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[llvm-exegesis] Fix serialization/deserialization of special NoRegister register (PR41448) 

Summary:
A *lot* of instructions have this special register.
It seems this never really worked, but i finally noticed it only
because it happened to break for `CMOV16rm` instruction.

We serialized that register as "" (empty string), which is naturally
'ignored' during deserialization, so we re-create a `MCInst` with
too few operands.

And when we then happened to try to resolve variant sched class
for this mis-serialized instruction, and the variant predicate
tried to read an operand that was out of bounds since we got less operands,
we crashed.

Fixes [[ https://bugs.llvm.org/show_bug.cgi?id=41448 | PR41448 ]].

Reviewers: craig.topper, courbet

Reviewed By: courbet

Subscribers: tschuett, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D60517

llvm-svn: 358153
This commit is contained in:
Roman Lebedev 2019-04-11 07:20:50 +00:00
parent 58c080a3b1
commit fbb823891d
2 changed files with 31 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
llvm/test/tools/llvm-exegesis/X86/uops-CMOV16rm-noreg.s Normal file
View File

@ -0,0 +1,17 @@
# RUN: llvm-exegesis -mode=uops -opcode-name=CMOV16rm -benchmarks-file=%t.CMOV16rm-uops.yaml
# RUN: FileCheck -check-prefixes=CHECK-YAML -input-file=%t.CMOV16rm-uops.yaml %s
# RUN: llvm-exegesis -mcpu=bdver2 -mode=analysis -benchmarks-file=%t.CMOV16rm-uops.yaml -analysis-clusters-output-file=- -analysis-clustering-epsilon=0.1 -analysis-inconsistency-epsilon=0.1 -analysis-numpoints=1 -analysis-clustering=naive | FileCheck -check-prefixes=CHECK-CLUSTERS %s
# https://bugs.llvm.org/show_bug.cgi?id=41448
# 1. Verify that we correctly serialize RegNo 0 as %noreg, not as an empty string!
# 2. Verify that deserialization works. Since CMOV16rm has a variant sched class, just printing clusters is sufficient
CHECK-YAML: ---
CHECK-YAML-NEXT: mode: uops
CHECK-YAML-NEXT: key:
CHECK-YAML-NEXT: instructions:
CHECK-YAML-NEXT: - 'CMOV16rm {{[A-Z0-9]+}} {{[A-Z0-9]+}} {{[A-Z0-9]+}} i_0x1 %noreg i_0x0 %noreg i_0x{{[0-9a-f]}}'
CHECK-YAML-LAST: ...
# CHECK-CLUSTERS: {{^}}cluster_id,opcode_name,config,sched_class,
# CHECK-CLUSTERS-NEXT: {{^}}0,

21
llvm/tools/llvm-exegesis/lib/BenchmarkResult.cpp
View File

@ -21,6 +21,7 @@
static constexpr const char kIntegerPrefix[] = "i_0x";
static constexpr const char kDoublePrefix[] = "f_";
static constexpr const char kInvalidOperand[] = "INVALID";
static constexpr llvm::StringLiteral kNoRegister("%noreg");
namespace llvm {
@ -47,7 +48,9 @@ struct YamlContext {
llvm::StringMap<unsigned>
generateRegNameToRegNoMapping(const llvm::MCRegisterInfo &RegInfo) {
llvm::StringMap<unsigned> Map(RegInfo.getNumRegs());
for (unsigned I = 0, E = RegInfo.getNumRegs(); I < E; ++I)
// Special-case RegNo 0, which would otherwise be spelled as ''.
Map[kNoRegister] = 0;
for (unsigned I = 1, E = RegInfo.getNumRegs(); I < E; ++I)
Map[RegInfo.getName(I)] = I;
assert(Map.size() == RegInfo.getNumRegs() && "Size prediction failed");
return Map;
@ -83,18 +86,21 @@ struct YamlContext {
llvm::raw_string_ostream &getErrorStream() { return ErrorStream; }
llvm::StringRef getRegName(unsigned RegNo) {
// Special case: RegNo 0 is NoRegister. We have to deal with it explicitly.
if (RegNo == 0)
return kNoRegister;
const llvm::StringRef RegName = State->getRegInfo().getName(RegNo);
if (RegName.empty())
ErrorStream << "No register with enum value '" << RegNo << "'\n";
return RegName;
}
unsigned getRegNo(llvm::StringRef RegName) {
llvm::Optional<unsigned> getRegNo(llvm::StringRef RegName) {
auto Iter = RegNameToRegNo.find(RegName);
if (Iter != RegNameToRegNo.end())
return Iter->second;
ErrorStream << "No register with name '" << RegName << "'\n";
return 0;
return llvm::None;
}
private:
@ -142,8 +148,8 @@ private:
return llvm::MCOperand::createImm(IntValue);
if (tryDeserializeFPOperand(String, DoubleValue))
return llvm::MCOperand::createFPImm(DoubleValue);
if (unsigned RegNo = getRegNo(String))
return llvm::MCOperand::createReg(RegNo);
if (auto RegNo = getRegNo(String))
return llvm::MCOperand::createReg(*RegNo);
if (String != kInvalidOperand)
ErrorStream << "Unknown Operand: '" << String << "'\n";
return {};
@ -258,8 +264,9 @@ template <> struct ScalarTraits<exegesis::RegisterValue> {
String.split(Pieces, "=0x", /* MaxSplit */ -1,
/* KeepEmpty */ false);
YamlContext &Context = getTypedContext(Ctx);
if (Pieces.size() == 2) {
RV.Register = Context.getRegNo(Pieces[0]);
llvm::Optional<unsigned> RegNo;
if (Pieces.size() == 2 && (RegNo = Context.getRegNo(Pieces[0]))) {
RV.Register = *RegNo;
const unsigned BitsNeeded = llvm::APInt::getBitsNeeded(Pieces[1], kRadix);
RV.Value = llvm::APInt(BitsNeeded, Pieces[1], kRadix);
} else {