Optimize trivial branches in CodeGenPrepare, which often get created from the

lowering of objectsize intrinsics. Unfortunately, a number of tests were relying
on llc not optimizing trivial branches, so I had to add an option to allow them
to continue to test what they originally tested.

This fixes <rdar://problem/8785296> and <rdar://problem/9112893>.

llvm-svn: 127459

1 files changed, 14 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Scalar/CodeGenPrepare.cpp b/llvm/lib/Transforms/Scalar/CodeGenPrepare.cpp
index 887fa9f004b..f0babcccee0 100644
--- a/llvm/lib/Transforms/Scalar/CodeGenPrepare.cpp
+++ b/llvm/lib/Transforms/Scalar/CodeGenPrepare.cpp
@@ -58,6 +58,10 @@ STATISTIC(NumMemoryInsts, "Number of memory instructions whose address "
 STATISTIC(NumExtsMoved, "Number of [s|z]ext instructions combined with loads");
 STATISTIC(NumExtUses, "Number of uses of [s|z]ext instructions optimized");
 
+static cl::opt<bool> DisableBranchOpts(
+  "disable-cgp-branch-opts", cl::Hidden, cl::init(false),
+  cl::desc("Disable branch optimizations in CodeGenPrepare"));
+
 namespace {
   class CodeGenPrepare : public FunctionPass {
     /// TLI - Keep a pointer of a TargetLowering to consult for determining
@@ -130,6 +134,16 @@ bool CodeGenPrepare::runOnFunction(Function &F) {
 
   SunkAddrs.clear();
 
+  if (!DisableBranchOpts) {
+    MadeChange = false;
+    for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
+      MadeChange |= ConstantFoldTerminator(BB);
+
+    if (MadeChange && DT)
+      DT->DT->recalculate(F);
+    EverMadeChange |= MadeChange;
+  }
+
   return EverMadeChange;
 }