[PATCH] D42407: [X86] Use ISD::SIGN_EXTEND instead of X86ISD::VSEXT for mask to xmm/ymm/zmm conversion

[Craig Topper via Phabricator via llvm-commits]

craig.topper created this revision.
craig.topper added reviewers: RKSimon, spatel.
Herald added a subscriber: rengolin.

There are a couple tricky things with this patch.

I had to add an override of isVectorLoadExtDesirable to stop DAG combine from combining sign_extend with loads after legalization since we legalize sextload using a load+sign_extend. Overriding this hook actually prevents a lot sextloads from being created in the first place.

I also had to add isel patterns because DAG combine blindly combines sign_extend+truncate to a smaller sign_extend which defeats what legalization was trying to do.

This patch also requires the v32i1 legalization patch https://reviews.llvm.org/D42031.


https://reviews.llvm.org/D42407

Files:
  lib/Target/X86/X86ISelLowering.cpp
  lib/Target/X86/X86InstrAVX512.td


Index: lib/Target/X86/X86InstrAVX512.td
===================================================================
--- lib/Target/X86/X86InstrAVX512.td
+++ lib/Target/X86/X86InstrAVX512.td
@@ -8740,7 +8740,7 @@
 multiclass cvt_by_vec_width<bits<8> opc, X86VectorVTInfo Vec, string OpcodeStr > {
 def rr : AVX512XS8I<opc, MRMSrcReg, (outs Vec.RC:$dst), (ins Vec.KRC:$src),
                   !strconcat(OpcodeStr##Vec.Suffix, "\t{$src, $dst|$dst, $src}"),
-                  [(set Vec.RC:$dst, (Vec.VT (X86vsext Vec.KRC:$src)))],
+                  [(set Vec.RC:$dst, (Vec.VT (sext Vec.KRC:$src)))],
                   IIC_SSE_MOV_S_RR>, EVEX, Sched<[WriteMove]>;
 }
 
@@ -8806,6 +8806,16 @@
 defm VPMOVQ2M : avx512_convert_vector_to_mask<0x39, "vpmovq2m",
                                               avx512vl_i64_info, HasDQI>, VEX_W;
 
+// Patterns for handling sext from a mask register to v16i8/v16i16 when DQI
+// is available, but BWI is not. We can't handle this in lowering because
+// a target independent DAG combine likes to combine sext and trunc.
+let Predicates = [HasDQI, NoBWI] in {
+  def : Pat<(v16i8 (sext (v16i1 VK16:$src))),
+            (VPMOVDBZrr (v16i32 (VPMOVM2DZrr VK16:$src)))>;
+  def : Pat<(v16i16 (sext (v16i1 VK16:$src))),
+            (VPMOVDWZrr (v16i32 (VPMOVM2DZrr VK16:$src)))>;
+}
+
 //===----------------------------------------------------------------------===//
 // AVX-512 - COMPRESS and EXPAND
 //
Index: lib/Target/X86/X86ISelLowering.cpp
===================================================================
--- lib/Target/X86/X86ISelLowering.cpp
+++ lib/Target/X86/X86ISelLowering.cpp
@@ -18669,7 +18669,7 @@
   MVT WideEltVT = WideVT.getVectorElementType();
   if ((Subtarget.hasDQI() && WideEltVT.getSizeInBits() >= 32) ||
       (Subtarget.hasBWI() && WideEltVT.getSizeInBits() <= 16)) {
-    V = getExtendInVec(X86ISD::VSEXT, dl, WideVT, In, DAG);
+    V = DAG.getNode(ISD::SIGN_EXTEND, dl, WideVT, In);
   } else {
     SDValue NegOne = getOnesVector(WideVT, DAG, dl);
     SDValue Zero = getZeroVector(WideVT, Subtarget, DAG, dl);
@@ -25776,7 +25776,15 @@
   return false;
 }
 
-bool X86TargetLowering::isVectorLoadExtDesirable(SDValue) const { return true; }
+bool X86TargetLowering::isVectorLoadExtDesirable(SDValue ExtVal) const {
+  EVT SrcVT = ExtVal.getOperand(0).getValueType();
+
+  // There is no extending load for vXi1.
+  if (SrcVT.getScalarType() == MVT::i1)
+    return false;
+
+  return true;
+}
 
 bool
 X86TargetLowering::isFMAFasterThanFMulAndFAdd(EVT VT) const {


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