[SLP]Fix a crash when trying to convert masked gather nodes to strided.

Need to check if the loads node is masked gather. Only vectorized loads
can be converted to strided.

Author: alexey-bataev

llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp

@@ -7966,6 +7966,10 @@ void BoUpSLP::transformNodes() {
     TreeEntry &E = *TE.get();
     switch (E.getOpcode()) {
     case Instruction::Load: {
+      // No need to reorder masked gather loads, just reorder the scalar
+      // operands.
+      if (E.State != TreeEntry::Vectorize)
+        break;
       Type *ScalarTy = E.getMainOp()->getType();
       auto *VecTy = FixedVectorType::get(ScalarTy, E.Scalars.size());
       Align CommonAlignment = computeCommonAlignment<LoadInst>(E.Scalars);

llvm/test/Transforms/SLPVectorizer/RISCV/scatter-vectorize-reversed.ll

@@ -0,0 +1,30 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 4
+; RUN: opt -S --passes=slp-vectorizer -mtriple=riscv64-unknown-linux-gnu -mattr=+v -slp-threshold=-11 < %s | FileCheck %s
+
+define <4 x i32> @test(<2 x i64> %v, ptr %p) {
+; CHECK-LABEL: define <4 x i32> @test(
+; CHECK-SAME: <2 x i64> [[V:%.*]], ptr [[P:%.*]]) #[[ATTR0:[0-9]+]] {
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[TMP0:%.*]] = insertelement <2 x ptr> poison, ptr [[P]], i32 0
+; CHECK-NEXT:    [[TMP1:%.*]] = shufflevector <2 x ptr> [[TMP0]], <2 x ptr> poison, <2 x i32> zeroinitializer
+; CHECK-NEXT:    [[TMP2:%.*]] = getelementptr i16, <2 x ptr> [[TMP1]], <2 x i64> [[V]]
+; CHECK-NEXT:    [[TMP3:%.*]] = call <2 x i16> @llvm.masked.gather.v2i16.v2p0(<2 x ptr> [[TMP2]], i32 2, <2 x i1> <i1 true, i1 true>, <2 x i16> poison)
+; CHECK-NEXT:    [[TMP4:%.*]] = shufflevector <2 x i16> [[TMP3]], <2 x i16> poison, <2 x i32> <i32 1, i32 0>
+; CHECK-NEXT:    [[TMP7:%.*]] = zext <2 x i16> [[TMP4]] to <2 x i32>
+; CHECK-NEXT:    [[TMP6:%.*]] = shufflevector <2 x i32> [[TMP7]], <2 x i32> poison, <4 x i32> <i32 0, i32 1, i32 poison, i32 poison>
+; CHECK-NEXT:    [[TMP5:%.*]] = shufflevector <4 x i32> zeroinitializer, <4 x i32> [[TMP6]], <4 x i32> <i32 4, i32 5, i32 2, i32 3>
+; CHECK-NEXT:    ret <4 x i32> [[TMP5]]
+;
+entry:
+  %0 = extractelement <2 x i64> %v, i32 1
+  %arrayidx127.2 = getelementptr i16, ptr %p, i64 %0
+  %1 = load i16, ptr %arrayidx127.2, align 2
+  %conv128.2 = zext i16 %1 to i32
+  %2 = extractelement <2 x i64> %v, i32 0
+  %arrayidx127.3 = getelementptr i16, ptr %p, i64 %2
+  %3 = load i16, ptr %arrayidx127.3, align 2
+  %conv128.3 = zext i16 %3 to i32
+  %4 = insertelement <4 x i32> zeroinitializer, i32 %conv128.2, i32 0
+  %5 = insertelement <4 x i32> %4, i32 %conv128.3, i32 1
+  ret <4 x i32> %5
+}