[PATCH] D127974: [SLP]Use original vector if need to shuffle truncated root.

[Alexey Bataev via Phabricator via llvm-commits]

ABataev created this revision.
ABataev added reviewers: RKSimon, scui.
Herald added subscribers: vporpo, hiraditya.
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If the root scalar is mapped to to the smallest bit width, the vector is
truncated and the types between original buildvector and extracted value
mismatched. For extract, we emit sext/zext instructions, for shuffles we
can reuse oringal vector instead of the truncated one.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D127974

Files:
  llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
  llvm/test/Transforms/SLPVectorizer/X86/root-trunc-extract-reuse.ll


Index: llvm/test/Transforms/SLPVectorizer/X86/root-trunc-extract-reuse.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/SLPVectorizer/X86/root-trunc-extract-reuse.ll
@@ -0,0 +1,46 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -slp-vectorizer -S -slp-threshold=-100 -mtriple=x86_64 < %s | FileCheck %s
+
+define i1 @test() {
+; CHECK-LABEL: @test(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br i1 false, label [[THEN:%.*]], label [[ELSE:%.*]]
+; CHECK:       then:
+; CHECK-NEXT:    br label [[ELSE]]
+; CHECK:       else:
+; CHECK-NEXT:    [[TMP0:%.*]] = phi <2 x i32> [ zeroinitializer, [[THEN]] ], [ zeroinitializer, [[ENTRY:%.*]] ]
+; CHECK-NEXT:    [[TMP1:%.*]] = trunc <2 x i32> [[TMP0]] to <2 x i8>
+; CHECK-NEXT:    [[TMP2:%.*]] = extractelement <2 x i8> [[TMP1]], i32 0
+; CHECK-NEXT:    [[TMP3:%.*]] = zext i8 [[TMP2]] to i32
+; CHECK-NEXT:    [[BF_CAST162:%.*]] = and i32 [[TMP3]], 0
+; CHECK-NEXT:    [[TMP4:%.*]] = shufflevector <2 x i32> zeroinitializer, <2 x i32> [[TMP0]], <2 x i32> <i32 3, i32 1>
+; CHECK-NEXT:    [[T13:%.*]] = and <2 x i32> [[TMP4]], zeroinitializer
+; CHECK-NEXT:    br label [[ELSE1:%.*]]
+; CHECK:       else1:
+; CHECK-NEXT:    [[T20:%.*]] = extractelement <2 x i32> [[T13]], i64 0
+; CHECK-NEXT:    [[TMP5:%.*]] = insertelement <2 x i32> poison, i32 [[BF_CAST162]], i32 0
+; CHECK-NEXT:    [[TMP6:%.*]] = insertelement <2 x i32> [[TMP5]], i32 [[T20]], i32 1
+; CHECK-NEXT:    [[TMP7:%.*]] = icmp ugt <2 x i32> [[TMP6]], zeroinitializer
+; CHECK-NEXT:    [[TMP8:%.*]] = extractelement <2 x i1> [[TMP7]], i32 1
+; CHECK-NEXT:    ret i1 [[TMP8]]
+;
+entry:
+  br i1 false, label %then, label %else
+
+then:
+  br label %else
+
+else:
+  %bf.load.off43 = phi i32 [ 0, %then ], [ 0, %entry ]
+  %bf.load.off44 = phi i32 [ 0, %then ], [ 0, %entry ]
+  %bf.cast162 = and i32 %bf.load.off43, 0
+  %t12 = insertelement <2 x i32> zeroinitializer, i32 %bf.load.off44, i64 0
+  %t13 = and <2 x i32> %t12, zeroinitializer
+  br label %else1
+
+else1:
+  %cmp40 = icmp ugt i32 %bf.cast162, 0
+  %t20 = extractelement <2 x i32> %t13, i64 0
+  %cmp50 = icmp ugt i32 %t20, 0
+  ret i1 %cmp50
+}
Index: llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
===================================================================
--- llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -8472,6 +8472,10 @@
         if (auto *FTy = dyn_cast<FixedVectorType>(User->getType())) {
           Optional<unsigned> InsertIdx = getInsertIndex(VU);
           if (InsertIdx) {
+            // Need to use original vector, if the root is truncated.
+            if (MinBWs.count(Scalar) &&
+                VectorizableTree[0]->VectorizedValue == Vec)
+              Vec = VectorRoot;
             auto *It =
                 find_if(ShuffledInserts, [VU](const ShuffledInsertData &Data) {
                   // Checks if 2 insertelements are from the same buildvector.


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