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[AArch64] Fix crash with empty/pseudo-only blocks in A53 erratum (835769) workaround

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llvm-svn: 219684
This commit is contained in:
Bradley Smith 2014-10-14 14:02:41 +00:00
parent ad195b7bc4
commit bb04f108aa
2 changed files with 35 additions and 15 deletions
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41
lib/Target/AArch64/AArch64A53Fix835769.cpp
View File

@ -123,20 +123,20 @@ AArch64A53Fix835769::runOnMachineFunction(MachineFunction &F) {
// Return the block that was fallen through to get to MBB, if any,
// otherwise nullptr.
static MachineBasicBlock *getBBFallenThrough(MachineBasicBlock &MBB,
static MachineBasicBlock *getBBFallenThrough(MachineBasicBlock *MBB,
const TargetInstrInfo *TII) {
// Get the previous machine basic block in the function.
MachineFunction::iterator MBBI = MBB;
MachineFunction::iterator MBBI = *MBB;
// Can't go off top of function.
if (MBBI == MBB.getParent()->begin())
if (MBBI == MBB->getParent()->begin())
return nullptr;
MachineBasicBlock *TBB = nullptr, *FBB = nullptr;
SmallVector<MachineOperand, 2> Cond;
MachineBasicBlock *PrevBB = std::prev(MBBI);
for (MachineBasicBlock *S : MBB.predecessors())
for (MachineBasicBlock *S : MBB->predecessors())
if (S == PrevBB && !TII->AnalyzeBranch(*PrevBB, TBB, FBB, Cond) &&
!TBB && !FBB)
return S;
@ -144,13 +144,25 @@ static MachineBasicBlock *getBBFallenThrough(MachineBasicBlock &MBB,
return nullptr;
}
static MachineInstr *getLastNonPseudo(MachineBasicBlock *MBB) {
for (auto I = MBB->rbegin(), E = MBB->rend(); I != E; ++I) {
if (!I->isPseudo())
return &*I;
// Iterate through fallen through blocks trying to find a previous non-pseudo if
// there is one, otherwise return nullptr. Only look for instructions in
// previous blocks, not the current block, since we only use this to look at
// previous blocks.
static MachineInstr *getLastNonPseudo(MachineBasicBlock &MBB,
const TargetInstrInfo *TII) {
MachineBasicBlock *FMBB = &MBB;
// If there is no non-pseudo in the current block, loop back around and try
// the previous block (if there is one).
while ((FMBB = getBBFallenThrough(FMBB, TII))) {
for (auto I = FMBB->rbegin(), E = FMBB->rend(); I != E; ++I) {
if (!I->isPseudo())
return &*I;
}
}
llvm_unreachable("Expected to find a non-pseudo instruction");
// There was no previous non-pseudo in the fallen through blocks
return nullptr;
}
static void insertNopBeforeInstruction(MachineBasicBlock &MBB, MachineInstr* MI,
@ -158,12 +170,10 @@ static void insertNopBeforeInstruction(MachineBasicBlock &MBB, MachineInstr* MI,
// If we are the first instruction of the block, put the NOP at the end of
// the previous fallthrough block
if (MI == &MBB.front()) {
MachineBasicBlock *PMBB = getBBFallenThrough(MBB, TII);
assert(PMBB && "Expected basic block");
MachineInstr *I = getLastNonPseudo(PMBB);
MachineInstr *I = getLastNonPseudo(MBB, TII);
assert(I && "Expected instruction");
DebugLoc DL = I->getDebugLoc();
BuildMI(PMBB, DL, TII->get(AArch64::HINT)).addImm(0);
BuildMI(I->getParent(), DL, TII->get(AArch64::HINT)).addImm(0);
}
else {
DebugLoc DL = MI->getDebugLoc();
@ -186,8 +196,9 @@ AArch64A53Fix835769::runOnBasicBlock(MachineBasicBlock &MBB) {
unsigned Idx = 0;
MachineInstr *PrevInstr = nullptr;
if (MachineBasicBlock *PMBB = getBBFallenThrough(MBB, TII))
PrevInstr = getLastNonPseudo(PMBB);
// Try and find the last non-pseudo instruction in any fallen through blocks,
// if there isn't one, then we use nullptr to represent that.
PrevInstr = getLastNonPseudo(MBB, TII);
for (auto &MI : MBB) {
MachineInstr *CurrInstr = &MI;

9
test/CodeGen/AArch64/aarch64-fix-cortex-a53-835769.ll
View File

@ -516,6 +516,15 @@ block1:
; CHECK-NOWORKAROUND-NEXT: BB
; CHECK-NOWORKAROUND-NEXT: madd
; No checks for this, just check it doesn't crash
define i32 @crash_check(i8** nocapture readnone %data) #0 {
entry:
br label %while.cond
while.cond:
br label %while.cond
}
attributes #0 = { nounwind readonly "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
attributes #1 = { nounwind "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
attributes #2 = { nounwind }