[SLP]Fix PR87011: Do not assume that initial ext/trunc nodes can be

represented by bitwidth without analysis.

Need to check that initial ext/trunc nodes can be safely represented
using calculated bitwidth before applying it.

Author: alexey-bataev

llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp

@@ -14450,9 +14450,15 @@ void BoUpSLP::computeMinimumValueSizes() {
         ReductionBitWidth = 0;
     }
 
-    for (unsigned Idx : RootDemotes)
-      ToDemote.append(VectorizableTree[Idx]->Scalars.begin(),
-                      VectorizableTree[Idx]->Scalars.end());
+    for (unsigned Idx : RootDemotes) {
+      Value *V = VectorizableTree[Idx]->Scalars.front();
+      uint32_t OrigBitWidth = DL->getTypeSizeInBits(V->getType());
+      if (OrigBitWidth > MaxBitWidth) {
+      APInt Mask = APInt::getBitsSetFrom(OrigBitWidth, MaxBitWidth);
+      if (MaskedValueIsZero(V, Mask, SimplifyQuery(*DL)))
+        ToDemote.push_back(V);
+      }
+    }
     RootDemotes.clear();
     IsTopRoot = false;
     IsProfitableToDemoteRoot = true;

llvm/test/Transforms/SLPVectorizer/RISCV/init-ext-node-not-truncable.ll

@@ -1,13 +1,13 @@
 ; 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" < %s | FileCheck %s
+; RUN: opt -S --passes=slp-vectorizer -mtriple=riscv64-unknown-linux-gnu -mattr="+v" < %s -slp-threshold=-5 | FileCheck %s
 
 @h = global [16 x i64] zeroinitializer
 
 define void @test() {
 ; CHECK-LABEL: define void @test(
 ; CHECK-SAME: ) #[[ATTR0:[0-9]+]] {
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    store <2 x i64> <i64 1, i64 0>, ptr @h, align 8
+; CHECK-NEXT:    store <2 x i64> <i64 -1, i64 0>, ptr @h, align 8
 ; CHECK-NEXT:    ret void
 ;
 entry: