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Disable prolog code that aligns the stack when a

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local object of >16 byte alignment exists.  It does not
work and getting it to work is not trivial, as explained
in the comment.  This fixes all the remaining ppc32
failures in the struct-layout-1 part of the gcc testsuite.

(gcc does not support this either, and the only way to
get such an object is with __attribute__((aligned)) or
generic vectors; it can't be done in a standard-conforming
program, or with Altivec.  So I think disabling it is OK.)



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@48188 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dale Johannesen 2008-03-10 22:59:46 +00:00
parent 2b65c4e7cc
commit 82e4289fc7
1 changed files with 17 additions and 7 deletions
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24
lib/Target/PowerPC/PPCRegisterInfo.cpp
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@ -42,6 +42,16 @@
#include <cstdlib>
using namespace llvm;
// FIXME This disables some code that aligns the stack to a boundary
// bigger than the default (16 bytes on Darwin) when there is a stack local
// of greater alignment. This does not currently work, because the delta
// between old and new stack pointers is added to offsets that reference
// incoming parameters after the prolog is generated, and the code that
// does that doesn't handle a variable delta. You don't want to do that
// anyway; a better approach is to reserve another register that retains
// to the incoming stack pointer, and reference parameters relative to that.
#define ALIGN_STACK 0
// FIXME (64-bit): Eventually enable by default.
cl::opt<bool> EnablePPC32RS("enable-ppc32-regscavenger",
cl::init(false),
@ -858,10 +868,10 @@ void PPCRegisterInfo::determineFrameLayout(MachineFunction &MF) const {
// If we are a leaf function, and use up to 224 bytes of stack space,
// don't have a frame pointer, calls, or dynamic alloca then we do not need
// to adjust the stack pointer (we fit in the Red Zone).
if (FrameSize <= 224 && // Fits in red zone.
!MFI->hasVarSizedObjects() && // No dynamic alloca.
!MFI->hasCalls() && // No calls.
MaxAlign <= TargetAlign) { // No special alignment.
if (FrameSize <= 224 && // Fits in red zone.
!MFI->hasVarSizedObjects() && // No dynamic alloca.
!MFI->hasCalls() && // No calls.
(!ALIGN_STACK || MaxAlign <= TargetAlign)) { // No special alignment.
// No need for frame
MFI->setStackSize(0);
return;
@ -1028,7 +1038,7 @@ PPCRegisterInfo::emitPrologue(MachineFunction &MF) const {
// If there is a preferred stack alignment, align R1 now
if (!IsPPC64) {
// PPC32.
if (MaxAlign > TargetAlign) {
if (ALIGN_STACK && MaxAlign > TargetAlign) {
assert(isPowerOf2_32(MaxAlign)&&isInt16(MaxAlign)&&"Invalid alignment!");
assert(isInt16(NegFrameSize) && "Unhandled stack size and alignment!");
@ -1061,7 +1071,7 @@ PPCRegisterInfo::emitPrologue(MachineFunction &MF) const {
.addReg(PPC::R0);
}
} else { // PPC64.
if (MaxAlign > TargetAlign) {
if (ALIGN_STACK && MaxAlign > TargetAlign) {
assert(isPowerOf2_32(MaxAlign)&&isInt16(MaxAlign)&&"Invalid alignment!");
assert(isInt16(NegFrameSize) && "Unhandled stack size and alignment!");
@ -1182,7 +1192,7 @@ void PPCRegisterInfo::emitEpilogue(MachineFunction &MF,
// The loaded (or persistent) stack pointer value is offset by the 'stwu'
// on entry to the function. Add this offset back now.
if (!Subtarget.isPPC64()) {
if (isInt16(FrameSize) && TargetAlign >= MaxAlign &&
if (isInt16(FrameSize) && (!ALIGN_STACK || TargetAlign >= MaxAlign) &&
!MFI->hasVarSizedObjects()) {
BuildMI(MBB, MBBI, TII.get(PPC::ADDI), PPC::R1)
.addReg(PPC::R1).addImm(FrameSize);