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Add support for fast-math flags to the FCmp instruction.

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FCmp behaves a lot like a floating-point binary operator in many ways,
and can benefit from fast-math information. Flags such as nsz and nnan
can affect if this fcmp (in combination with a select) can be treated
as a fminnum/fmaxnum operation.

This adds backwards-compatible bitcode support, IR parsing and writing,
LangRef changes and IRBuilder changes. I'll need to audit InstSimplify
and InstCombine in a followup to find places where flags should be
copied.

llvm-svn: 241901
This commit is contained in:
James Molloy 2015-07-10 12:52:00 +00:00
parent 11ffb4756d
commit 4008b8e3dc
8 changed files with 149 additions and 54 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
docs/LangRef.rst
View File

@ -1837,8 +1837,8 @@ Fast-Math Flags
LLVM IR floating-point binary ops (:ref:`fadd <i_fadd>`,
:ref:`fsub <i_fsub>`, :ref:`fmul <i_fmul>`, :ref:`fdiv <i_fdiv>`,
:ref:`frem <i_frem>`) have the following flags that can be set to enable
otherwise unsafe floating point operations
:ref:`frem <i_frem>`, :ref:`fcmp <i_fcmp>`) have the following flags that can
be set to enable otherwise unsafe floating point operations
``nnan``
No NaNs - Allow optimizations to assume the arguments and result are not
@ -7573,7 +7573,7 @@ Syntax:
::
<result> = fcmp <cond> <ty> <op1>, <op2> ; yields i1 or <N x i1>:result
<result> = fcmp [fast-math flags]* <cond> <ty> <op1>, <op2> ; yields i1 or <N x i1>:result
Overview:
"""""""""
@ -7656,6 +7656,15 @@ always yields an :ref:`i1 <t_integer>` result, as follows:
#. ``uno``: yields ``true`` if either operand is a QNAN.
#. ``true``: always yields ``true``, regardless of operands.
The ``fcmp`` instruction can also optionally take any number of
:ref:`fast-math flags <fastmath>`, which are optimization hints to enable
otherwise unsafe floating point optimizations.
Any set of fast-math flags are legal on an ``fcmp`` instruction, but the
only flags that have any effect on its semantics are those that allow
assumptions to be made about the values of input arguments; namely
``nnan``, ``ninf``, and ``nsz``. See :ref:`fastmath` for more information.
Example:
""""""""

75
include/llvm/IR/IRBuilder.h
View File

@ -1382,47 +1382,61 @@ public:
return CreateICmp(ICmpInst::ICMP_SLE, LHS, RHS, Name);
}
Value *CreateFCmpOEQ(Value *LHS, Value *RHS, const Twine &Name = "") {
return CreateFCmp(FCmpInst::FCMP_OEQ, LHS, RHS, Name);
Value *CreateFCmpOEQ(Value *LHS, Value *RHS, const Twine &Name = "",
MDNode *FPMathTag = nullptr) {
return CreateFCmp(FCmpInst::FCMP_OEQ, LHS, RHS, Name, FPMathTag);
}
Value *CreateFCmpOGT(Value *LHS, Value *RHS, const Twine &Name = "") {
return CreateFCmp(FCmpInst::FCMP_OGT, LHS, RHS, Name);
Value *CreateFCmpOGT(Value *LHS, Value *RHS, const Twine &Name = "",
MDNode *FPMathTag = nullptr) {
return CreateFCmp(FCmpInst::FCMP_OGT, LHS, RHS, Name, FPMathTag);
}
Value *CreateFCmpOGE(Value *LHS, Value *RHS, const Twine &Name = "") {
return CreateFCmp(FCmpInst::FCMP_OGE, LHS, RHS, Name);
Value *CreateFCmpOGE(Value *LHS, Value *RHS, const Twine &Name = "",
MDNode *FPMathTag = nullptr) {
return CreateFCmp(FCmpInst::FCMP_OGE, LHS, RHS, Name, FPMathTag);
}
Value *CreateFCmpOLT(Value *LHS, Value *RHS, const Twine &Name = "") {
return CreateFCmp(FCmpInst::FCMP_OLT, LHS, RHS, Name);
Value *CreateFCmpOLT(Value *LHS, Value *RHS, const Twine &Name = "",
MDNode *FPMathTag = nullptr) {
return CreateFCmp(FCmpInst::FCMP_OLT, LHS, RHS, Name, FPMathTag);
}
Value *CreateFCmpOLE(Value *LHS, Value *RHS, const Twine &Name = "") {
return CreateFCmp(FCmpInst::FCMP_OLE, LHS, RHS, Name);
Value *CreateFCmpOLE(Value *LHS, Value *RHS, const Twine &Name = "",
MDNode *FPMathTag = nullptr) {
return CreateFCmp(FCmpInst::FCMP_OLE, LHS, RHS, Name, FPMathTag);
}
Value *CreateFCmpONE(Value *LHS, Value *RHS, const Twine &Name = "") {
return CreateFCmp(FCmpInst::FCMP_ONE, LHS, RHS, Name);
Value *CreateFCmpONE(Value *LHS, Value *RHS, const Twine &Name = "",
MDNode *FPMathTag = nullptr) {
return CreateFCmp(FCmpInst::FCMP_ONE, LHS, RHS, Name, FPMathTag);
}
Value *CreateFCmpORD(Value *LHS, Value *RHS, const Twine &Name = "") {
return CreateFCmp(FCmpInst::FCMP_ORD, LHS, RHS, Name);
Value *CreateFCmpORD(Value *LHS, Value *RHS, const Twine &Name = "",
MDNode *FPMathTag = nullptr) {
return CreateFCmp(FCmpInst::FCMP_ORD, LHS, RHS, Name, FPMathTag);
}
Value *CreateFCmpUNO(Value *LHS, Value *RHS, const Twine &Name = "") {
return CreateFCmp(FCmpInst::FCMP_UNO, LHS, RHS, Name);
Value *CreateFCmpUNO(Value *LHS, Value *RHS, const Twine &Name = "",
MDNode *FPMathTag = nullptr) {
return CreateFCmp(FCmpInst::FCMP_UNO, LHS, RHS, Name, FPMathTag);
}
Value *CreateFCmpUEQ(Value *LHS, Value *RHS, const Twine &Name = "") {
return CreateFCmp(FCmpInst::FCMP_UEQ, LHS, RHS, Name);
Value *CreateFCmpUEQ(Value *LHS, Value *RHS, const Twine &Name = "",
MDNode *FPMathTag = nullptr) {
return CreateFCmp(FCmpInst::FCMP_UEQ, LHS, RHS, Name, FPMathTag);
}
Value *CreateFCmpUGT(Value *LHS, Value *RHS, const Twine &Name = "") {
return CreateFCmp(FCmpInst::FCMP_UGT, LHS, RHS, Name);
Value *CreateFCmpUGT(Value *LHS, Value *RHS, const Twine &Name = "",
MDNode *FPMathTag = nullptr) {
return CreateFCmp(FCmpInst::FCMP_UGT, LHS, RHS, Name, FPMathTag);
}
Value *CreateFCmpUGE(Value *LHS, Value *RHS, const Twine &Name = "") {
return CreateFCmp(FCmpInst::FCMP_UGE, LHS, RHS, Name);
Value *CreateFCmpUGE(Value *LHS, Value *RHS, const Twine &Name = "",
MDNode *FPMathTag = nullptr) {
return CreateFCmp(FCmpInst::FCMP_UGE, LHS, RHS, Name, FPMathTag);
}
Value *CreateFCmpULT(Value *LHS, Value *RHS, const Twine &Name = "") {
return CreateFCmp(FCmpInst::FCMP_ULT, LHS, RHS, Name);
Value *CreateFCmpULT(Value *LHS, Value *RHS, const Twine &Name = "",
MDNode *FPMathTag = nullptr) {
return CreateFCmp(FCmpInst::FCMP_ULT, LHS, RHS, Name, FPMathTag);
}
Value *CreateFCmpULE(Value *LHS, Value *RHS, const Twine &Name = "") {
return CreateFCmp(FCmpInst::FCMP_ULE, LHS, RHS, Name);
Value *CreateFCmpULE(Value *LHS, Value *RHS, const Twine &Name = "",
MDNode *FPMathTag = nullptr) {
return CreateFCmp(FCmpInst::FCMP_ULE, LHS, RHS, Name, FPMathTag);
}
Value *CreateFCmpUNE(Value *LHS, Value *RHS, const Twine &Name = "") {
return CreateFCmp(FCmpInst::FCMP_UNE, LHS, RHS, Name);
Value *CreateFCmpUNE(Value *LHS, Value *RHS, const Twine &Name = "",
MDNode *FPMathTag = nullptr) {
return CreateFCmp(FCmpInst::FCMP_UNE, LHS, RHS, Name, FPMathTag);
}
Value *CreateICmp(CmpInst::Predicate P, Value *LHS, Value *RHS,
@ -1433,11 +1447,12 @@ public:
return Insert(new ICmpInst(P, LHS, RHS), Name);
}
Value *CreateFCmp(CmpInst::Predicate P, Value *LHS, Value *RHS,
const Twine &Name = "") {
const Twine &Name = "", MDNode *FPMathTag = nullptr) {
if (Constant *LC = dyn_cast<Constant>(LHS))
if (Constant *RC = dyn_cast<Constant>(RHS))
return Insert(Folder.CreateFCmp(P, LC, RC), Name);
return Insert(new FCmpInst(P, LHS, RHS), Name);
return Insert(AddFPMathAttributes(new FCmpInst(P, LHS, RHS),
FPMathTag, FMF), Name);
}
//===--------------------------------------------------------------------===//

3
include/llvm/IR/Operator.h
View File

@ -305,7 +305,8 @@ public:
float getFPAccuracy() const;
static inline bool classof(const Instruction *I) {
return I->getType()->isFPOrFPVectorTy();
return I->getType()->isFPOrFPVectorTy() ||
I->getOpcode() == Instruction::FCmp;
}
static inline bool classof(const Value *V) {
return isa<Instruction>(V) && classof(cast<Instruction>(V));

13
lib/AsmParser/LLParser.cpp
View File

@ -4534,8 +4534,17 @@ int LLParser::ParseInstruction(Instruction *&Inst, BasicBlock *BB,
case lltok::kw_and:
case lltok::kw_or:
case lltok::kw_xor: return ParseLogical(Inst, PFS, KeywordVal);
case lltok::kw_icmp:
case lltok::kw_fcmp: return ParseCompare(Inst, PFS, KeywordVal);
case lltok::kw_icmp: return ParseCompare(Inst, PFS, KeywordVal);
case lltok::kw_fcmp: {
FastMathFlags FMF = EatFastMathFlagsIfPresent();
int Res = ParseCompare(Inst, PFS, KeywordVal);
if (Res != 0)
return Res;
if (FMF.any())
Inst->setFastMathFlags(FMF);
return 0;
}
// Casts.
case lltok::kw_trunc:
case lltok::kw_zext:

46
lib/Bitcode/Reader/BitcodeReader.cpp
View File

@ -697,6 +697,21 @@ static Comdat::SelectionKind getDecodedComdatSelectionKind(unsigned Val) {
}
}
static FastMathFlags getDecodedFastMathFlags(unsigned Val) {
FastMathFlags FMF;
if (0 != (Val & FastMathFlags::UnsafeAlgebra))
FMF.setUnsafeAlgebra();
if (0 != (Val & FastMathFlags::NoNaNs))
FMF.setNoNaNs();
if (0 != (Val & FastMathFlags::NoInfs))
FMF.setNoInfs();
if (0 != (Val & FastMathFlags::NoSignedZeros))
FMF.setNoSignedZeros();
if (0 != (Val & FastMathFlags::AllowReciprocal))
FMF.setAllowReciprocal();
return FMF;
}
static void upgradeDLLImportExportLinkage(llvm::GlobalValue *GV, unsigned Val) {
switch (Val) {
case 5: GV->setDLLStorageClass(GlobalValue::DLLImportStorageClass); break;
@ -3472,17 +3487,7 @@ std::error_code BitcodeReader::parseFunctionBody(Function *F) {
if (Record[OpNum] & (1 << bitc::PEO_EXACT))
cast<BinaryOperator>(I)->setIsExact(true);
} else if (isa<FPMathOperator>(I)) {
FastMathFlags FMF;
if (0 != (Record[OpNum] & FastMathFlags::UnsafeAlgebra))
FMF.setUnsafeAlgebra();
if (0 != (Record[OpNum] & FastMathFlags::NoNaNs))
FMF.setNoNaNs();
if (0 != (Record[OpNum] & FastMathFlags::NoInfs))
FMF.setNoInfs();
if (0 != (Record[OpNum] & FastMathFlags::NoSignedZeros))
FMF.setNoSignedZeros();
if (0 != (Record[OpNum] & FastMathFlags::AllowReciprocal))
FMF.setAllowReciprocal();
FastMathFlags FMF = getDecodedFastMathFlags(Record[OpNum]);
if (FMF.any())
I->setFastMathFlags(FMF);
}
@ -3739,14 +3744,25 @@ std::error_code BitcodeReader::parseFunctionBody(Function *F) {
unsigned OpNum = 0;
Value *LHS, *RHS;
if (getValueTypePair(Record, OpNum, NextValueNo, LHS) ||
popValue(Record, OpNum, NextValueNo, LHS->getType(), RHS) ||
OpNum+1 != Record.size())
popValue(Record, OpNum, NextValueNo, LHS->getType(), RHS))
return error("Invalid record");
unsigned PredVal = Record[OpNum];
bool IsFP = LHS->getType()->isFPOrFPVectorTy();
FastMathFlags FMF;
if (IsFP && Record.size() > OpNum+1)
FMF = getDecodedFastMathFlags(Record[++OpNum]);
if (OpNum+1 != Record.size())
return error("Invalid record");
if (LHS->getType()->isFPOrFPVectorTy())
I = new FCmpInst((FCmpInst::Predicate)Record[OpNum], LHS, RHS);
I = new FCmpInst((FCmpInst::Predicate)PredVal, LHS, RHS);
else
I = new ICmpInst((ICmpInst::Predicate)Record[OpNum], LHS, RHS);
I = new ICmpInst((ICmpInst::Predicate)PredVal, LHS, RHS);
if (FMF.any())
I->setFastMathFlags(FMF);
InstructionList.push_back(I);
break;
}

6
lib/Bitcode/Writer/BitcodeWriter.cpp
View File

@ -1759,13 +1759,17 @@ static void WriteInstruction(const Instruction &I, unsigned InstID,
pushValue(I.getOperand(2), InstID, Vals, VE);
break;
case Instruction::ICmp:
case Instruction::FCmp:
case Instruction::FCmp: {
// compare returning Int1Ty or vector of Int1Ty
Code = bitc::FUNC_CODE_INST_CMP2;
PushValueAndType(I.getOperand(0), InstID, Vals, VE);
pushValue(I.getOperand(1), InstID, Vals, VE);
Vals.push_back(cast<CmpInst>(I).getPredicate());
uint64_t Flags = GetOptimizationFlags(&I);
if (Flags != 0)
Vals.push_back(Flags);
break;
}
case Instruction::Ret:
{

23
test/Bitcode/fcmp-fast.ll Normal file
View File

@ -0,0 +1,23 @@
; RUN: llvm-as < %s | llvm-dis > %t0
; RUN: opt -S < %s > %t1
; RUN: diff %t0 %t1
; RUN: FileCheck < %t1 %s
; Make sure flags on fcmp instructions are serialized/deserialized properly.
define i1 @foo(float %a, float %b, double %c, double %d) {
; CHECK: %plain = fcmp ueq float %a, %b
%plain = fcmp ueq float %a, %b
; CHECK: %fast = fcmp fast olt float %a, %b
%fast = fcmp fast olt float %a, %b
; CHECK: %nsz = fcmp nsz uge float %a, %b
%nsz = fcmp nsz uge float %a, %b
; CHECK: %nnan = fcmp nnan nsz oge double %c, %d
%nnan = fcmp nnan nsz oge double %c, %d
%dce1 = or i1 %plain, %fast
%dce2 = or i1 %dce1, %nsz
%dce3 = or i1 %dce2, %nnan
ret i1 %dce3
}

22
unittests/IR/IRBuilderTest.cpp
View File

@ -130,8 +130,8 @@ TEST_F(IRBuilderTest, GetIntTy) {
TEST_F(IRBuilderTest, FastMathFlags) {
IRBuilder<> Builder(BB);
Value *F;
Instruction *FDiv, *FAdd;
Value *F, *FC;
Instruction *FDiv, *FAdd, *FCmp;
F = Builder.CreateLoad(GV);
F = Builder.CreateFAdd(F, F);
@ -190,6 +190,24 @@ TEST_F(IRBuilderTest, FastMathFlags) {
Builder.clearFastMathFlags();
FC = Builder.CreateFCmpOEQ(F, F);
ASSERT_TRUE(isa<Instruction>(FC));
FCmp = cast<Instruction>(FC);
EXPECT_FALSE(FCmp->hasAllowReciprocal());
FMF.clear();
FMF.setAllowReciprocal();
Builder.SetFastMathFlags(FMF);
FC = Builder.CreateFCmpOEQ(F, F);
EXPECT_TRUE(Builder.getFastMathFlags().any());
EXPECT_TRUE(Builder.getFastMathFlags().AllowReciprocal);
ASSERT_TRUE(isa<Instruction>(FC));
FCmp = cast<Instruction>(FC);
EXPECT_TRUE(FCmp->hasAllowReciprocal());
Builder.clearFastMathFlags();
// To test a copy, make sure that a '0' and a '1' change state.
F = Builder.CreateFDiv(F, F);
ASSERT_TRUE(isa<Instruction>(F));