[llvm-branch-commits] [llvm] [CodeGen] Limit number of analyzed predecessors (PR #142584)

[Alexis Engelke via llvm-branch-commits]

https://github.com/aengelke updated https://github.com/llvm/llvm-project/pull/142584

>From 4cbc231699c11444cff73ff28b88dc0f3835c752 Mon Sep 17 00:00:00 2001
From: Alexis Engelke <engelke at in.tum.de>
Date: Wed, 4 Jun 2025 09:21:02 +0000
Subject: [PATCH] Move one check to beginning of function

Created using spr 1.3.5-bogner
---
 llvm/lib/CodeGen/MachineBlockPlacement.cpp | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/llvm/lib/CodeGen/MachineBlockPlacement.cpp b/llvm/lib/CodeGen/MachineBlockPlacement.cpp
index e96f3f8193b09..2dbabfe345d5e 100644
--- a/llvm/lib/CodeGen/MachineBlockPlacement.cpp
+++ b/llvm/lib/CodeGen/MachineBlockPlacement.cpp
@@ -1483,6 +1483,11 @@ bool MachineBlockPlacement::hasBetterLayoutPredecessor(
   if (SuccChain.UnscheduledPredecessors == 0)
     return false;
 
+  // Compile-time optimization: runtime is quadratic in the number of
+  // predecessors. For such uncommon cases, exit early.
+  if (Succ->pred_size() > PredecessorLimit)
+    return false;
+
   // There are two basic scenarios here:
   // -------------------------------------
   // Case 1: triangular shape CFG (if-then):
@@ -1603,11 +1608,6 @@ bool MachineBlockPlacement::hasBetterLayoutPredecessor(
   BlockFrequency CandidateEdgeFreq = MBFI->getBlockFreq(BB) * RealSuccProb;
   bool BadCFGConflict = false;
 
-  // Compile-time optimization: runtime is quadratic in the number of
-  // predecessors. For such uncommon cases, exit early.
-  if (Succ->pred_size() > PredecessorLimit)
-    return false;
-
   for (MachineBasicBlock *Pred : Succ->predecessors()) {
     BlockChain *PredChain = BlockToChain[Pred];
     if (Pred == Succ || PredChain == &SuccChain ||