[IR] allow fast-math-flags on phi of FP values (2nd try)
The changes here are based on the corresponding diffs for allowing FMF on 'select':
D61917 <https://reviews.llvm.org/D61917>
As discussed there, we want to have fast-math-flags be a property of an FP value
because the alternative (having them on things like fcmp) leads to logical
inconsistency such as:
https://bugs.llvm.org/show_bug.cgi?id=38086
The earlier patch for select made almost no practical difference because most
unoptimized conditional code begins life as a phi (based on what I see in clang).
Similarly, I don't expect this patch to do much on its own either because
SimplifyCFG promptly drops the flags when converting to select on a minimal
example like:
https://bugs.llvm.org/show_bug.cgi?id=39535
But once we have this plumbing in place, we should be able to wire up the FMF
propagation and start solving cases like that.
The change to RecurrenceDescriptor::AddReductionVar() is required to prevent a
regression in a LoopVectorize test. We are intersecting the FMF of any
FPMathOperator there, so if a phi is not properly annotated, new math
instructions may not be either. Once we fix the propagation in SimplifyCFG, it
may be safe to remove that hack.
Differential Revision: https://reviews.llvm.org/D67564
llvm-svn: 372878
diff --git a/llvm/lib/Analysis/IVDescriptors.cpp b/llvm/lib/Analysis/IVDescriptors.cpp
index ce285f8..6fb6001 100644
--- a/llvm/lib/Analysis/IVDescriptors.cpp
+++ b/llvm/lib/Analysis/IVDescriptors.cpp
@@ -300,7 +300,8 @@
ReduxDesc = isRecurrenceInstr(Cur, Kind, ReduxDesc, HasFunNoNaNAttr);
if (!ReduxDesc.isRecurrence())
return false;
- if (isa<FPMathOperator>(ReduxDesc.getPatternInst()))
+ // FIXME: FMF is allowed on phi, but propagation is not handled correctly.
+ if (isa<FPMathOperator>(ReduxDesc.getPatternInst()) && !IsAPhi)
FMF &= ReduxDesc.getPatternInst()->getFastMathFlags();
}
diff --git a/llvm/lib/AsmParser/LLParser.cpp b/llvm/lib/AsmParser/LLParser.cpp
index eb66a7c..5ea0b7d 100644
--- a/llvm/lib/AsmParser/LLParser.cpp
+++ b/llvm/lib/AsmParser/LLParser.cpp
@@ -5802,7 +5802,19 @@
case lltok::kw_extractelement: return ParseExtractElement(Inst, PFS);
case lltok::kw_insertelement: return ParseInsertElement(Inst, PFS);
case lltok::kw_shufflevector: return ParseShuffleVector(Inst, PFS);
- case lltok::kw_phi: return ParsePHI(Inst, PFS);
+ case lltok::kw_phi: {
+ FastMathFlags FMF = EatFastMathFlagsIfPresent();
+ int Res = ParsePHI(Inst, PFS);
+ if (Res != 0)
+ return Res;
+ if (FMF.any()) {
+ if (!Inst->getType()->isFPOrFPVectorTy())
+ return Error(Loc, "fast-math-flags specified for phi without "
+ "floating-point scalar or vector return type");
+ Inst->setFastMathFlags(FMF);
+ }
+ return 0;
+ }
case lltok::kw_landingpad: return ParseLandingPad(Inst, PFS);
// Call.
case lltok::kw_call: return ParseCall(Inst, PFS, CallInst::TCK_None);
diff --git a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
index 89a5b7b..9c37755 100644
--- a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -4629,31 +4629,48 @@
InstructionList.push_back(I);
break;
case bitc::FUNC_CODE_INST_PHI: { // PHI: [ty, val0,bb0, ...]
- if (Record.size() < 1 || ((Record.size()-1)&1))
+ if (Record.size() < 1)
return error("Invalid record");
+ // The first record specifies the type.
FullTy = getFullyStructuredTypeByID(Record[0]);
Type *Ty = flattenPointerTypes(FullTy);
if (!Ty)
return error("Invalid record");
- PHINode *PN = PHINode::Create(Ty, (Record.size()-1)/2);
+ // Phi arguments are pairs of records of [value, basic block].
+ // There is an optional final record for fast-math-flags if this phi has a
+ // floating-point type.
+ size_t NumArgs = (Record.size() - 1) / 2;
+ if ((Record.size() - 1) % 2 == 1 && !Ty->isFloatingPointTy())
+ return error("Invalid record");
+
+ PHINode *PN = PHINode::Create(Ty, NumArgs);
InstructionList.push_back(PN);
- for (unsigned i = 0, e = Record.size()-1; i != e; i += 2) {
+ for (unsigned i = 0; i != NumArgs; i++) {
Value *V;
// With the new function encoding, it is possible that operands have
// negative IDs (for forward references). Use a signed VBR
// representation to keep the encoding small.
if (UseRelativeIDs)
- V = getValueSigned(Record, 1+i, NextValueNo, Ty);
+ V = getValueSigned(Record, i * 2 + 1, NextValueNo, Ty);
else
- V = getValue(Record, 1+i, NextValueNo, Ty);
- BasicBlock *BB = getBasicBlock(Record[2+i]);
+ V = getValue(Record, i * 2 + 1, NextValueNo, Ty);
+ BasicBlock *BB = getBasicBlock(Record[i * 2 + 2]);
if (!V || !BB)
return error("Invalid record");
PN->addIncoming(V, BB);
}
I = PN;
+
+ // If there are an even number of records, the final record must be FMF.
+ if (Record.size() % 2 == 0) {
+ assert(isa<FPMathOperator>(I) && "Unexpected phi type");
+ FastMathFlags FMF = getDecodedFastMathFlags(Record[Record.size() - 1]);
+ if (FMF.any())
+ I->setFastMathFlags(FMF);
+ }
+
break;
}
diff --git a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
index 0eea6dc..2818e84 100644
--- a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -2880,6 +2880,11 @@
pushValueSigned(PN.getIncomingValue(i), InstID, Vals64);
Vals64.push_back(VE.getValueID(PN.getIncomingBlock(i)));
}
+
+ uint64_t Flags = getOptimizationFlags(&I);
+ if (Flags != 0)
+ Vals64.push_back(Flags);
+
// Emit a Vals64 vector and exit.
Stream.EmitRecord(Code, Vals64, AbbrevToUse);
Vals64.clear();