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Add an option to always emit realignment code for a particular module. 

llvm-svn: 110404
This commit is contained in:
Eric Christopher 2010-08-05 23:57:43 +00:00
parent 01a81b01bc
commit e1fb772aa5
2 changed files with 55 additions and 1 deletions
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35
llvm/lib/Target/X86/X86RegisterInfo.cpp
View File

@ -38,8 +38,15 @@
#include "llvm/ADT/BitVector.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/CommandLine.h"
using namespace llvm;
static cl::opt<bool>
ForceStackAlign("force-align-stack",
cl::desc("Force align the stack to the minimum alignment"
" needed for the function."),
cl::init(false), cl::Hidden);
X86RegisterInfo::X86RegisterInfo(X86TargetMachine &tm,
const TargetInstrInfo &tii)
: X86GenRegisterInfo(tm.getSubtarget<X86Subtarget>().is64Bit() ?
@ -471,7 +478,11 @@ bool X86RegisterInfo::needsStackRealignment(const MachineFunction &MF) const {
if (0 && requiresRealignment && MFI->hasVarSizedObjects())
report_fatal_error(
"Stack realignment in presense of dynamic allocas is not supported");
// If we've requested that we force align the stack do so now.
if (ForceStackAlign)
return canRealignStack(MF);
return requiresRealignment && canRealignStack(MF);
}
@ -906,6 +917,17 @@ void X86RegisterInfo::emitPrologue(MachineFunction &MF) const {
bool HasFP = hasFP(MF);
DebugLoc DL;
// If we're forcing a stack realignment we can't rely on just the frame
// info, we need to know the ABI stack alignment as well in case we
// have a call out. Otherwise just make sure we have some alignment - we'll
// go with the minimum SlotSize.
if (ForceStackAlign) {
if (MFI->hasCalls())
MaxAlign = (StackAlign > MaxAlign) ? StackAlign : MaxAlign;
else if (MaxAlign < SlotSize)
MaxAlign = SlotSize;
}
// Add RETADDR move area to callee saved frame size.
int TailCallReturnAddrDelta = X86FI->getTCReturnAddrDelta();
if (TailCallReturnAddrDelta < 0)
@ -1177,6 +1199,17 @@ void X86RegisterInfo::emitEpilogue(MachineFunction &MF,
unsigned CSSize = X86FI->getCalleeSavedFrameSize();
uint64_t NumBytes = 0;
// If we're forcing a stack realignment we can't rely on just the frame
// info, we need to know the ABI stack alignment as well in case we
// have a call out. Otherwise just make sure we have some alignment - we'll
// go with the minimum.
if (ForceStackAlign) {
if (MFI->hasCalls())
MaxAlign = (StackAlign > MaxAlign) ? StackAlign : MaxAlign;
else
MaxAlign = MaxAlign ? MaxAlign : 4;
}
if (hasFP(MF)) {
// Calculate required stack adjustment.
uint64_t FrameSize = StackSize - SlotSize;

21
llvm/test/CodeGen/X86/force-align-stack.ll Normal file
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@ -0,0 +1,21 @@
; RUN: llc < %s -relocation-model=static -force-align-stack | FileCheck %s
; Tests to make sure that we always align the stack out to the minimum needed -
; in this case 16-bytes.
target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128-n8:16:32"
target triple = "i386-apple-darwin10.3"
define void @a() nounwind ssp {
entry:
; CHECK: _a:
; CHECK: andl $-16, %esp
%z = alloca <16 x i8> ; <<16 x i8>*> [#uses=2]
%"alloca point" = bitcast i32 0 to i32 ; <i32> [#uses=0]
store <16 x i8> zeroinitializer, <16 x i8>* %z, align 16
call void @b(<16 x i8>* %z) nounwind
br label %return
return: ; preds = %entry
ret void
}
declare void @b(<16 x i8>*)