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Enforce stricter liveness rules for PHIs.

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Verify that all paths from the entry block to a virtual register read
pass through a def. Enable this check even when MRI->isSSA() is false.

Verify that the live range of a virtual register is live out of all
predecessor blocks, even for PHI-values.

This requires that PHIElimination sometimes inserts IMPLICIT_DEF
instruction in predecessor blocks.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@159150 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Jakob Stoklund Olesen 2012-06-25 18:18:27 +00:00
parent 5984d2b31f
commit a4e6397fd9
2 changed files with 37 additions and 6 deletions
lib/CodeGen
MachineVerifier.cpp
test/CodeGen/Generic
undef-phi.ll

17
lib/CodeGen/MachineVerifier.cpp

@ -1049,7 +1049,7 @@ void MachineVerifier::visitMachineFunctionAfter() {
// Now check liveness info if available
calcRegsRequired();
if (MRI->isSSA() && !MF->empty()) {
if (!MF->empty()) {
BBInfo &MInfo = MBBInfoMap[&MF->front()];
for (RegSet::iterator
I = MInfo.vregsRequired.begin(), E = MInfo.vregsRequired.end(); I != E;
@ -1332,15 +1332,18 @@ void MachineVerifier::verifyLiveIntervals() {
++MFI;
continue;
}
// Is VNI a PHI-def in the current block?
bool IsPHI = VNI->isPHIDef() &&
VNI->def == LiveInts->getMBBStartIdx(MFI);
// Check that VNI is live-out of all predecessors.
for (MachineBasicBlock::const_pred_iterator PI = MFI->pred_begin(),
PE = MFI->pred_end(); PI != PE; ++PI) {
SlotIndex PEnd = LiveInts->getMBBEndIdx(*PI);
const VNInfo *PVNI = LI.getVNInfoBefore(PEnd);
if (VNI->isPHIDef() && VNI->def == LiveInts->getMBBStartIdx(MFI))
continue;
// All predecessors must have a live-out value.
if (!PVNI) {
report("Register not marked live out of predecessor", *PI);
*OS << "Valno #" << VNI->id << " live into BB#" << MFI->getNumber()
@ -1349,12 +1352,14 @@ void MachineVerifier::verifyLiveIntervals() {
continue;
}
if (PVNI != VNI) {
// Only PHI-defs can take different predecessor values.
if (!IsPHI && PVNI != VNI) {
report("Different value live out of predecessor", *PI);
*OS << "Valno #" << PVNI->id << " live out of BB#"
<< (*PI)->getNumber() << '@' << PEnd
<< "\nValno #" << VNI->id << " live into BB#" << MFI->getNumber()
<< '@' << LiveInts->getMBBStartIdx(MFI) << " in " << LI << '\n';
<< '@' << LiveInts->getMBBStartIdx(MFI) << " in "
<< PrintReg(Reg) << ": " << LI << '\n';
}
}
if (&*MFI == EndMBB)

26
test/CodeGen/Generic/undef-phi.ll Normal file

@ -0,0 +1,26 @@
; RUN: llc < %s -verify-machineinstrs -verify-coalescing
;
; This function has a PHI with one undefined input. Verify that PHIElimination
; inserts an IMPLICIT_DEF instruction in the predecessor so all paths to the use
; pass through a def.
%struct.xx_stack = type { i32, %struct.xx_stack* }
define i32 @push(%struct.xx_stack* %stack) nounwind uwtable readonly ssp {
entry:
%tobool1 = icmp eq %struct.xx_stack* %stack, null
br i1 %tobool1, label %for.end, label %for.body
for.body:
%stack.addr.02 = phi %struct.xx_stack* [ %0, %for.body ], [ %stack, %entry ]
%next = getelementptr inbounds %struct.xx_stack* %stack.addr.02, i64 0, i32 1
%0 = load %struct.xx_stack** %next, align 8
%tobool = icmp eq %struct.xx_stack* %0, null
br i1 %tobool, label %for.end, label %for.body
for.end:
%top.0.lcssa = phi %struct.xx_stack* [ undef, %entry ], [ %stack.addr.02, %for.body ]
%first = getelementptr inbounds %struct.xx_stack* %top.0.lcssa, i64 0, i32 0
%1 = load i32* %first, align 4
ret i32 %1
}