[PATCH] D120651: [SCEV] Only verify BECounts for reachable loops (PR50523)

[Nikita Popov via Phabricator via llvm-commits]

This revision was landed with ongoing or failed builds.
This revision was automatically updated to reflect the committed changes.
Closed by commit rGaeab6167b0a1: [SCEV] Only verify BECounts for reachable loops (PR50523) (authored by nikic).

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D120651/new/

https://reviews.llvm.org/D120651

Files:
  llvm/lib/Analysis/ScalarEvolution.cpp
  llvm/test/Transforms/IndVarSimplify/X86/pr35406.ll


Index: llvm/test/Transforms/IndVarSimplify/X86/pr35406.ll
===================================================================
--- llvm/test/Transforms/IndVarSimplify/X86/pr35406.ll
+++ llvm/test/Transforms/IndVarSimplify/X86/pr35406.ll
@@ -1,5 +1,5 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
-; RUN: opt -S -indvars %s | FileCheck %s
+; RUN: opt -S -passes='loop(indvars),verify<scalar-evolution>' %s | FileCheck %s
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128-ni:1"
 target triple = "x86_64-unknown-linux-gnu"
 
Index: llvm/lib/Analysis/ScalarEvolution.cpp
===================================================================
--- llvm/lib/Analysis/ScalarEvolution.cpp
+++ llvm/lib/Analysis/ScalarEvolution.cpp
@@ -13410,6 +13410,25 @@
   SCEVTraversal<FindUsedLoops>(F).visitAll(S);
 }
 
+static void getReachableBlocks(SmallPtrSetImpl<BasicBlock *> &Reachable,
+                               Function &F) {
+  SmallVector<BasicBlock *> Worklist;
+  Worklist.push_back(&F.getEntryBlock());
+  while (!Worklist.empty()) {
+    BasicBlock *BB = Worklist.pop_back_val();
+    if (!Reachable.insert(BB).second)
+      continue;
+
+    const APInt *Cond;
+    BasicBlock *TrueBB, *FalseBB;
+    if (match(BB->getTerminator(),
+              m_Br(m_APInt(Cond), m_BasicBlock(TrueBB), m_BasicBlock(FalseBB))))
+      Worklist.push_back(Cond->isOne() ? TrueBB : FalseBB);
+    else
+      append_range(Worklist, successors(BB));
+  }
+}
+
 void ScalarEvolution::verify() const {
   ScalarEvolution &SE = *const_cast<ScalarEvolution *>(this);
   ScalarEvolution SE2(F, TLI, AC, DT, LI);
@@ -13434,11 +13453,18 @@
   };
 
   SCEVMapper SCM(SE2);
+  SmallPtrSet<BasicBlock *, 16> ReachableBlocks;
+  getReachableBlocks(ReachableBlocks, F);
 
   while (!LoopStack.empty()) {
     auto *L = LoopStack.pop_back_val();
     llvm::append_range(LoopStack, *L);
 
+    // Only verify BECounts in reachable loops. For an unreachable loop,
+    // any BECount is legal.
+    if (!ReachableBlocks.contains(L->getHeader()))
+      continue;
+
     auto *CurBECount = SCM.visit(
         const_cast<ScalarEvolution *>(this)->getBackedgeTakenCount(L));
     auto *NewBECount = SE2.getBackedgeTakenCount(L);


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