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[machineverifier] Detect PHI's that are preceeded by non-PHI's

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If present, PHI nodes must appear before non-PHI nodes in a basic block. The
register allocator relies on this and will fail to eliminate PHI's that do not
meet this requirement.

llvm-svn: 343731
This commit is contained in:
Daniel Sanders 2018-10-03 22:05:31 +00:00
parent 08010823f4
commit 8c0f7d8314
2 changed files with 95 additions and 3 deletions
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14
lib/CodeGen/MachineVerifier.cpp
View File

@ -109,6 +109,7 @@ namespace {
using RegMap = DenseMap<unsigned, const MachineInstr *>;
using BlockSet = SmallPtrSet<const MachineBasicBlock *, 8>;
const MachineInstr *FirstNonPHI;
const MachineInstr *FirstTerminator;
BlockSet FunctionBlocks;
@ -608,6 +609,7 @@ static bool matchPair(MachineBasicBlock::const_succ_iterator i,
void
MachineVerifier::visitMachineBasicBlockBefore(const MachineBasicBlock *MBB) {
FirstTerminator = nullptr;
FirstNonPHI = nullptr;
if (!MF->getProperties().hasProperty(
MachineFunctionProperties::Property::NoPHIs) && MRI->tracksLiveness()) {
@ -889,9 +891,15 @@ void MachineVerifier::visitMachineInstrBefore(const MachineInstr *MI) {
<< MI->getNumOperands() << " given.\n";
}
if (MI->isPHI() && MF->getProperties().hasProperty(
MachineFunctionProperties::Property::NoPHIs))
report("Found PHI instruction with NoPHIs property set", MI);
if (MI->isPHI()) {
if (MF->getProperties().hasProperty(
MachineFunctionProperties::Property::NoPHIs))
report("Found PHI instruction with NoPHIs property set", MI);
if (FirstNonPHI)
report("Found PHI instruction after non-PHI", MI);
} else if (FirstNonPHI == nullptr)
FirstNonPHI = MI;
// Check the tied operands.
if (MI->isInlineAsm())

84
test/Verifier/test_phis_precede_nonphis.mir Normal file
View File

@ -0,0 +1,84 @@
# RUN: not llc -run-pass=machineverifier %s -o - 2>&1 | FileCheck %s
# REQUIRES: aarch64-registered-target
--- |
target datalayout = "e-m:o-i64:64-i128:128-n32:64-S128"
target triple = "aarch64--"
define void @valid(i8* %addr) {
entry:
br i1 0, label %if, label %else
if:
br label %exit
else:
br label %exit
exit:
ret void
}
define void @broken(i8* %addr) {
entry:
br i1 0, label %if, label %exit
if:
br label %exit
exit:
ret void
}
...
---
name: valid
tracksRegLiveness: true
body: |
bb.0.entry:
liveins: $w1
successors: %bb.1(0x40000000), %bb.2(0x40000000); %bb.1(50.00%), %bb.2(50.00%)
%1:_(s32) = COPY $w1
%2:_(s32) = G_CONSTANT i32 1
%3:_(s1) = G_ICMP intpred(ne), %1:_(s32), %2:_
G_BRCOND %3:_(s1), %bb.1
G_BR %bb.2.else
bb.1.if:
successors: %bb.3(0x80000000)
%4:_(s32) = G_CONSTANT i32 1
%5:_(s8) = G_TRUNC %4
G_BR %bb.3.exit
bb.2.else:
successors: %bb.3(0x80000000)
%6:_(s32) = G_CONSTANT i8 1
%7:_(s8) = G_TRUNC %6
G_BR %bb.3.exit
bb.3.exit:
%8:_(s8) = G_PHI %5:_(s8), %bb.1, %7:_(s8), %bb.2
%9:_(s32) = G_ZEXT %8
$w1 = COPY %9
...
---
name: broken
tracksRegLiveness: true
body: |
bb.0.entry:
liveins: $w1
successors: %bb.1(0x40000000), %bb.2(0x40000000); %bb.1(50.00%), %bb.2(50.00%)
%1:_(s32) = COPY $w1
%2:_(s32) = G_CONSTANT i32 1
%3:_(s1) = G_ICMP intpred(ne), %1:_(s32), %2:_
%4:_(s32) = G_CONSTANT i32 1
%6:_(s8) = G_CONSTANT i8 2
G_BRCOND %3:_(s1), %bb.1
G_BR %bb.2.exit
bb.1.if:
successors: %bb.2(0x80000000)
G_BR %bb.2.exit
bb.2.exit:
%5:_(s8) = G_TRUNC %4
%8:_(s8) = G_PHI %5:_(s8), %bb.0, %6:_(s8), %bb.1
%9:_(s32) = G_ZEXT %8
$w1 = COPY %9
...
# CHECK-NOT: Bad machine code
# CHECK-LABEL: Bad machine code: Found PHI instruction after non-PHI
# CHECK-NEXT: - function: broken
# CHECK-NEXT: - basic block: %bb.2 exit
# CHECK-NEXT: - instruction: %6:_(s8) = G_PHI %5:_(s8), %bb.0, %4:_(s8), %bb.1
# CHECK-NOT: Bad machine code