[PATCH] D76446: [ConstantRange] Use APInt::or/APInt::and for single elements.

[Florian Hahn via Phabricator via llvm-commits]

fhahn created this revision.
fhahn added reviewers: nikic, spatel, lebedev.ri.
Herald added a subscriber: hiraditya.
Herald added a project: LLVM.

Currently ConstantRange::binaryAnd/binaryOr results are too pessimistic
for single element constant ranges.

If both operands are single element ranges, we can use APInt's AND and
OR implementations directly.

Note that some other binary operations on constant ranges can cover the
single element cases naturally, but for OR and AND this unfortunately is
not the case.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D76446

Files:
  llvm/lib/IR/ConstantRange.cpp
  llvm/test/Transforms/CorrelatedValuePropagation/range.ll


Index: llvm/test/Transforms/CorrelatedValuePropagation/range.ll
===================================================================
--- llvm/test/Transforms/CorrelatedValuePropagation/range.ll
+++ llvm/test/Transforms/CorrelatedValuePropagation/range.ll
@@ -457,7 +457,7 @@
 ; CHECK-NEXT:    br i1 [[CMP]], label [[THEN:%.*]], label [[ELSE:%.*]]
 ; CHECK:       then:
 ; CHECK-NEXT:    [[RESULT:%.*]] = or i1 false, false
-; CHECK-NEXT:    ret i1 [[RESULT]]
+; CHECK-NEXT:    ret i1 false
 ; CHECK:       else:
 ; CHECK-NEXT:    ret i1 false
 ;
@@ -508,7 +508,7 @@
 ; CHECK-NEXT:    br i1 [[CMP]], label [[THEN:%.*]], label [[ELSE:%.*]]
 ; CHECK:       then:
 ; CHECK-NEXT:    [[RESULT:%.*]] = or i1 false, false
-; CHECK-NEXT:    ret i1 [[RESULT]]
+; CHECK-NEXT:    ret i1 false
 ; CHECK:       else:
 ; CHECK-NEXT:    ret i1 false
 ;
@@ -585,7 +585,7 @@
 ; CHECK-NEXT:    br i1 [[CMP]], label [[THEN:%.*]], label [[ELSE:%.*]]
 ; CHECK:       then:
 ; CHECK-NEXT:    [[RESULT:%.*]] = or i1 false, false
-; CHECK-NEXT:    ret i1 [[RESULT]]
+; CHECK-NEXT:    ret i1 false
 ; CHECK:       else:
 ; CHECK-NEXT:    ret i1 false
 ;
@@ -629,6 +629,32 @@
   ret i1 false
 }
 
+define i1 @test14_ugt_and(i32 %a) {
+; CHECK-LABEL: @test14_ugt_and(
+; CHECK-NEXT:    [[A_OFF:%.*]] = add i32 [[A:%.*]], -8
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ugt i32 [[A_OFF]], 8
+; CHECK-NEXT:    br i1 [[CMP]], label [[THEN:%.*]], label [[ELSE:%.*]]
+; CHECK:       then:
+; CHECK-NEXT:    [[RESULT:%.*]] = and i1 false, false
+; CHECK-NEXT:    ret i1 false
+; CHECK:       else:
+; CHECK-NEXT:    ret i1 false
+;
+  %a.off = add i32 %a, -8
+  %cmp = icmp ugt i32 %a.off, 8
+  br i1 %cmp, label %then, label %else
+
+then:
+  %dead.1 = icmp eq i32 %a, 8
+  %dead.2 = icmp eq i32 %a, 16
+  %result = and i1 %dead.1, %dead.2
+  ret i1 %result
+
+else:
+  ret i1 false
+}
+
+
 @limit = external global i32
 define i1 @test15(i32 %a) {
 ; CHECK-LABEL: @test15(
Index: llvm/lib/IR/ConstantRange.cpp
===================================================================
--- llvm/lib/IR/ConstantRange.cpp
+++ llvm/lib/IR/ConstantRange.cpp
@@ -1194,6 +1194,10 @@
   if (isEmptySet() || Other.isEmptySet())
     return getEmpty();
 
+  // Use APInt's implementation of AND for single element ranges.
+  if (isSingleElement() && Other.isSingleElement())
+    return {*getSingleElement() & *Other.getSingleElement()};
+
   // TODO: replace this with something less conservative
 
   APInt umin = APIntOps::umin(Other.getUnsignedMax(), getUnsignedMax());
@@ -1205,6 +1209,10 @@
   if (isEmptySet() || Other.isEmptySet())
     return getEmpty();
 
+  // Use APInt's implementation of OR for single element ranges.
+  if (isSingleElement() && Other.isSingleElement())
+    return {*getSingleElement() | *Other.getSingleElement()};
+
   // TODO: replace this with something less conservative
 
   APInt umax = APIntOps::umax(getUnsignedMin(), Other.getUnsignedMin());


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