When comparing constants, consider a less wide constant to be "less complex"

than a wider one, before trying to compare their contents which will crash
if their sizes are different.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@74792 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 18 insertions, 0 deletions

diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp
index 408156265d..aa4b58661c 100644
--- a/lib/Analysis/ScalarEvolution.cpp
+++ b/lib/Analysis/ScalarEvolution.cpp
@@ -495,6 +495,8 @@ namespace {
       // Compare constant values.
       if (const SCEVConstant *LC = dyn_cast<SCEVConstant>(LHS)) {
         const SCEVConstant *RC = cast<SCEVConstant>(RHS);
+        if (LC->getValue()->getBitWidth() != RC->getValue()->getBitWidth())
+          return LC->getValue()->getBitWidth() < RC->getValue()->getBitWidth();
         return LC->getValue()->getValue().ult(RC->getValue()->getValue());
       }
 
diff --git a/test/Analysis/ScalarEvolution/2009-07-04-GroupConstantsWidthMismatch.ll b/test/Analysis/ScalarEvolution/2009-07-04-GroupConstantsWidthMismatch.ll
new file mode 100644
index 0000000000..b5d588e01a
--- /dev/null
+++ b/test/Analysis/ScalarEvolution/2009-07-04-GroupConstantsWidthMismatch.ll
@@ -0,0 +1,16 @@
+; RUN: llvm-as < %s | opt -analyze -scalar-evolution
+; PR4501
+
+define void @test() {
+entry:
+        %0 = load i16* undef, align 1
+        %1 = lshr i16 %0, 8
+        %2 = and i16 %1, 3
+        %3 = zext i16 %2 to i32
+        %4 = load i8* undef, align 1
+        %5 = lshr i8 %4, 4
+        %6 = and i8 %5, 1
+        %7 = zext i8 %6 to i32
+        %t1 = add i32 %3, %7
+        ret void
+}