Factor the stack alignment calculations out into a target independent pass.
No functionality change.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@90336 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/MaxStackAlignment.cpp b/lib/CodeGen/MaxStackAlignment.cpp
new file mode 100644
index 0000000..d327cfa
--- /dev/null
+++ b/lib/CodeGen/MaxStackAlignment.cpp
@@ -0,0 +1,70 @@
+//===-- MaxStackAlignment.cpp - Compute the required stack alignment -- ---===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass looks for vector register usage and aligned local objects to
+// calculate the maximum required alignment for a function. This is used by
+// targets which support it to determine if dynamic stack realignment is
+// necessary.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineFrameInfo.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/CodeGen/Passes.h"
+
+using namespace llvm;
+
+namespace {
+ struct MaximalStackAlignmentCalculator : public MachineFunctionPass {
+ static char ID;
+ MaximalStackAlignmentCalculator() : MachineFunctionPass(&ID) {}
+
+ virtual bool runOnMachineFunction(MachineFunction &MF) {
+ MachineFrameInfo *FFI = MF.getFrameInfo();
+ MachineRegisterInfo &RI = MF.getRegInfo();
+
+ // Calculate max stack alignment of all already allocated stack objects.
+ FFI->calculateMaxStackAlignment();
+ unsigned MaxAlign = FFI->getMaxAlignment();
+
+ // Be over-conservative: scan over all vreg defs and find whether vector
+ // registers are used. If yes, there is probability that vector registers
+ // will be spilled and thus the stack needs to be aligned properly.
+ // FIXME: It would be better to only do this if a spill actually
+ // happens rather than conseratively aligning the stack regardless.
+ for (unsigned RegNum = TargetRegisterInfo::FirstVirtualRegister;
+ RegNum < RI.getLastVirtReg(); ++RegNum)
+ MaxAlign = std::max(MaxAlign, RI.getRegClass(RegNum)->getAlignment());
+
+ if (FFI->getMaxAlignment() == MaxAlign)
+ return false;
+
+ FFI->setMaxAlignment(MaxAlign);
+ return true;
+ }
+
+ virtual const char *getPassName() const {
+ return "Stack Alignment Requirements Auto-Detector";
+ }
+
+ virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.setPreservesCFG();
+ MachineFunctionPass::getAnalysisUsage(AU);
+ }
+ };
+
+ char MaximalStackAlignmentCalculator::ID = 0;
+}
+
+FunctionPass*
+llvm::createMaxStackAlignmentCalculatorPass() {
+ return new MaximalStackAlignmentCalculator();
+}
+