extend binop folds for selects to include true and false binops flag intersection

[mcberg2017]

Summary

This change address bug 38641

[mcberg2017]

The select_meta test has a directly related case in it that maps to the bug test case in https://bugs.llvm.org/show_bug.cgi?id=38641

[spatel]

Add a test with FMF too since that was the motivation for rL339938?
Code change LGTM.

[mcberg2017]

Actually the other test in rL339938 shows the positive side, where both binops are fast to show the intersection in /test/Transforms/LoopVectorize/reduction.ll

llvm/trunk/lib/Transforms/InstCombine/InstCombineSelect.cpp

Instruction *InstCombiner::foldSelectOpOp(SelectInst &SI, Instruction *TI,
 
   // If we reach here, they do have operations in common.
   Value *NewSI = Builder.CreateSelect(SI.getCondition(), OtherOpT, OtherOpF,
                                       SI.getName() + ".v", &SI);
   Value *Op0 = MatchIsOpZero ? MatchOp : NewSI;
   Value *Op1 = MatchIsOpZero ? NewSI : MatchOp;
   if (auto *BO = dyn_cast<BinaryOperator>(TI)) {
     BinaryOperator *NewBO = BinaryOperator::Create(BO->getOpcode(), Op0, Op1);
-    NewBO->copyIRFlags(BO);
+    NewBO->copyIRFlags(TI);
+    NewBO->andIRFlags(FI);
     return NewBO;
   }
   if (auto *TGEP = dyn_cast<GetElementPtrInst>(TI)) {
     auto *FGEP = cast<GetElementPtrInst>(FI);
     Type *ElementType = TGEP->getResultElementType();
     return TGEP->isInBounds() && FGEP->isInBounds()
                ? GetElementPtrInst::CreateInBounds(ElementType, Op0, {Op1})
                : GetElementPtrInst::Create(ElementType, Op0, {Op1});

llvm/trunk/test/Transforms/InstCombine/select_meta.ll

 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
 ; and enhanced to include metadata checking.
 
 ; RUN: opt < %s -instcombine -S | FileCheck %s
 
 define i32 @foo(i32) local_unnamed_addr #0  {
 ; CHECK-LABEL: @foo(
 ; CHECK-NEXT:    [[TMP2:%.*]] = icmp sgt i32 %0, 2
 ; CHECK-NEXT:    [[DOTV:%.*]] = select i1 [[TMP2]], i32 20, i32 -20, !prof ![[$MD1:[0-9]+]]
-; CHECK-NEXT:    [[TMP3:%.*]] = add nsw i32 [[DOTV]], %0
+; CHECK-NEXT:    [[TMP3:%.*]] = add i32 [[DOTV]], %0
 ; CHECK-NEXT:    ret i32 [[TMP3]]
 ;
   %2 = icmp sgt i32 %0, 2
   %3 = add nsw i32 %0, 20
-  %4 = add nsw i32 %0, -20
+  %4 = add i32 %0, -20
   select i1 %2, i32 %3, i32 %4, !prof !1
   ret i32 %5
 }
 
 define i8 @shrink_select(i1 %cond, i32 %x) {
 ; CHECK-LABEL: @shrink_select(
 ; CHECK-NEXT:    [[TMP1:%.*]] = trunc i32 %x to i8
 ; CHECK-NEXT:    [[TRUNC:%.*]] = select i1 %cond, i8 [[TMP1]], i8 42, !prof ![[$MD1]]