[Scalarizer] Propagate IR flags

[foad]

Summary

The motivation for this was to propagate fast-math flags like nnan and
ninf on vector floating point operations to the corresponding scalar
operations to take advantage of follow-on optimizations. But I think
the same argument applies to all of our IR flags: if they apply to the
vector operation then they also apply to all the individual scalar
operations, and they might enable follow-on optimizations.

[foad]

Hoping for review from someone outside AMD.

[arsenm]

llvm/test/Transforms/Scalarizer/basic.ll

531

Can you also add a test for fneg, and an intrinsic or 2

[foad]

Add fneg test.

[foad]

llvm/test/Transforms/Scalarizer/basic.ll

531

fneg: done. Intrinsics are CallInsts which don't have any IR flags.

[arsenm]

llvm/test/Transforms/Scalarizer/basic.ll

531

Yes they do. Also, fcmp is another strange case to test

[foad]

Add fcmp and intrinsic tests.

[foad]

llvm/test/Transforms/Scalarizer/basic.ll

531

Good point. Done.

[arsenm]

LGTM

llvm/lib/Transforms/Scalar/Scalarizer.cpp

public:
   bool visitLoadInst(LoadInst &LI);
   bool visitStoreInst(StoreInst &SI);
   bool visitCallInst(CallInst &ICI);
 
 private:
   Scatterer scatter(Instruction *Point, Value *V);
   void gather(Instruction *Op, const ValueVector &CV);
   bool canTransferMetadata(unsigned Kind);
-  void transferMetadata(Instruction *Op, const ValueVector &CV);
+  void transferMetadataAndIRFlags(Instruction *Op, const ValueVector &CV);
   bool getVectorLayout(Type *Ty, unsigned Alignment, VectorLayout &Layout,
                        const DataLayout &DL);
   bool finish();
 
   template<typename T> bool splitUnary(Instruction &, const T &);
   template<typename T> bool splitBinary(Instruction &, const T &);
 
   bool splitCall(CallInst &CI);

 // so that we can avoid creating the gathered form if all uses of Op are
 // replaced with uses of CV.
 void ScalarizerVisitor::gather(Instruction *Op, const ValueVector &CV) {
   // Since we're not deleting Op yet, stub out its operands, so that it
   // doesn't make anything live unnecessarily.
   for (unsigned I = 0, E = Op->getNumOperands(); I != E; ++I)
     Op->setOperand(I, UndefValue::get(Op->getOperand(I)->getType()));
 
-  transferMetadata(Op, CV);
+  transferMetadataAndIRFlags(Op, CV);
 
   // If we already have a scattered form of Op (created from ExtractElements
   // of Op itself), replace them with the new form.
   ValueVector &SV = Scattered[Op];
   if (!SV.empty()) {
     for (unsigned I = 0, E = SV.size(); I != E; ++I) {
       Value *V = SV[I];
       if (V == nullptr)
return (Tag == LLVMContext::MD_tbaa
           || Tag == LLVMContext::MD_alias_scope
           || Tag == LLVMContext::MD_noalias
           || Tag == ParallelLoopAccessMDKind
           || Tag == LLVMContext::MD_access_group);
 }
 
 // Transfer metadata from Op to the instructions in CV if it is known
 // to be safe to do so.
-void ScalarizerVisitor::transferMetadata(Instruction *Op, const ValueVector &CV) {
+void ScalarizerVisitor::transferMetadataAndIRFlags(Instruction *Op,
+                                                   const ValueVector &CV) {
   SmallVector<std::pair<unsigned, MDNode *>, 4> MDs;
   Op->getAllMetadataOtherThanDebugLoc(MDs);
   for (unsigned I = 0, E = CV.size(); I != E; ++I) {
     if (Instruction *New = dyn_cast<Instruction>(CV[I])) {
       for (const auto &MD : MDs)
         if (canTransferMetadata(MD.first))
           New->setMetadata(MD.first, MD.second);
+      New->copyIRFlags(Op);
       if (Op->getDebugLoc() && !New->getDebugLoc())
         New->setDebugLoc(Op->getDebugLoc());
     }
   }
 }
 
 // Try to fill in Layout from Ty, returning true on success.  Alignment is
 // the alignment of the vector, or 0 if the ABI default should be used.
bool ScalarizerVisitor::visitStoreInst(StoreInst &SI) {
   Scatterer Val = scatter(&SI, FullValue);
 
   ValueVector Stores;
   Stores.resize(NumElems);
   for (unsigned I = 0; I < NumElems; ++I) {
     unsigned Align = Layout.getElemAlign(I);
     Stores[I] = Builder.CreateAlignedStore(Val[I], Ptr[I], Align);
   }
-  transferMetadata(&SI, Stores);
+  transferMetadataAndIRFlags(&SI, Stores);
   return true;
 }
 
 bool ScalarizerVisitor::visitCallInst(CallInst &CI) {
   return splitCall(CI);
 }
 
 // Delete the instructions that we scalarized.  If a full vector result

llvm/test/Transforms/Scalarizer/basic.ll

loop:
 
   %test = icmp eq i32 %nexti, 0
   br i1 %test, label %loop, label %exit
 
 exit:
   ret void
 }
 
+; Check that IR flags are preserved.
+define <2 x i32> @f16(<2 x i32> %i, <2 x i32> %j) {
+; CHECK-LABEL: @f16(
+; CHECK: %res.i0 = add nuw nsw i32
+; CHECK: %res.i1 = add nuw nsw i32
+  %res = add nuw nsw <2 x i32> %i, %j
+  ret <2 x i32> %res
+}
+define <2 x i32> @f17(<2 x i32> %i, <2 x i32> %j) {
+; CHECK-LABEL: @f17(
+; CHECK: %res.i0 = sdiv exact i32
+; CHECK: %res.i1 = sdiv exact i32
+  %res = sdiv exact <2 x i32> %i, %j
+  ret <2 x i32> %res
+}
+define <2 x float> @f18(<2 x float> %x, <2 x float> %y) {
+; CHECK-LABEL: @f18(
+; CHECK: %res.i0 = fadd fast float
+; CHECK: %res.i1 = fadd fast float
+  %res = fadd fast <2 x float> %x, %y
+  ret <2 x float> %res
+}
+
 !0 = !{ !"root" }
 !1 = !{ !"set1", !0 }
 !2 = !{ !"set2", !0 }
 !3 = !{ !3, !{!"llvm.loop.parallel_accesses", !13} }
 !4 = !{ float 4.0 }
 !5 = !{ i64 0, i64 8, null }
 !13 = distinct !{}