[IPO] Temporarily rollback r307215.

[GlobalOpt] Remove unreachable blocks before optimizing a function.
While the change is presumably correct, it exposes a latent bug
in DI which breaks on of the CFI checks. I'll analyze it further
and try to understand what's going on.

llvm-svn: 307729

1 files changed, 0 insertions, 18 deletions

diff --git a/llvm/lib/Transforms/IPO/GlobalOpt.cpp b/llvm/lib/Transforms/IPO/GlobalOpt.cpp
index 93eab680ca6..3d57acf06e7 100644
--- a/llvm/lib/Transforms/IPO/GlobalOpt.cpp
+++ b/llvm/lib/Transforms/IPO/GlobalOpt.cpp
@@ -2026,24 +2026,6 @@ OptimizeFunctions(Module &M, TargetLibraryInfo *TLI,
       continue;
     }
 
-    // LLVM's definition of dominance allows instructions that are cyclic
-    // in unreachable blocks, e.g.:
-    // %pat = select i1 %condition, @global, i16* %pat
-    // because any instruction dominates an instruction in a block that's
-    // not reachable from entry.
-    // So, remove unreachable blocks from the function, because a) there's
-    // no point in analyzing them and b) GlobalOpt should otherwise grow
-    // some more complicated logic to break these cycles.
-    // Removing unreachable blocks might invalidate the dominator so we
-    // recalculate it.
-    if (!F->isDeclaration()) {
-      if (removeUnreachableBlocks(*F)) {
-        auto &DT = LookupDomTree(*F);
-        DT.recalculate(*F);
-        Changed = true;
-      }
-    }
-
     Changed |= processGlobal(*F, TLI, LookupDomTree);
 
     if (!F->hasLocalLinkage())