From bcd09b3a7f21b60945c84bde1343eabfb2ab2709 Mon Sep 17 00:00:00 2001
From: Eli Friedman <eli.friedman@gmail.com>
Date: Tue, 19 Apr 2011 17:01:08 +0000
Subject: SelectBasicBlock is rather slow even when it doesn't do anything;
 skip the unnecessary work where possible.

llvm-svn: 129763
---
 llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

(limited to 'llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp')

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
index 8e599aef7f3..af3188895ed 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
+++ b/llvm/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();
-- 
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