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enhance vmcore to know that udiv's can be exact, and add a trivial 

instcombine xform to exercise this.

Nothing forms exact udivs yet though.  This is progress on PR8862

llvm-svn: 124992
This commit is contained in:
Chris Lattner 2011-02-06 21:44:57 +00:00
parent b54605b8e2
commit 35315d065b
14 changed files with 110 additions and 32 deletions
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8
llvm/docs/LangRef.html
View File

@ -3441,7 +3441,8 @@ Instruction</a> </div>
<h5>Syntax:</h5>
<pre>
&lt;result&gt; = udiv &lt;ty&gt; &lt;op1&gt;, &lt;op2&gt; <i>; yields {ty}:result</i>
&lt;result&gt; = udiv &lt;ty&gt; &lt;op1&gt;, &lt;op2&gt; <i>; yields {ty}:result</i>
&lt;result&gt; = udiv exact &lt;ty&gt; &lt;op1&gt;, &lt;op2&gt; <i>; yields {ty}:result</i>
</pre>
<h5>Overview:</h5>
@ -3460,6 +3461,11 @@ Instruction</a> </div>
<p>Division by zero leads to undefined behavior.</p>
<p>If the <tt>exact</tt> keyword is present, the result value of the
<tt>udiv</tt> is a <a href="#trapvalues">trap value</a> if %op1 is not a
multiple of %op2 (as such, "((a udiv exact b) mul b) == a").</p>
<h5>Example:</h5>
<pre>
&lt;result&gt; = udiv i32 4, %var <i>; yields {i32}:result = 4 / %var</i>

8
llvm/include/llvm/Bitcode/LLVMBitCodes.h
View File

@ -199,10 +199,10 @@ namespace bitc {
OBO_NO_SIGNED_WRAP = 1
};
/// SDivOperatorOptionalFlags - Flags for serializing SDivOperator's
/// SubclassOptionalData contents.
enum SDivOperatorOptionalFlags {
SDIV_EXACT = 0
/// PossiblyExactOperatorOptionalFlags - Flags for serializing
/// PossiblyExactOperator's SubclassOptionalData contents.
enum PossiblyExactOperatorOptionalFlags {
PEO_EXACT = 0
};
// The function body block (FUNCTION_BLOCK_ID) describes function bodies. It

1
llvm/include/llvm/Constants.h
View File

@ -725,6 +725,7 @@ public:
static Constant *getNSWMul(Constant *C1, Constant *C2);
static Constant *getNUWMul(Constant *C1, Constant *C2);
static Constant *getExactSDiv(Constant *C1, Constant *C2);
static Constant *getExactUDiv(Constant *C1, Constant *C2);
/// Transparently provide more efficient getOperand methods.
DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Constant);

2
llvm/include/llvm/InstrTypes.h
View File

@ -341,7 +341,7 @@ public:
BO->setIsExact(true);
return BO;
}
/// Helper functions to construct and inspect unary operations (NEG and NOT)
/// via binary operators SUB and XOR:
///

53
llvm/include/llvm/Operator.h
View File

@ -173,30 +173,47 @@ public:
}
};
/// SDivOperator - An Operator with opcode Instruction::SDiv.
///
class SDivOperator : public Operator {
/// PossiblyExactOperator - A udiv or sdiv instruction, which can be marked as
/// "exact", indicating that no bits are destroyed.
class PossiblyExactOperator : public Operator {
public:
enum {
IsExact = (1 << 0)
};
private:
~SDivOperator(); // do not implement
friend class BinaryOperator;
friend class ConstantExpr;
void setIsExact(bool B) {
SubclassOptionalData = (SubclassOptionalData & ~IsExact) | (B * IsExact);
}
private:
~PossiblyExactOperator(); // do not implement
public:
/// isExact - Test whether this division is known to be exact, with
/// zero remainder.
bool isExact() const {
return SubclassOptionalData & IsExact;
}
static inline bool classof(const ConstantExpr *CE) {
return CE->getOpcode() == Instruction::SDiv ||
CE->getOpcode() == Instruction::UDiv;
}
static inline bool classof(const Instruction *I) {
return I->getOpcode() == Instruction::SDiv ||
I->getOpcode() == Instruction::UDiv;
}
static inline bool classof(const Value *V) {
return (isa<Instruction>(V) && classof(cast<Instruction>(V))) ||
(isa<ConstantExpr>(V) && classof(cast<ConstantExpr>(V)));
}
};
/// SDivOperator - An Operator with opcode Instruction::SDiv.
///
class SDivOperator : public PossiblyExactOperator {
public:
// Methods for support type inquiry through isa, cast, and dyn_cast:
static inline bool classof(const SDivOperator *) { return true; }
static inline bool classof(const ConstantExpr *CE) {
@ -211,6 +228,24 @@ public:
}
};
/// UDivOperator - An Operator with opcode Instruction::SDiv.
///
class UDivOperator : public PossiblyExactOperator {
public:
// Methods for support type inquiry through isa, cast, and dyn_cast:
static inline bool classof(const UDivOperator *) { return true; }
static inline bool classof(const ConstantExpr *CE) {
return CE->getOpcode() == Instruction::UDiv;
}
static inline bool classof(const Instruction *I) {
return I->getOpcode() == Instruction::UDiv;
}
static inline bool classof(const Value *V) {
return (isa<Instruction>(V) && classof(cast<Instruction>(V))) ||
(isa<ConstantExpr>(V) && classof(cast<ConstantExpr>(V)));
}
};
class GEPOperator : public Operator {
enum {
IsInBounds = (1 << 0)

8
llvm/lib/AsmParser/LLParser.cpp
View File

@ -2304,7 +2304,7 @@ bool LLParser::ParseValID(ValID &ID, PerFunctionState *PFS) {
if (EatIfPresent(lltok::kw_nuw))
NUW = true;
}
} else if (Opc == Instruction::SDiv) {
} else if (Opc == Instruction::SDiv || Opc == Instruction::UDiv) {
if (EatIfPresent(lltok::kw_exact))
Exact = true;
}
@ -2347,7 +2347,7 @@ bool LLParser::ParseValID(ValID &ID, PerFunctionState *PFS) {
unsigned Flags = 0;
if (NUW) Flags |= OverflowingBinaryOperator::NoUnsignedWrap;
if (NSW) Flags |= OverflowingBinaryOperator::NoSignedWrap;
if (Exact) Flags |= SDivOperator::IsExact;
if (Exact) Flags |= PossiblyExactOperator::IsExact;
Constant *C = ConstantExpr::get(Opc, Val0, Val1, Flags);
ID.ConstantVal = C;
ID.Kind = ValID::t_Constant;
@ -3032,7 +3032,8 @@ int LLParser::ParseInstruction(Instruction *&Inst, BasicBlock *BB,
case lltok::kw_fsub:
case lltok::kw_fmul: return ParseArithmetic(Inst, PFS, KeywordVal, 2);
case lltok::kw_sdiv: {
case lltok::kw_sdiv:
case lltok::kw_udiv: {
bool Exact = false;
if (EatIfPresent(lltok::kw_exact))
Exact = true;
@ -3043,7 +3044,6 @@ int LLParser::ParseInstruction(Instruction *&Inst, BasicBlock *BB,
return Result;
}
case lltok::kw_udiv:
case lltok::kw_urem:
case lltok::kw_srem: return ParseArithmetic(Inst, PFS, KeywordVal, 1);
case lltok::kw_fdiv:

10
llvm/lib/Bitcode/Reader/BitcodeReader.cpp
View File

@ -1090,8 +1090,9 @@ bool BitcodeReader::ParseConstants() {
Flags |= OverflowingBinaryOperator::NoSignedWrap;
if (Record[3] & (1 << bitc::OBO_NO_UNSIGNED_WRAP))
Flags |= OverflowingBinaryOperator::NoUnsignedWrap;
} else if (Opc == Instruction::SDiv) {
if (Record[3] & (1 << bitc::SDIV_EXACT))
} else if (Opc == Instruction::SDiv ||
Opc == Instruction::UDiv) {
if (Record[3] & (1 << bitc::PEO_EXACT))
Flags |= SDivOperator::IsExact;
}
}
@ -1905,8 +1906,9 @@ bool BitcodeReader::ParseFunctionBody(Function *F) {
cast<BinaryOperator>(I)->setHasNoSignedWrap(true);
if (Record[OpNum] & (1 << bitc::OBO_NO_UNSIGNED_WRAP))
cast<BinaryOperator>(I)->setHasNoUnsignedWrap(true);
} else if (Opc == Instruction::SDiv) {
if (Record[OpNum] & (1 << bitc::SDIV_EXACT))
} else if (Opc == Instruction::SDiv ||
Opc == Instruction::UDiv) {
if (Record[OpNum] & (1 << bitc::PEO_EXACT))
cast<BinaryOperator>(I)->setIsExact(true);
}
}

7
llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
View File

@ -470,9 +470,10 @@ static uint64_t GetOptimizationFlags(const Value *V) {
Flags |= 1 << bitc::OBO_NO_SIGNED_WRAP;
if (OBO->hasNoUnsignedWrap())
Flags |= 1 << bitc::OBO_NO_UNSIGNED_WRAP;
} else if (const SDivOperator *Div = dyn_cast<SDivOperator>(V)) {
if (Div->isExact())
Flags |= 1 << bitc::SDIV_EXACT;
} else if (const PossiblyExactOperator *PEO =
dyn_cast<PossiblyExactOperator>(V)) {
if (PEO->isExact())
Flags |= 1 << bitc::PEO_EXACT;
}
return Flags;

4
llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
View File

@ -135,8 +135,8 @@ Instruction *InstCombiner::visitMul(BinaryOperator &I) {
BO->getOpcode() == Instruction::SDiv)) {
Value *Op0BO = BO->getOperand(0), *Op1BO = BO->getOperand(1);
// If the division is exact, X % Y is zero.
if (SDivOperator *SDiv = dyn_cast<SDivOperator>(BO))
// If the division is exact, X % Y is zero, so we end up with X or -X.
if (PossiblyExactOperator *SDiv = dyn_cast<PossiblyExactOperator>(BO))
if (SDiv->isExact()) {
if (Op1BO == Op1C)
return ReplaceInstUsesWith(I, Op0BO);

3
llvm/lib/VMCore/AsmWriter.cpp
View File

@ -831,7 +831,8 @@ static void WriteOptimizationInfo(raw_ostream &Out, const User *U) {
Out << " nuw";
if (OBO->hasNoSignedWrap())
Out << " nsw";
} else if (const SDivOperator *Div = dyn_cast<SDivOperator>(U)) {
} else if (const PossiblyExactOperator *Div =
dyn_cast<PossiblyExactOperator>(U)) {
if (Div->isExact())
Out << " exact";
} else if (const GEPOperator *GEP = dyn_cast<GEPOperator>(U)) {

7
llvm/lib/VMCore/Constants.cpp
View File

@ -683,7 +683,12 @@ Constant* ConstantExpr::getNUWMul(Constant* C1, Constant* C2) {
Constant* ConstantExpr::getExactSDiv(Constant* C1, Constant* C2) {
return getTy(C1->getType(), Instruction::SDiv, C1, C2,
SDivOperator::IsExact);
PossiblyExactOperator::IsExact);
}
Constant* ConstantExpr::getExactUDiv(Constant* C1, Constant* C2) {
return getTy(C1->getType(), Instruction::UDiv, C1, C2,
PossiblyExactOperator::IsExact);
}
// Utility function for determining if a ConstantExpr is a CastOp or not. This

4
llvm/lib/VMCore/Instructions.cpp
View File

@ -1822,7 +1822,7 @@ void BinaryOperator::setHasNoSignedWrap(bool b) {
}
void BinaryOperator::setIsExact(bool b) {
cast<SDivOperator>(this)->setIsExact(b);
cast<PossiblyExactOperator>(this)->setIsExact(b);
}
bool BinaryOperator::hasNoUnsignedWrap() const {
@ -1834,7 +1834,7 @@ bool BinaryOperator::hasNoSignedWrap() const {
}
bool BinaryOperator::isExact() const {
return cast<SDivOperator>(this)->isExact();
return cast<PossiblyExactOperator>(this)->isExact();
}
//===----------------------------------------------------------------------===//

19
llvm/test/Assembler/flags.ll
View File

@ -104,6 +104,19 @@ define i64 @sdiv_plain(i64 %x, i64 %y) {
ret i64 %z
}
define i64 @udiv_exact(i64 %x, i64 %y) {
; CHECK: %z = udiv exact i64 %x, %y
%z = udiv exact i64 %x, %y
ret i64 %z
}
define i64 @udiv_plain(i64 %x, i64 %y) {
; CHECK: %z = udiv i64 %x, %y
%z = udiv i64 %x, %y
ret i64 %z
}
define i64* @gep_nw(i64* %p, i64 %x) {
; CHECK: %z = getelementptr inbounds i64* %p, i64 %x
%z = getelementptr inbounds i64* %p, i64 %x
@ -136,6 +149,11 @@ define i64 @sdiv_exact_ce() {
ret i64 sdiv exact (i64 ptrtoint (i64* @addr to i64), i64 91)
}
define i64 @udiv_exact_ce() {
; CHECK: ret i64 udiv exact (i64 ptrtoint (i64* @addr to i64), i64 91)
ret i64 udiv exact (i64 ptrtoint (i64* @addr to i64), i64 91)
}
define i64* @gep_nw_ce() {
; CHECK: ret i64* getelementptr inbounds (i64* @addr, i64 171)
ret i64* getelementptr inbounds (i64* @addr, i64 171)
@ -210,3 +228,4 @@ define i64 @mul_unsigned_ce() {
; CHECK: ret i64 mul nuw (i64 ptrtoint (i64* @addr to i64), i64 91)
ret i64 mul nuw (i64 ptrtoint (i64* @addr to i64), i64 91)
}

8
llvm/test/Transforms/InstCombine/exact-sdiv.ll → llvm/test/Transforms/InstCombine/exact.ll
View File

@ -50,3 +50,11 @@ define i32 @b1(i32 %x) {
%z = mul i32 %y, -3
ret i32 %z
}
; CHECK: i32 @b2
; CHECK: ret i32 %x
define i32 @b2(i32 %x, i32 %w) {
%y = udiv exact i32 %x, %w
%z = mul i32 %y, %w
ret i32 %z
}