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PPC: Support dynamic allocas with large alignment 

Support for dynamic stack alignments in the PPC backend has been unfinished, in
part because it depends on dynamic stack realignment (which I only just
recently implemented fully). Now we can also support dynamic allocas with
higher than the default target stack alignment (16 bytes).

In order to round-up the requested size to the maximum requested alignment, we
need an additional register to hold the rounded-up size. We're already using one
scavenged register to hold the previous stack-pointer value (which needs to be
stored with the signal-safe stdux update), and so when we have dynamic allocas
and a large alignment, we allocate two emergency spill slots for the scavenger.

llvm-svn: 186562
This commit is contained in:
Hal Finkel 2013-07-18 04:28:21 +00:00
parent 213c4cb18c
commit 1860763c76
3 changed files with 92 additions and 27 deletions
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6
llvm/lib/Target/PowerPC/PPCFrameLowering.cpp
View File

@ -1237,8 +1237,12 @@ PPCFrameLowering::addScavengingSpillSlot(MachineFunction &MF,
RC->getAlignment(),
false));
// Might we have over-aligned allocas?
bool HasAlVars = MFI->hasVarSizedObjects() &&
MFI->getMaxAlignment() > getStackAlignment();
// These kinds of spills might need two registers.
if (spillsCR(MF) || spillsVRSAVE(MF))
if (spillsCR(MF) || spillsVRSAVE(MF) || HasAlVars)
RS->addScavengingFrameIndex(MFI->CreateStackObject(RC->getSize(),
RC->getAlignment(),
false));

60
llvm/lib/Target/PowerPC/PPCRegisterInfo.cpp
View File

@ -269,8 +269,8 @@ void PPCRegisterInfo::lowerDynamicAlloc(MachineBasicBlock::iterator II) const {
// Get stack alignments.
unsigned TargetAlign = MF.getTarget().getFrameLowering()->getStackAlignment();
unsigned MaxAlign = MFI->getMaxAlignment();
if (MaxAlign > TargetAlign)
report_fatal_error("Dynamic alloca with large aligns not supported");
assert((maxCallFrameSize & (MaxAlign-1)) == 0 &&
"Maximum call-frame size not sufficiently aligned");
// Determine the previous frame's address. If FrameSize can't be
// represented as 16 bits or we need special alignment, then we load the
@ -296,39 +296,61 @@ void PPCRegisterInfo::lowerDynamicAlloc(MachineBasicBlock::iterator II) const {
.addReg(PPC::R1);
}
bool KillNegSizeReg = MI.getOperand(1).isKill();
unsigned NegSizeReg = MI.getOperand(1).getReg();
// Grow the stack and update the stack pointer link, then determine the
// address of new allocated space.
if (LP64) {
if (MaxAlign > TargetAlign) {
unsigned UnalNegSizeReg = NegSizeReg;
NegSizeReg = MF.getRegInfo().createVirtualRegister(G8RC);
// Unfortunately, there is no andi, only andi., and we can't insert that
// here because we might clobber cr0 while it is live.
BuildMI(MBB, II, dl, TII.get(PPC::LI8), NegSizeReg)
.addImm(~(MaxAlign-1));
unsigned NegSizeReg1 = NegSizeReg;
NegSizeReg = MF.getRegInfo().createVirtualRegister(G8RC);
BuildMI(MBB, II, dl, TII.get(PPC::AND8), NegSizeReg)
.addReg(UnalNegSizeReg, getKillRegState(KillNegSizeReg))
.addReg(NegSizeReg1, RegState::Kill);
KillNegSizeReg = true;
}
BuildMI(MBB, II, dl, TII.get(PPC::STDUX), PPC::X1)
.addReg(Reg, RegState::Kill)
.addReg(PPC::X1)
.addReg(MI.getOperand(1).getReg());
if (!MI.getOperand(1).isKill())
.addReg(NegSizeReg, getKillRegState(KillNegSizeReg));
BuildMI(MBB, II, dl, TII.get(PPC::ADDI8), MI.getOperand(0).getReg())
.addReg(PPC::X1)
.addImm(maxCallFrameSize);
else
// Implicitly kill the register.
BuildMI(MBB, II, dl, TII.get(PPC::ADDI8), MI.getOperand(0).getReg())
.addReg(PPC::X1)
.addImm(maxCallFrameSize)
.addReg(MI.getOperand(1).getReg(), RegState::ImplicitKill);
} else {
if (MaxAlign > TargetAlign) {
unsigned UnalNegSizeReg = NegSizeReg;
NegSizeReg = MF.getRegInfo().createVirtualRegister(GPRC);
// Unfortunately, there is no andi, only andi., and we can't insert that
// here because we might clobber cr0 while it is live.
BuildMI(MBB, II, dl, TII.get(PPC::LI), NegSizeReg)
.addImm(~(MaxAlign-1));
unsigned NegSizeReg1 = NegSizeReg;
NegSizeReg = MF.getRegInfo().createVirtualRegister(GPRC);
BuildMI(MBB, II, dl, TII.get(PPC::AND), NegSizeReg)
.addReg(UnalNegSizeReg, getKillRegState(KillNegSizeReg))
.addReg(NegSizeReg1, RegState::Kill);
KillNegSizeReg = true;
}
BuildMI(MBB, II, dl, TII.get(PPC::STWUX), PPC::R1)
.addReg(Reg, RegState::Kill)
.addReg(PPC::R1)
.addReg(MI.getOperand(1).getReg());
if (!MI.getOperand(1).isKill())
.addReg(NegSizeReg, getKillRegState(KillNegSizeReg));
BuildMI(MBB, II, dl, TII.get(PPC::ADDI), MI.getOperand(0).getReg())
.addReg(PPC::R1)
.addImm(maxCallFrameSize);
else
// Implicitly kill the register.
BuildMI(MBB, II, dl, TII.get(PPC::ADDI), MI.getOperand(0).getReg())
.addReg(PPC::R1)
.addImm(maxCallFrameSize)
.addReg(MI.getOperand(1).getReg(), RegState::ImplicitKill);
}
// Discard the DYNALLOC instruction.

39
llvm/test/CodeGen/PowerPC/dyn-alloca-aligned.ll Normal file
View File

@ -0,0 +1,39 @@
; RUN: llc -mtriple=powerpc64-unknown-linux-gnu -mcpu=pwr7 < %s | FileCheck %s
target datalayout = "E-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-f128:128:128-v128:128:128-n32:64"
target triple = "powerpc64-unknown-linux-gnu"
%struct.s = type { i32, i32 }
declare void @bar(i32*, i32*) #0
define void @goo(%struct.s* byval nocapture readonly %a, i32 signext %n) #0 {
entry:
%0 = zext i32 %n to i64
%vla = alloca i32, i64 %0, align 128
%vla1 = alloca i32, i64 %0, align 128
%a2 = getelementptr inbounds %struct.s* %a, i64 0, i32 0
%1 = load i32* %a2, align 4, !tbaa !0
store i32 %1, i32* %vla1, align 128, !tbaa !0
%b = getelementptr inbounds %struct.s* %a, i64 0, i32 1
%2 = load i32* %b, align 4, !tbaa !0
%arrayidx3 = getelementptr inbounds i32* %vla1, i64 1
store i32 %2, i32* %arrayidx3, align 4, !tbaa !0
call void @bar(i32* %vla1, i32* %vla) #0
ret void
; CHECK-LABEL: @goo
; CHECK-DAG: li [[REG1:[0-9]+]], -128
; CHECK-DAG: neg [[REG2:[0-9]+]],
; CHECK: and [[REG1]], [[REG2]], [[REG1]]
; CHECK: stdux {{[0-9]+}}, 1, [[REG1]]
; CHECK: blr
}
attributes #0 = { nounwind }
!0 = metadata !{metadata !"int", metadata !1}
!1 = metadata !{metadata !"omnipotent char", metadata !2}
!2 = metadata !{metadata !"Simple C/C++ TBAA"}