[LVI][CVP] Add support for abs/nabs select pattern flavor

[nikic]

Summary

Based on ConstantRange support added in D61084, we can now handle abs and nabs select pattern flavors in LVI.

[lebedev.ri]

This looks good to me, but would be good if someone else familiar with CVP could review.

[spatel]

Still not too familiar with CVP, but this is another straightforward extension, so LGTM.

llvm/trunk/lib/Analysis/LazyValueInfo.cpp

if (SelectPatternResult::isMinOrMax(SPR.Flavor) &&
         case SPF_UMAX:                   /// Unsigned maximum
           return TrueCR.umax(FalseCR);
         };
       }();
       BBLV = ValueLatticeElement::getRange(ResultCR);
       return true;
     }
 
-    // TODO: ABS, NABS from the SelectPatternResult
+    if (SPR.Flavor == SPF_ABS) {
+      if (LHS == SI->getTrueValue()) {
+        BBLV = ValueLatticeElement::getRange(TrueCR.abs());
+        return true;
+      }
+      if (LHS == SI->getFalseValue()) {
+        BBLV = ValueLatticeElement::getRange(FalseCR.abs());
+        return true;
+      }
+    }
+
+    if (SPR.Flavor == SPF_NABS) {
+      ConstantRange Zero(APInt::getNullValue(TrueCR.getBitWidth()));
+      if (LHS == SI->getTrueValue()) {
+        BBLV = ValueLatticeElement::getRange(Zero.sub(TrueCR.abs()));
+        return true;
+      }
+      if (LHS == SI->getFalseValue()) {
+        BBLV = ValueLatticeElement::getRange(Zero.sub(FalseCR.abs()));
+        return true;
+      }
+    }
   }
 
   // Can we constrain the facts about the true and false values by using the
   // condition itself?  This shows up with idioms like e.g. select(a > 5, a, 5).
   // TODO: We could potentially refine an overdefined true value above.
   Value *Cond = SI->getCondition();
   TrueVal = intersect(TrueVal,
                       getValueFromCondition(SI->getTrueValue(), Cond, true));

llvm/trunk/test/Transforms/CorrelatedValuePropagation/basic.ll

 ; CHECK-NEXT:    [[SUB:%.*]] = sub i32 0, [[A]]
 ; CHECK-NEXT:    [[CMP:%.*]] = icmp slt i32 [[A]], 0
 ; CHECK-NEXT:    [[ABS:%.*]] = select i1 [[CMP]], i32 [[SUB]], i32 [[A]]
 ; CHECK-NEXT:    br label [[SPLIT:%.*]]
 ; CHECK:       split:
 ; CHECK-NEXT:    store i1 true, i1* [[P:%.*]]
 ; CHECK-NEXT:    [[C2:%.*]] = icmp slt i32 [[ABS]], 19
 ; CHECK-NEXT:    store i1 [[C2]], i1* [[P]]
-; CHECK-NEXT:    [[C3:%.*]] = icmp sge i32 [[ABS]], 0
-; CHECK-NEXT:    store i1 [[C3]], i1* [[P]]
+; CHECK-NEXT:    store i1 true, i1* [[P]]
 ; CHECK-NEXT:    [[C4:%.*]] = icmp sge i32 [[ABS]], 1
 ; CHECK-NEXT:    store i1 [[C4]], i1* [[P]]
 ; CHECK-NEXT:    br label [[EXIT]]
 ; CHECK:       exit:
 ; CHECK-NEXT:    ret void
 ;
 entry:
   %cmp1 = icmp slt i32 %a, 10

 ; CHECK-NEXT:    [[SUB:%.*]] = sub i32 0, [[A]]
 ; CHECK-NEXT:    [[CMP:%.*]] = icmp sge i32 [[A]], 0
 ; CHECK-NEXT:    [[ABS:%.*]] = select i1 [[CMP]], i32 [[A]], i32 [[SUB]]
 ; CHECK-NEXT:    br label [[SPLIT:%.*]]
 ; CHECK:       split:
 ; CHECK-NEXT:    store i1 true, i1* [[P:%.*]]
 ; CHECK-NEXT:    [[C2:%.*]] = icmp slt i32 [[ABS]], 19
 ; CHECK-NEXT:    store i1 [[C2]], i1* [[P]]
-; CHECK-NEXT:    [[C3:%.*]] = icmp sge i32 [[ABS]], 0
-; CHECK-NEXT:    store i1 [[C3]], i1* [[P]]
+; CHECK-NEXT:    store i1 true, i1* [[P]]
 ; CHECK-NEXT:    [[C4:%.*]] = icmp sge i32 [[ABS]], 1
 ; CHECK-NEXT:    store i1 [[C4]], i1* [[P]]
 ; CHECK-NEXT:    br label [[EXIT]]
 ; CHECK:       exit:
 ; CHECK-NEXT:    ret void
 ;
 entry:
   %cmp1 = icmp slt i32 %a, 10

 ; CHECK-NEXT:    [[SUB:%.*]] = sub i32 0, [[A]]
 ; CHECK-NEXT:    [[CMP:%.*]] = icmp sgt i32 [[A]], 0
 ; CHECK-NEXT:    [[NABS:%.*]] = select i1 [[CMP]], i32 [[SUB]], i32 [[A]]
 ; CHECK-NEXT:    br label [[SPLIT:%.*]]
 ; CHECK:       split:
 ; CHECK-NEXT:    store i1 true, i1* [[P:%.*]]
 ; CHECK-NEXT:    [[C2:%.*]] = icmp sgt i32 [[NABS]], -19
 ; CHECK-NEXT:    store i1 [[C2]], i1* [[P]]
-; CHECK-NEXT:    [[C3:%.*]] = icmp sle i32 [[NABS]], 0
-; CHECK-NEXT:    store i1 [[C3]], i1* [[P]]
+; CHECK-NEXT:    store i1 true, i1* [[P]]
 ; CHECK-NEXT:    [[C4:%.*]] = icmp sle i32 [[NABS]], -1
 ; CHECK-NEXT:    store i1 [[C4]], i1* [[P]]
 ; CHECK-NEXT:    br label [[EXIT]]
 ; CHECK:       exit:
 ; CHECK-NEXT:    ret void
 ;
 entry:
   %cmp1 = icmp slt i32 %a, 10

 ; CHECK-NEXT:    [[SUB:%.*]] = sub i32 0, [[A]]
 ; CHECK-NEXT:    [[CMP:%.*]] = icmp slt i32 [[A]], 0
 ; CHECK-NEXT:    [[NABS:%.*]] = select i1 [[CMP]], i32 [[A]], i32 [[SUB]]
 ; CHECK-NEXT:    br label [[SPLIT:%.*]]
 ; CHECK:       split:
 ; CHECK-NEXT:    store i1 true, i1* [[P:%.*]]
 ; CHECK-NEXT:    [[C2:%.*]] = icmp sgt i32 [[NABS]], -19
 ; CHECK-NEXT:    store i1 [[C2]], i1* [[P]]
-; CHECK-NEXT:    [[C3:%.*]] = icmp sle i32 [[NABS]], 0
-; CHECK-NEXT:    store i1 [[C3]], i1* [[P]]
+; CHECK-NEXT:    store i1 true, i1* [[P]]
 ; CHECK-NEXT:    [[C4:%.*]] = icmp sle i32 [[NABS]], -1
 ; CHECK-NEXT:    store i1 [[C4]], i1* [[P]]
 ; CHECK-NEXT:    br label [[EXIT]]
 ; CHECK:       exit:
 ; CHECK-NEXT:    ret void
 ;
 entry:
   %cmp1 = icmp slt i32 %a, 10