXT:    s_waitcnt vmcnt(0) lgkmcnt(0)
 ; CHECK-NEXT:    flat_load_dwordx4 v[13:16], v[8:9] offset:16
 ; CHECK-NEXT:    ; kill: killed $vgpr8 killed $vgpr9
-; CHECK-NEXT:    v_lshlrev_b64 v[0:1], v10, v[0:1]
-; CHECK-NEXT:    v_lshlrev_b64 v[2:3], v12, v[2:3]
+; CHECK-NEXT:    v_lshlrev_b32_e32 v1, v10, v0
+; CHECK-NEXT:    v_lshlrev_b32_e32 v3, v12, v2
 ; CHECK-NEXT:    s_waitcnt vmcnt(0) lgkmcnt(0)
-; CHECK-NEXT:    v_lshlrev_b64 v[4:5], v13, v[4:5]
-; CHECK-NEXT:    v_lshlrev_b64 v[6:7], v15, v[6:7]
+; CHECK-NEXT:    v_lshlrev_b32_e32 v5, v13, v4
+; CHECK-NEXT:    v_lshlrev_b32_e32 v7, v15, v6
+; CHECK-NEXT:    v_mov_b32_e32 v0, 0
+; CHECK-NEXT:    v_mov_b32_e32 v2, 0
+; CHECK-NEXT:    v_mov_b32_e32 v4, 0
+; CHECK-NEXT:    v_mov_b32_e32 v6, 0
 ; CHECK-NEXT:    s_setpc_b64 s[30:31]
   %shift.amt = load <4 x i64>, ptr %arg1.ptr, !range !0, !noundef !{}
   %shl = shl <4 x i64> %arg0, %shift.amt