[X86] Convert esp-relative movs of function arguments to pushes, step 2

This moves the transformation introduced in r223757 into a separate MI pass.
This allows it to cover many more cases (not only cases where there must be a 
reserved call frame), and perform rudimentary call folding. It still doesn't 
have a heuristic, so it is enabled only for optsize/minsize, with stack 
alignment <= 8, where it ought to be a fairly clear win.

Differential Revision: http://reviews.llvm.org/D6789

llvm-svn: 227728

1 files changed, 5 insertions, 0 deletions

diff --git a/llvm/lib/Target/X86/X86InstrInfo.h b/llvm/lib/Target/X86/X86InstrInfo.h
index 5662e86932c..4d15467f0ca 100644
--- a/llvm/lib/Target/X86/X86InstrInfo.h
+++ b/llvm/lib/Target/X86/X86InstrInfo.h
@@ -175,6 +175,11 @@ public:
   ///
   const X86RegisterInfo &getRegisterInfo() const { return RI; }
 
+  /// getSPAdjust - This returns the stack pointer adjustment made by
+  /// this instruction. For x86, we need to handle more complex call
+  /// sequences involving PUSHes.
+  int getSPAdjust(const MachineInstr *MI) const override;
+
   /// isCoalescableExtInstr - Return true if the instruction is a "coalescable"
   /// extension instruction. That is, it's like a copy where it's legal for the
   /// source to overlap the destination. e.g. X86::MOVSX64rr32. If this returns