Remove the X86 Maximal Stack Alignment Check pass as it is no longer necessary.

This pass was conservative in that it always reserved the FP to enable dynamic
stack realignment, which allowed the RA to use aligned spills for vector
registers.  This happens even when spills were not necessary.  The RA has 
since been improved to use unaligned spills when necessary.

The new behavior is to realign the stack if the frame pointer was already
reserved for some other reason, but don't reserve the frame pointer just
because a function contains vector virtual registers.

Part of rdar://12719844

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@168627 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 0 insertions, 50 deletions

diff --git a/lib/Target/X86/X86.h b/lib/Target/X86/X86.h
index dce5b4d2b0..1e7b98d94f 100644
--- a/lib/Target/X86/X86.h
+++ b/lib/Target/X86/X86.h
@@ -63,12 +63,6 @@ FunctionPass *createX86JITCodeEmitterPass(X86TargetMachine &TM,
 ///
 FunctionPass *createEmitX86CodeToMemory();
 
-/// createX86MaxStackAlignmentHeuristicPass - This function returns a pass
-/// which determines whether the frame pointer register should be
-/// reserved in case dynamic stack alignment is later required.
-///
-FunctionPass *createX86MaxStackAlignmentHeuristicPass();
-
 } // End llvm namespace
 
 #endif
diff --git a/lib/Target/X86/X86RegisterInfo.cpp b/lib/Target/X86/X86RegisterInfo.cpp
index 11f2d7aa70..48f5ae176a 100644
--- a/lib/Target/X86/X86RegisterInfo.cpp
+++ b/lib/Target/X86/X86RegisterInfo.cpp
@@ -789,46 +789,3 @@ unsigned getX86SubSuperRegister(unsigned Reg, MVT::SimpleValueType VT,
   }
 }
 }
-
-namespace {
-  struct MSAH : public MachineFunctionPass {
-    static char ID;
-    MSAH() : MachineFunctionPass(ID) {}
-
-    virtual bool runOnMachineFunction(MachineFunction &MF) {
-      const X86TargetMachine *TM =
-        static_cast<const X86TargetMachine *>(&MF.getTarget());
-      const TargetFrameLowering *TFI = TM->getFrameLowering();
-      MachineRegisterInfo &RI = MF.getRegInfo();
-      X86MachineFunctionInfo *FuncInfo = MF.getInfo<X86MachineFunctionInfo>();
-      unsigned StackAlignment = TFI->getStackAlignment();
-
-      // Be over-conservative: scan over all vreg defs and find whether vector
-      // registers are used. If yes, there is a possibility that vector register
-      // will be spilled and thus require dynamic stack realignment.
-      for (unsigned i = 0, e = RI.getNumVirtRegs(); i != e; ++i) {
-        unsigned Reg = TargetRegisterInfo::index2VirtReg(i);
-        if (RI.getRegClass(Reg)->getAlignment() > StackAlignment) {
-          FuncInfo->setForceFramePointer(true);
-          return true;
-        }
-      }
-      // Nothing to do
-      return false;
-    }
-
-    virtual const char *getPassName() const {
-      return "X86 Maximal Stack Alignment Check";
-    }
-
-    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
-      AU.setPreservesCFG();
-      MachineFunctionPass::getAnalysisUsage(AU);
-    }
-  };
-
-  char MSAH::ID = 0;
-}
-
-FunctionPass*
-llvm::createX86MaxStackAlignmentHeuristicPass() { return new MSAH(); }
diff --git a/lib/Target/X86/X86TargetMachine.cpp b/lib/Target/X86/X86TargetMachine.cpp
index 158f9dc066..7ee9408f8b 100644
--- a/lib/Target/X86/X86TargetMachine.cpp
+++ b/lib/Target/X86/X86TargetMachine.cpp
@@ -171,7 +171,6 @@ bool X86PassConfig::addInstSelector() {
 }
 
 bool X86PassConfig::addPreRegAlloc() {
-  addPass(createX86MaxStackAlignmentHeuristicPass());
   return false;  // -print-machineinstr shouldn't print after this.
 }