Add support for dynamic stack realignment in the presence of dynamic allocas on
X86. Basically, this is a reapplication of r158087 with a few fixes.
Specifically, (1) the stack pointer is restored from the base pointer before
popping callee-saved registers and (2) in obscure cases (see comments in patch)
we must cache the value of the original stack adjustment in the prologue and
apply it in the epilogue.
rdar://11496434
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@160002 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86FrameLowering.cpp b/lib/Target/X86/X86FrameLowering.cpp
index 7e7f364..21ad062 100644
--- a/lib/Target/X86/X86FrameLowering.cpp
+++ b/lib/Target/X86/X86FrameLowering.cpp
@@ -650,6 +650,7 @@
unsigned SlotSize = RegInfo->getSlotSize();
unsigned FramePtr = RegInfo->getFrameRegister(MF);
unsigned StackPtr = RegInfo->getStackRegister();
+ unsigned BasePtr = RegInfo->getBaseRegister();
DebugLoc DL;
// If we're forcing a stack realignment we can't rely on just the frame
@@ -913,6 +914,20 @@
emitSPUpdate(MBB, MBBI, StackPtr, -(int64_t)NumBytes, Is64Bit,
UseLEA, TII, *RegInfo);
+ // If we need a base pointer, set it up here. It's whatever the value
+ // of the stack pointer is at this point. Any variable size objects
+ // will be allocated after this, so we can still use the base pointer
+ // to reference locals.
+ if (RegInfo->hasBasePointer(MF)) {
+ // Update the frame pointer with the current stack pointer.
+ unsigned Opc = Is64Bit ? X86::MOV64rr : X86::MOV32rr;
+ BuildMI(MBB, MBBI, DL, TII.get(Opc), BasePtr)
+ .addReg(StackPtr)
+ .setMIFlag(MachineInstr::FrameSetup);
+
+ MFI->setBasePtrStackAdjustment(NumBytes);
+ }
+
if (( (!HasFP && NumBytes) || PushedRegs) && needsFrameMoves) {
// Mark end of stack pointer adjustment.
MCSymbol *Label = MMI.getContext().CreateTempSymbol();
@@ -960,6 +975,7 @@
unsigned SlotSize = RegInfo->getSlotSize();
unsigned FramePtr = RegInfo->getFrameRegister(MF);
unsigned StackPtr = RegInfo->getStackRegister();
+ unsigned BasePtr = RegInfo->getBaseRegister();
switch (RetOpcode) {
default:
@@ -1029,6 +1045,15 @@
if (NumBytes || MFI->hasVarSizedObjects())
mergeSPUpdatesUp(MBB, MBBI, StackPtr, &NumBytes);
+ // Restore the SP from the BP, if necessary.
+ if (RegInfo->hasBasePointer(MF)) {
+ BuildMI(MBB, MBBI, DL, TII.get(Is64Bit ? X86::MOV64rr : X86::MOV32rr),
+ StackPtr).addReg(BasePtr);
+
+ // When restoring from the BP we must use a cached SP adjustment.
+ NumBytes = MFI->getBasePtrStackAdjustment();
+ }
+
// If dynamic alloca is used, then reset esp to point to the last callee-saved
// slot before popping them off! Same applies for the case, when stack was
// realigned.
@@ -1147,7 +1172,16 @@
int Offset = MFI->getObjectOffset(FI) - getOffsetOfLocalArea();
uint64_t StackSize = MFI->getStackSize();
- if (RegInfo->needsStackRealignment(MF)) {
+ if (RegInfo->hasBasePointer(MF)) {
+ assert (hasFP(MF) && "VLAs and dynamic stack realign, but no FP?!");
+ if (FI < 0) {
+ // Skip the saved EBP.
+ return Offset + RegInfo->getSlotSize();
+ } else {
+ assert((-(Offset + StackSize)) % MFI->getObjectAlignment(FI) == 0);
+ return Offset + StackSize;
+ }
+ } else if (RegInfo->needsStackRealignment(MF)) {
if (FI < 0) {
// Skip the saved EBP.
return Offset + RegInfo->getSlotSize();
@@ -1178,9 +1212,14 @@
const X86RegisterInfo *RegInfo =
static_cast<const X86RegisterInfo*>(MF.getTarget().getRegisterInfo());
// We can't calculate offset from frame pointer if the stack is realigned,
- // so enforce usage of stack pointer.
- FrameReg = (RegInfo->needsStackRealignment(MF)) ?
- RegInfo->getStackRegister() : RegInfo->getFrameRegister(MF);
+ // so enforce usage of stack/base pointer. The base pointer is used when we
+ // have dynamic allocas in addition to dynamic realignment.
+ if (RegInfo->hasBasePointer(MF))
+ FrameReg = RegInfo->getBaseRegister();
+ else if (RegInfo->needsStackRealignment(MF))
+ FrameReg = RegInfo->getStackRegister();
+ else
+ FrameReg = RegInfo->getFrameRegister(MF);
return getFrameIndexOffset(MF, FI);
}
@@ -1317,6 +1356,10 @@
"Slot for EBP register must be last in order to be found!");
(void)FrameIdx;
}
+
+ // Spill the BasePtr if it's used.
+ if (RegInfo->hasBasePointer(MF))
+ MF.getRegInfo().setPhysRegUsed(RegInfo->getBaseRegister());
}
static bool