[PATCH] D57186: [SelectionDAG][X86] Don't use SEXTLOAD for promoting masked loads in the type legalizer

[Craig Topper via Phabricator via llvm-commits]

craig.topper created this revision.
craig.topper added reviewers: RKSimon, spatel.

I'm not sure why we were using SEXTLOAD. EXTLOAD seems more appropriate since we don't care about the upper bits.

This patch changes this and then modifies the X86 post legalization combine to emit a extending shuffle instead of a sign_extend_vector_inreg. Could maybe use an any_extend_vector_inreg, but I just did what we already do in LowerLoad. I think we can actually get rid of this code entirely if we switch to -x86-experimental-vector-widening-legalization.

On AVX512 targets I think we might be able to use a masked vpmovzx and not have to expand this at all.


https://reviews.llvm.org/D57186

Files:
  lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp
  lib/Target/X86/X86ISelLowering.cpp
  test/CodeGen/X86/masked_load.ll


Index: test/CodeGen/X86/masked_load.ll
===================================================================
--- test/CodeGen/X86/masked_load.ll
+++ test/CodeGen/X86/masked_load.ll
@@ -1388,7 +1388,7 @@
 ; AVX1-NEXT:    vmaskmovps (%rdi), %xmm0, %xmm2
 ; AVX1-NEXT:    vpermilps {{.*#+}} xmm1 = xmm1[0,2,2,3]
 ; AVX1-NEXT:    vblendvps %xmm0, %xmm2, %xmm1, %xmm0
-; AVX1-NEXT:    vpmovsxdq %xmm0, %xmm0
+; AVX1-NEXT:    vpmovzxdq {{.*#+}} xmm0 = xmm0[0],zero,xmm0[1],zero
 ; AVX1-NEXT:    retq
 ;
 ; AVX2-LABEL: load_v2i32_v2i32:
@@ -1400,7 +1400,7 @@
 ; AVX2-NEXT:    vpmaskmovd (%rdi), %xmm0, %xmm2
 ; AVX2-NEXT:    vpermilps {{.*#+}} xmm1 = xmm1[0,2,2,3]
 ; AVX2-NEXT:    vblendvps %xmm0, %xmm2, %xmm1, %xmm0
-; AVX2-NEXT:    vpmovsxdq %xmm0, %xmm0
+; AVX2-NEXT:    vpmovzxdq {{.*#+}} xmm0 = xmm0[0],zero,xmm0[1],zero
 ; AVX2-NEXT:    retq
 ;
 ; AVX512F-LABEL: load_v2i32_v2i32:
@@ -1412,7 +1412,7 @@
 ; AVX512F-NEXT:    kshiftlw $14, %k0, %k0
 ; AVX512F-NEXT:    kshiftrw $14, %k0, %k1
 ; AVX512F-NEXT:    vmovdqu32 (%rdi), %zmm0 {%k1}
-; AVX512F-NEXT:    vpmovsxdq %xmm0, %xmm0
+; AVX512F-NEXT:    vpmovzxdq {{.*#+}} xmm0 = xmm0[0],zero,xmm0[1],zero
 ; AVX512F-NEXT:    vzeroupper
 ; AVX512F-NEXT:    retq
 ;
@@ -1423,7 +1423,7 @@
 ; AVX512VLBW-NEXT:    vptestnmq %xmm0, %xmm0, %k1
 ; AVX512VLBW-NEXT:    vpshufd {{.*#+}} xmm0 = xmm1[0,2,2,3]
 ; AVX512VLBW-NEXT:    vmovdqu32 (%rdi), %xmm0 {%k1}
-; AVX512VLBW-NEXT:    vpmovsxdq %xmm0, %xmm0
+; AVX512VLBW-NEXT:    vpmovzxdq {{.*#+}} xmm0 = xmm0[0],zero,xmm0[1],zero
 ; AVX512VLBW-NEXT:    retq
   %mask = icmp eq <2 x i32> %trigger, zeroinitializer
   %res = call <2 x i32> @llvm.masked.load.v2i32.p0v2i32(<2 x i32>* %addr, i32 4, <2 x i1>%mask, <2 x i32>%dst)
Index: lib/Target/X86/X86ISelLowering.cpp
===================================================================
--- lib/Target/X86/X86ISelLowering.cpp
+++ lib/Target/X86/X86ISelLowering.cpp
@@ -37519,7 +37519,7 @@
         return Blend;
   }
 
-  if (Mld->getExtensionType() != ISD::SEXTLOAD)
+  if (Mld->getExtensionType() != ISD::EXTLOAD)
     return SDValue();
 
   // Resolve extending loads.
@@ -37589,8 +37589,20 @@
                                      Mld->getBasePtr(), NewMask, WidePassThru,
                                      Mld->getMemoryVT(), Mld->getMemOperand(),
                                      ISD::NON_EXTLOAD);
-  SDValue NewVec = getExtendInVec(/*Signed*/true, dl, VT, WideLd, DAG);
-  return DCI.CombineTo(N, NewVec, WideLd.getValue(1), true);
+
+  SDValue SlicedVec = DAG.getBitcast(WideVecVT, WideLd);
+  SmallVector<int, 16> ShuffleVec(NumElems * SizeRatio, -1);
+  for (unsigned i = 0; i != NumElems; ++i)
+    ShuffleVec[i * SizeRatio] = i;
+
+  // Can't shuffle using an illegal type.
+  assert(DAG.getTargetLoweringInfo().isTypeLegal(WideVecVT) &&
+         "WideVecVT should be legal");
+  SlicedVec = DAG.getVectorShuffle(WideVecVT, dl, SlicedVec,
+                                   DAG.getUNDEF(WideVecVT), ShuffleVec);
+  SlicedVec = DAG.getBitcast(VT, SlicedVec);
+
+  return DCI.CombineTo(N, SlicedVec, WideLd.getValue(1), true);
 }
 
 /// If exactly one element of the mask is set for a non-truncating masked store,
Index: lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp
===================================================================
--- lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp
+++ lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp
@@ -554,7 +554,7 @@
   SDLoc dl(N);
   SDValue Res = DAG.getMaskedLoad(NVT, dl, N->getChain(), N->getBasePtr(),
                                   N->getMask(), ExtPassThru, N->getMemoryVT(),
-                                  N->getMemOperand(), ISD::SEXTLOAD);
+                                  N->getMemOperand(), ISD::EXTLOAD);
   // Legalize the chain result - switch anything that used the old chain to
   // use the new one.
   ReplaceValueWith(SDValue(N, 1), Res.getValue(1));


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