Avoid extra vreg copies for arguments passed in registers. Specifically, this can make MachineCSE more effective in some cases (especially in small functions). PR8361 / part of rdar://problem/8259436 .

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@130928 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 0 insertions, 26 deletions

diff --git a/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp b/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp
index d8a5770d36..a1e8254189 100644
--- a/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp
+++ b/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp
@@ -54,25 +54,6 @@ static bool isUsedOutsideOfDefiningBlock(const Instruction *I) {
   return false;
 }
 
-/// isOnlyUsedInEntryBlock - If the specified argument is only used in the
-/// entry block, return true.  This includes arguments used by switches, since
-/// the switch may expand into multiple basic blocks.
-static bool isOnlyUsedInEntryBlock(const Argument *A, bool EnableFastISel) {
-  // With FastISel active, we may be splitting blocks, so force creation
-  // of virtual registers for all non-dead arguments.
-  if (EnableFastISel)
-    return A->use_empty();
-
-  const BasicBlock *Entry = A->getParent()->begin();
-  for (Value::const_use_iterator UI = A->use_begin(), E = A->use_end();
-       UI != E; ++UI) {
-    const User *U = *UI;
-    if (cast<Instruction>(U)->getParent() != Entry || isa<SwitchInst>(U))
-      return false;  // Use not in entry block.
-  }
-  return true;
-}
-
 FunctionLoweringInfo::FunctionLoweringInfo(const TargetLowering &tli)
   : TLI(tli) {
 }
@@ -89,13 +70,6 @@ void FunctionLoweringInfo::set(const Function &fn, MachineFunction &mf) {
   CanLowerReturn = TLI.CanLowerReturn(Fn->getCallingConv(), Fn->isVarArg(),
                                       Outs, Fn->getContext());
 
-  // Create a vreg for each argument register that is not dead and is used
-  // outside of the entry block for the function.
-  for (Function::const_arg_iterator AI = Fn->arg_begin(), E = Fn->arg_end();
-       AI != E; ++AI)
-    if (!isOnlyUsedInEntryBlock(AI, EnableFastISel))
-      InitializeRegForValue(AI);
-
   // Initialize the mapping of values to registers.  This is only set up for
   // instruction values that are used outside of the block that defines
   // them.