[SLP]Update TrackedToOrig mappings after reduction vectorization

Need to update mappings in TrackedToOrig to correctly provide mapping
between updated reduced value after vectorization and its original
value, otherwise the compiler might miss this update and it may cause
compiler crash later, when it tries to find the original instruction
mapping for the updated value.

Fixes #109376

Author: alexey-bataev

llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp

@@ -18668,6 +18668,14 @@ class HorizontalReduction {
         // Vectorize a tree.
         Value *VectorizedRoot =
             V.vectorizeTree(LocalExternallyUsedValues, InsertPt);
+        // Update TrackedToOrig mapping, since the tracked values might be
+        // updated.
+        for (Value *RdxVal : Candidates) {
+          Value *OrigVal = TrackedToOrig.at(RdxVal);
+          Value *TransformedRdxVal = TrackedVals.at(OrigVal);
+          if (TransformedRdxVal != RdxVal)
+            TrackedToOrig.try_emplace(TransformedRdxVal, OrigVal);
+        }
 
         Builder.SetInsertPoint(InsertPt);
 

llvm/test/Transforms/SLPVectorizer/X86/reduced-value-vectorized-later.ll

@@ -0,0 +1,41 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -S -passes=slp-vectorizer -mtriple=x86_64-unknown-linux-gnu < %s | FileCheck %s
+
+define i16 @test() {
+; CHECK-LABEL: define i16 @test() {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    [[TMP0:%.*]] = call i16 @llvm.vector.reduce.or.v8i16(<8 x i16> zeroinitializer)
+; CHECK-NEXT:    [[TMP1:%.*]] = call i16 @llvm.vector.reduce.or.v4i16(<4 x i16> zeroinitializer)
+; CHECK-NEXT:    [[OP_RDX:%.*]] = or i16 [[TMP0]], [[TMP1]]
+; CHECK-NEXT:    [[OP_RDX1:%.*]] = or i16 [[OP_RDX]], 0
+; CHECK-NEXT:    ret i16 [[OP_RDX1]]
+;
+entry:
+  %subi = add i16 0, 0
+  %sub40.i = add i16 %subi, 0
+  %sub41.i = add i16 %subi, 0
+  %sub42.i = add i16 %subi, 0
+  %sub43.i = add i16 %subi, 0
+  %sub44.i = add i16 %subi, 0
+  %sub45.i = add i16 %subi, 0
+  %sub46.i = add i16 0, 0
+  %sub47.i = add i16 0, 0
+  %sub48.i = add i16 0, 0
+  %sub49.i = add i16 0, 0
+  %or40.i = or i16 %sub40.i, %sub41.i
+  %or41.i = or i16 %or40.i, %sub42.i
+  %or42.i = or i16 %or41.i, %sub43.i
+  %or43.i = or i16 %or42.i, %sub44.i
+  %or44.i = or i16 %or43.i, %sub45.i
+  %or45.i = or i16 %or44.i, %sub46.i
+  %or46.i = or i16 %or45.i, %sub47.i
+  %or47.i = or i16 %or46.i, %sub48.i
+  %or48.i = or i16 %or47.i, %sub49.i
+  %or50.i = or i16 %or48.i, %subi
+  %subii = add i16 0, 0
+  %subi16.i = add i16 %subii, 0
+  %subi17.i = add i16 %subii, 0
+  %0 = or i16 %subi16.i, %subi17.i
+  %1 = or i16 %0, %or50.i
+  ret i16 %1
+}