[llvm] r247784 - [X86] Fix emitEpilogue() to make less assumptions about pops

[Michael Kuperstein via llvm-commits]

Author: mkuper
Date: Wed Sep 16 06:18:25 2015
New Revision: 247784

URL: http://llvm.org/viewvc/llvm-project?rev=247784&view=rev
Log:
[X86] Fix emitEpilogue() to make less assumptions about pops

This is the mirror image of r242395.
When X86FrameLowering::emitEpilogue() looks for where to insert the %esp addition that
deallocates stack space used for local allocations, it assumes that any sequence of pop
instructions from function exit backwards consists purely of restoring callee-save registers.

This may be false, since from some point backward, the pops may be clean-up of stack space
allocated for arguments to a call.

Patch by: amjad.aboud at intel.com
Differential Revision: http://reviews.llvm.org/D12688

Modified:
    llvm/trunk/include/llvm/CodeGen/MachineInstr.h
    llvm/trunk/lib/CodeGen/MachineInstr.cpp
    llvm/trunk/lib/Target/X86/X86FrameLowering.cpp

Modified: llvm/trunk/include/llvm/CodeGen/MachineInstr.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/CodeGen/MachineInstr.h?rev=247784&r1=247783&r2=247784&view=diff
==============================================================================
--- llvm/trunk/include/llvm/CodeGen/MachineInstr.h (original)
+++ llvm/trunk/include/llvm/CodeGen/MachineInstr.h Wed Sep 16 06:18:25 2015
@@ -64,8 +64,10 @@ public:
     NoFlags      = 0,
     FrameSetup   = 1 << 0,              // Instruction is used as a part of
                                         // function frame setup code.
-    BundledPred  = 1 << 1,              // Instruction has bundled predecessors.
-    BundledSucc  = 1 << 2               // Instruction has bundled successors.
+    FrameDestroy = 1 << 1,              // Instruction is used as a part of
+                                        // function frame destruction code.
+    BundledPred  = 1 << 2,              // Instruction has bundled predecessors.
+    BundledSucc  = 1 << 3               // Instruction has bundled successors.
   };
 private:
   const MCInstrDesc *MCID;              // Instruction descriptor.

Modified: llvm/trunk/lib/CodeGen/MachineInstr.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/MachineInstr.cpp?rev=247784&r1=247783&r2=247784&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/MachineInstr.cpp (original)
+++ llvm/trunk/lib/CodeGen/MachineInstr.cpp Wed Sep 16 06:18:25 2015
@@ -1735,13 +1735,16 @@ void MachineInstr::print(raw_ostream &OS
   }
 
   bool HaveSemi = false;
-  const unsigned PrintableFlags = FrameSetup;
+  const unsigned PrintableFlags = FrameSetup | FrameDestroy;
   if (Flags & PrintableFlags) {
     if (!HaveSemi) OS << ";"; HaveSemi = true;
     OS << " flags: ";
 
     if (Flags & FrameSetup)
       OS << "FrameSetup";
+
+    if (Flags & FrameDestroy)
+      OS << "FrameDestroy";
   }
 
   if (!memoperands_empty()) {

Modified: llvm/trunk/lib/Target/X86/X86FrameLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86FrameLowering.cpp?rev=247784&r1=247783&r2=247784&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86FrameLowering.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86FrameLowering.cpp Wed Sep 16 06:18:25 2015
@@ -286,6 +286,8 @@ void X86FrameLowering::emitSPUpdate(Mach
           .addReg(Reg, getDefRegState(!isSub) | getUndefRegState(isSub));
         if (isSub)
           MI->setFlag(MachineInstr::FrameSetup);
+        else
+          MI->setFlag(MachineInstr::FrameDestroy);
         Offset -= ThisVal;
         continue;
       }
@@ -295,6 +297,8 @@ void X86FrameLowering::emitSPUpdate(Mach
         MBB, MBBI, DL, isSub ? -ThisVal : ThisVal, InEpilogue);
     if (isSub)
       MI.setMIFlag(MachineInstr::FrameSetup);
+    else
+      MI.setMIFlag(MachineInstr::FrameDestroy);
 
     Offset -= ThisVal;
   }
@@ -1075,7 +1079,7 @@ void X86FrameLowering::emitEpilogue(Mach
 
     // Pop EBP.
     BuildMI(MBB, MBBI, DL, TII.get(Is64Bit ? X86::POP64r : X86::POP32r),
-            MachineFramePtr);
+            MachineFramePtr).setMIFlag(MachineInstr::FrameDestroy);
   } else if (hasFP(MF)) {
     // Calculate required stack adjustment.
     uint64_t FrameSize = StackSize - SlotSize;
@@ -1088,7 +1092,8 @@ void X86FrameLowering::emitEpilogue(Mach
 
     // Pop EBP.
     BuildMI(MBB, MBBI, DL,
-            TII.get(Is64Bit ? X86::POP64r : X86::POP32r), MachineFramePtr);
+            TII.get(Is64Bit ? X86::POP64r : X86::POP32r), MachineFramePtr)
+        .setMIFlag(MachineInstr::FrameDestroy);
   } else {
     NumBytes = StackSize - CSSize;
   }
@@ -1099,8 +1104,9 @@ void X86FrameLowering::emitEpilogue(Mach
     MachineBasicBlock::iterator PI = std::prev(MBBI);
     unsigned Opc = PI->getOpcode();
 
-    if (Opc != X86::POP32r && Opc != X86::POP64r && Opc != X86::DBG_VALUE &&
-        !PI->isTerminator())
+    if ((Opc != X86::POP32r || !PI->getFlag(MachineInstr::FrameDestroy)) &&
+        (Opc != X86::POP64r || !PI->getFlag(MachineInstr::FrameDestroy)) &&
+        Opc != X86::DBG_VALUE && !PI->isTerminator())
       break;
 
     --MBBI;
@@ -1463,7 +1469,8 @@ bool X86FrameLowering::restoreCalleeSave
         !X86::GR32RegClass.contains(Reg))
       continue;
 
-    BuildMI(MBB, MI, DL, TII.get(Opc), Reg);
+    BuildMI(MBB, MI, DL, TII.get(Opc), Reg)
+        .setMIFlag(MachineInstr::FrameDestroy);
   }
   return true;
 }