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[MC][X86] Enhance X86 Register expression handling to more closely match GCC.

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Allow the comparison of x86 registers in the evaluation of assembler
directives. This generalizes and simplifies the extension from r334022
to catch another case found in the Linux kernel.

Reviewers: rnk, void

Reviewed By: rnk

Subscribers: hiraditya, nickdesaulniers, llvm-commits

Differential Revision: https://reviews.llvm.org/D50795

llvm-svn: 339895
This commit is contained in:
Nirav Dave 2018-08-16 16:31:14 +00:00
parent d8420c8c15
commit 11c9c5b2e9
8 changed files with 56 additions and 32 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/llvm/MC/MCExpr.h
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@ -589,6 +589,8 @@ public:
virtual bool evaluateAsRelocatableImpl(MCValue &Res,
const MCAsmLayout *Layout,
const MCFixup *Fixup) const = 0;
// allow Target Expressions to be checked for equality
virtual bool isEqualTo(const MCExpr *x) const { return false; }
// This should be set when assigned expressions are not valid ".set"
// expressions, e.g. registers, and must be inlined.
virtual bool inlineAssignedExpr() const { return false; }

2
include/llvm/MC/MCParser/MCAsmParserUtils.h
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@ -25,7 +25,7 @@ namespace MCParserUtils {
/// On success, returns false and sets the Symbol and Value output parameters.
bool parseAssignmentExpression(StringRef Name, bool allow_redef,
MCAsmParser &Parser, MCSymbol *&Symbol,
const MCExpr *&Value, bool AllowExtendedExpr = false);
const MCExpr *&Value);
} // namespace MCParserUtils

6
include/llvm/MC/MCParser/MCTargetAsmParser.h
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@ -372,9 +372,9 @@ public:
SemaCallback = Callback;
}
// Target-specific parsing of assembler-level variable assignment.
virtual bool parseAssignmentExpression(const MCExpr *&Res, SMLoc &EndLoc) {
return getParser().parseExpression(Res, EndLoc);
// Target-specific parsing of expression.
virtual bool parsePrimaryExpr(const MCExpr *&Res, SMLoc &EndLoc) {
return getParser().parsePrimaryExpr(Res, EndLoc);
}
virtual bool ParseRegister(unsigned &RegNo, SMLoc &StartLoc,

16
lib/MC/MCExpr.cpp
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@ -751,8 +751,22 @@ bool MCExpr::evaluateAsRelocatableImpl(MCValue &Res, const MCAssembler *Asm,
if (!ABE->getLHS()->evaluateAsRelocatableImpl(LHSValue, Asm, Layout, Fixup,
Addrs, InSet) ||
!ABE->getRHS()->evaluateAsRelocatableImpl(RHSValue, Asm, Layout, Fixup,
Addrs, InSet))
Addrs, InSet)) {
// Check if both are Target Expressions, see if we can compare them.
if (const MCTargetExpr *L = dyn_cast<MCTargetExpr>(ABE->getLHS()))
if (const MCTargetExpr *R = cast<MCTargetExpr>(ABE->getRHS())) {
switch (ABE->getOpcode()) {
case MCBinaryExpr::EQ:
Res = MCValue::get((L->isEqualTo(R)) ? -1 : 0);
return true;
case MCBinaryExpr::NE:
Res = MCValue::get((R->isEqualTo(R)) ? 0 : -1);
return true;
default: {}
}
}
return false;
}
// We only support a few operations on non-constant expressions, handle
// those first.

23
lib/MC/MCParser/AsmParser.cpp
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@ -337,7 +337,7 @@ private:
StringRef parseStringToComma();
bool parseAssignment(StringRef Name, bool allow_redef,
bool NoDeadStrip = false, bool AllowExtendedExpr = false);
bool NoDeadStrip = false);
unsigned getBinOpPrecedence(AsmToken::TokenKind K,
MCBinaryExpr::Opcode &Kind);
@ -1363,7 +1363,8 @@ void AsmParser::altMacroString(StringRef AltMacroStr,std::string &Res) {
bool AsmParser::parseExpression(const MCExpr *&Res, SMLoc &EndLoc) {
// Parse the expression.
Res = nullptr;
if (parsePrimaryExpr(Res, EndLoc) || parseBinOpRHS(1, Res, EndLoc))
if (getTargetParser().parsePrimaryExpr(Res, EndLoc) ||
parseBinOpRHS(1, Res, EndLoc))
return true;
// As a special case, we support 'a op b @ modifier' by rewriting the
@ -1617,7 +1618,7 @@ bool AsmParser::parseBinOpRHS(unsigned Precedence, const MCExpr *&Res,
// Eat the next primary expression.
const MCExpr *RHS;
if (parsePrimaryExpr(RHS, EndLoc))
if (getTargetParser().parsePrimaryExpr(RHS, EndLoc))
return true;
// If BinOp binds less tightly with RHS than the operator after RHS, let
@ -1826,7 +1827,7 @@ bool AsmParser::parseStatement(ParseStatementInfo &Info,
// identifier '=' ... -> assignment statement
Lex();
return parseAssignment(IDVal, true, /*NoDeadStrip*/ false, /*AllowExtendedExpr*/true);
return parseAssignment(IDVal, true);
default: // Normal instruction or directive.
break;
@ -2766,11 +2767,11 @@ void AsmParser::handleMacroExit() {
}
bool AsmParser::parseAssignment(StringRef Name, bool allow_redef,
bool NoDeadStrip, bool AllowExtendedExpr) {
bool NoDeadStrip) {
MCSymbol *Sym;
const MCExpr *Value;
if (MCParserUtils::parseAssignmentExpression(Name, allow_redef, *this, Sym,
Value, AllowExtendedExpr))
Value))
return true;
if (!Sym) {
@ -5839,17 +5840,13 @@ static bool isSymbolUsedInExpression(const MCSymbol *Sym, const MCExpr *Value) {
bool parseAssignmentExpression(StringRef Name, bool allow_redef,
MCAsmParser &Parser, MCSymbol *&Sym,
const MCExpr *&Value, bool AllowExtendedExpr) {
const MCExpr *&Value) {
// FIXME: Use better location, we should use proper tokens.
SMLoc EqualLoc = Parser.getTok().getLoc();
SMLoc EndLoc;
if (AllowExtendedExpr) {
if (Parser.getTargetParser().parseAssignmentExpression(Value, EndLoc)) {
return Parser.TokError("missing expression");
}
} else if (Parser.parseExpression(Value, EndLoc))
return Parser.TokError("missing expression");
if (Parser.parseExpression(Value))
return Parser.TokError("missing expression");
// Note: we don't count b as used in "a = b". This is to allow
// a = b

14
lib/Target/X86/AsmParser/X86AsmParser.cpp
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@ -955,7 +955,7 @@ public:
void SetFrameRegister(unsigned RegNo) override;
bool parseAssignmentExpression(const MCExpr *&Res, SMLoc &EndLoc) override;
bool parsePrimaryExpr(const MCExpr *&Res, SMLoc &EndLoc) override;
bool ParseInstruction(ParseInstructionInfo &Info, StringRef Name,
SMLoc NameLoc, OperandVector &Operands) override;
@ -2260,15 +2260,17 @@ std::unique_ptr<X86Operand> X86AsmParser::ParseMemOperand(unsigned SegReg,
return X86Operand::CreateMem(getPointerWidth(), Disp, MemStart, MemEnd);
}
// Parse either a standard expression or a register.
bool X86AsmParser::parseAssignmentExpression(const MCExpr *&Res,
SMLoc &EndLoc) {
// Parse either a standard primary expression or a register.
bool X86AsmParser::parsePrimaryExpr(const MCExpr *&Res, SMLoc &EndLoc) {
MCAsmParser &Parser = getParser();
if (Parser.parseExpression(Res, EndLoc)) {
if (Parser.parsePrimaryExpr(Res, EndLoc)) {
SMLoc StartLoc = Parser.getTok().getLoc();
// Normal Expression parse fails, check if it could be a register.
unsigned RegNo;
if (Parser.getTargetParser().ParseRegister(RegNo, StartLoc, EndLoc))
bool TryRegParse =
getTok().is(AsmToken::Percent) ||
(isParsingIntelSyntax() && getTok().is(AsmToken::Identifier));
if (!TryRegParse || ParseRegister(RegNo, StartLoc, EndLoc))
return true;
// Clear previous parse error and return correct expression.
Parser.clearPendingErrors();

7
lib/Target/X86/MCTargetDesc/X86MCExpr.h
View File

@ -48,7 +48,7 @@ public:
/// @}
void printImpl(raw_ostream &OS, const MCAsmInfo *MAI) const override {
if (MAI->getAssemblerDialect() == 0)
if (!MAI || MAI->getAssemblerDialect() == 0)
OS << '%';
OS << X86ATTInstPrinter::getRegisterName(RegNo);
}
@ -59,6 +59,11 @@ public:
}
// Register values should be inlined as they are not valid .set expressions.
bool inlineAssignedExpr() const override { return true; }
bool isEqualTo(const MCExpr *X) const override {
if (auto *E = dyn_cast<X86MCExpr>(X))
return getRegNo() == E->getRegNo();
return false;
}
void visitUsedExpr(MCStreamer &Streamer) const override{};
MCFragment *findAssociatedFragment() const override { return nullptr; }

18
test/MC/X86/pr37425.s
View File

@ -1,5 +1,4 @@
// RUN: llvm-mc -triple x86_64-unknown-unknown -defsym=ERR=0 %s -o - | FileCheck %s
// RUN: not llvm-mc -triple x86_64-unknown-unknown -defsym=ERR=1 %s -o - 2>&1 | FileCheck --check-prefix=ERR %s
// RUN: llvm-mc -triple x86_64-unknown-unknown %s -o - | FileCheck %s
// CHECK-NOT: .set var_xdata
var_xdata = %rcx
@ -7,10 +6,15 @@ var_xdata = %rcx
// CHECK: xorq %rcx, %rcx
xorq var_xdata, var_xdata
.if (ERR==1)
// ERR: [[@LINE+2]]:15: error: unknown token in expression in '.set' directive
// ERR: [[@LINE+1]]:15: error: missing expression in '.set' directive
.set err_var, %rcx
.endif
// CHECK: .data
// CHECK-NEXT: .byte 1
.data
.if var_xdata == %rax
.byte 0
.elseif var_xdata == %rcx
.byte 1
.else
.byte 2
.endif