[PATCH] D23939: IfConversion: Fix branch predication bug.

[Kyle Butt via llvm-commits]

iteratee added inline comments.

================
Comment at: lib/CodeGen/IfConversion.cpp:1778
@@ -1782,4 +1777,3 @@
 
-  if (RemoveTrueBranch)
-    BBI1->NonPredSize -= TII->RemoveBranch(*BBI1->BB);
+  BBI1->NonPredSize -= TII->RemoveBranch(*BBI1->BB);
   // Remove duplicated instructions.
----------------
davidxl wrote:
> Is trueBranch always analyzable?
No, but we have previously verified that both blocks have the same branch instructions, so we only need one copy.

================
Comment at: lib/CodeGen/IfConversion.cpp:1807
@@ -1807,1 +1806,3 @@
+    DI2++;
+  }
   while (NumDups2 != 0) {
----------------
davidxl wrote:
> Why  skipping debug value here? Does that affect the NumDups2 adjustment below?
> Does that affect the NumDups2 adjustment below?
No. NumDups2 doesn't count debug values.

Would it be clearer if it read (DI2->isBranch() || DI2->isDebugValue())?

The goal is to skip all the branch instructions, because they have been checked to match MBB1 and don't need to predicated.
This is where the actual crash was occurring. We were attempting to predicate the branch instruction when we didn't need to.


Repository:
  rL LLVM

https://reviews.llvm.org/D23939