Oops, I really wanted to commit this part also :)

llvm-svn: 42700

1 files changed, 27 insertions, 2 deletions

diff --git a/llvm/lib/Target/X86/X86RegisterInfo.cpp b/llvm/lib/Target/X86/X86RegisterInfo.cpp
index 25fa3d66e68..e923606021e 100644
--- a/llvm/lib/Target/X86/X86RegisterInfo.cpp
+++ b/llvm/lib/Target/X86/X86RegisterInfo.cpp
@@ -1500,6 +1500,31 @@ void mergeSPUpdatesUp(MachineBasicBlock &MBB, MachineBasicBlock::iterator &MBBI,
   }
 }
 
+// mergeSPUpdatesUp - Merge two stack-manipulating instructions lower iterator.
+static
+void mergeSPUpdatesDown(MachineBasicBlock &MBB,MachineBasicBlock::iterator &MBBI,
+                        unsigned StackPtr, uint64_t *NumBytes = NULL) {
+  if (MBBI != MBB.end()) {
+    MachineBasicBlock::iterator NI = next(MBBI);
+    unsigned Opc = NI->getOpcode();
+    if ((Opc == X86::ADD64ri32 || Opc == X86::ADD64ri8 ||
+         Opc == X86::ADD32ri || Opc == X86::ADD32ri8) &&
+        NI->getOperand(0).getReg() == StackPtr) {
+      if (NumBytes)
+        *NumBytes -= NI->getOperand(2).getImm();
+      MBB.erase(NI);
+      MBBI = NI;
+    } else if ((Opc == X86::SUB64ri32 || Opc == X86::SUB64ri8 ||
+                Opc == X86::SUB32ri || Opc == X86::SUB32ri8) &&
+               NI->getOperand(0).getReg() == StackPtr) {
+      if (NumBytes)
+        *NumBytes += NI->getOperand(2).getImm();
+      MBB.erase(NI);
+      MBBI = NI;
+    }
+  }
+}
+
 void X86RegisterInfo::emitPrologue(MachineFunction &MF) const {
   MachineBasicBlock &MBB = MF.front();   // Prolog goes in entry BB
   MachineFrameInfo *MFI = MF.getFrameInfo();
@@ -1585,9 +1610,9 @@ void X86RegisterInfo::emitPrologue(MachineFunction &MF) const {
         MBB.insert(MBBI, MI);
       }
     } else {
-      // If there is an ADD32ri or SUB32ri of ESP immediately before this
+      // If there is an ADD32ri or SUB32ri of ESP immediately after this
       // instruction, merge the two instructions.
-      mergeSPUpdatesUp(MBB, MBBI, StackPtr, &NumBytes);
+      mergeSPUpdatesDown(MBB, MBBI, StackPtr, &NumBytes);
       
       if (NumBytes)
         emitSPUpdate(MBB, MBBI, StackPtr, -(int64_t)NumBytes, Is64Bit, TII);