ifcvt should ignore cfg where true and false successors are the same.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@73423 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 12 insertions, 1 deletions

diff --git a/lib/CodeGen/IfConversion.cpp b/lib/CodeGen/IfConversion.cpp
index 1d0887f843..4d5c3c2c7d 100644
--- a/lib/CodeGen/IfConversion.cpp
+++ b/lib/CodeGen/IfConversion.cpp
@@ -547,7 +547,11 @@ void IfConverter::ScanInstructions(BBInfo &BBI) {
     // fallthrough.
     if (!BBI.FalseBB)
       BBI.FalseBB = findFalseBlock(BBI.BB, BBI.TrueBB);  
-    assert(BBI.FalseBB && "Expected to find the fallthrough block!");
+    if (!BBI.FalseBB) {
+      // Malformed bcc? True and false blocks are the same?
+      BBI.IsUnpredicable = true;
+      return;
+    }
   }
 
   // Then scan all the instructions.
@@ -663,6 +667,13 @@ IfConverter::BBInfo &IfConverter::AnalyzeBlock(MachineBasicBlock *BB,
     return BBI;
   }
 
+  // Do not ifcvt if true and false fallthrough blocks are the same.
+  if (!BBI.FalseBB) {
+    BBI.IsBeingAnalyzed = false;
+    BBI.IsAnalyzed = true;
+    return BBI;
+  }
+
   BBInfo &TrueBBI  = AnalyzeBlock(BBI.TrueBB, Tokens);
   BBInfo &FalseBBI = AnalyzeBlock(BBI.FalseBB, Tokens);