From: Eli Friedman <eli.friedman@gmail.com>
Date: Tue, 19 Apr 2011 17:01:08 +0000 (+0000)
Subject: SelectBasicBlock is rather slow even when it doesn't do anything; skip the
X-Git-Url: http://plrg.eecs.uci.edu/git/?a=commitdiff_plain;h=37d38bfbbf2b8db2c75b2edbd8cd30c51746fd5d;p=oota-llvm.git

SelectBasicBlock is rather slow even when it doesn't do anything; skip the
unnecessary work where possible.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@129763 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
index 8e599aef7f3..af3188895ed 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
@@ -1017,11 +1017,13 @@ void SelectionDAGISel::SelectAllBasicBlocks(const Function &Fn) {
     else
       ++NumFastIselBlocks;
 
-    // Run SelectionDAG instruction selection on the remainder of the block
-    // not handled by FastISel. If FastISel is not run, this is the entire
-    // block.
-    bool HadTailCall;
-    SelectBasicBlock(Begin, BI, HadTailCall);
+    if (Begin != BI) {
+      // Run SelectionDAG instruction selection on the remainder of the block
+      // not handled by FastISel. If FastISel is not run, this is the entire
+      // block.
+      bool HadTailCall;
+      SelectBasicBlock(Begin, BI, HadTailCall);
+    }
 
     FinishBasicBlock();
     FuncInfo->PHINodesToUpdate.clear();