[PATCH] D159160: [SCEV] Fix potentially empty set for unsigned ranges

[Tejas Joshi via Phabricator via llvm-commits]

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The following commit enabled the analysis of ranges for heap allocations:
22ca38da25e19a7c5fcfeb3f22159aba92ec381e <https://reviews.llvm.org/rG22ca38da25e19a7c5fcfeb3f22159aba92ec381e>

The range turns out to be empty in cases such as the one in test (which
is [1,1)), leading to an assertion failure. This patch fixes for the
same case.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D159160

Files:
  llvm/lib/Analysis/ScalarEvolution.cpp
  llvm/test/Analysis/ScalarEvolution/malloc.ll


Index: llvm/test/Analysis/ScalarEvolution/malloc.ll
===================================================================
--- llvm/test/Analysis/ScalarEvolution/malloc.ll
+++ llvm/test/Analysis/ScalarEvolution/malloc.ll
@@ -23,4 +23,15 @@
   ret ptr %alloc
 }
 
+define ptr @undefined_max() {
+; CHECK-LABEL: 'undefined_max'
+; CHECK-NEXT:  Classifying expressions for: @undefined_max
+; CHECK-NEXT:    %alloc = call nonnull ptr @malloc(i64 -1)
+; CHECK-NEXT:    -->  %alloc U: full-set S: full-set
+; CHECK-NEXT:  Determining loop execution counts for: @undefined_max
+;
+    %alloc = call nonnull ptr @malloc(i64 -1)
+  ret ptr %alloc
+}
+
 declare noalias noundef ptr @malloc(i64 noundef) allockind("alloc,uninitialized") allocsize(0)
Index: llvm/lib/Analysis/ScalarEvolution.cpp
===================================================================
--- llvm/lib/Analysis/ScalarEvolution.cpp
+++ llvm/lib/Analysis/ScalarEvolution.cpp
@@ -6843,7 +6843,7 @@
         if (llvm::isKnownNonZero(V, DL))
           MinVal = Align;
         ConservativeResult = ConservativeResult.intersectWith(
-            {MinVal, MaxVal + 1}, RangeType);
+            ConstantRange::getNonEmpty(MinVal, MaxVal + 1), RangeType);
       }
     }
 


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