When checking for signed multiplication overflow, watch out for INT_MIN and -1.

This fixes PR9845.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@131919 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Scalar/LoopStrengthReduce.cpp b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
index 204ce36b8a499a54f63de9d2ab1e912cda5c91ea..73ebd618a0cbe6fb5c8c2c8fa97234382d2ecd58 100644 (file)
--- a/lib/Transforms/Scalar/LoopStrengthReduce.cpp
+++ b/lib/Transforms/Scalar/LoopStrengthReduce.cpp
@@ -2522,6 +2522,8 @@ void LSRInstance::GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx,
 
     // Check that multiplying with the unfolded offset doesn't overflow.
     if (F.UnfoldedOffset != 0) {
+      if (F.UnfoldedOffset == INT64_MIN && Factor == -1)
+        continue;
       F.UnfoldedOffset = (uint64_t)F.UnfoldedOffset * Factor;
       if (F.UnfoldedOffset / Factor != Base.UnfoldedOffset)
         continue;

diff --git a/test/CodeGen/X86/lsr-overflow.ll b/test/CodeGen/X86/lsr-overflow.ll
index 5bc4f7e96a0b9d28e3927e6ebba2aa1ac4bfad3e..09c1c07ef3de01d0bbf9c01267608e2e38b81f3a 100644 (file)
--- a/test/CodeGen/X86/lsr-overflow.ll
+++ b/test/CodeGen/X86/lsr-overflow.ll
@@ -25,3 +25,21 @@ __ABContainsLabel.exit:
   %cmp = icmp eq i64 %indvar, 9223372036854775807
   ret i1 %cmp
 }
+
+define void @func_37() noreturn nounwind readonly {
+entry:
+  br label %for.body
+
+for.body:                                         ; preds = %for.inc8, %entry
+  %indvar = phi i64 [ 0, %entry ], [ %indvar.next, %for.inc8 ]
+  %sub.i = add i64 undef, %indvar
+  %cmp.i = icmp eq i64 %sub.i, -9223372036854775808
+  br i1 undef, label %for.inc8, label %for.cond4
+
+for.cond4:                                        ; preds = %for.cond4, %for.body
+  br label %for.cond4
+
+for.inc8:                                         ; preds = %for.body
+  %indvar.next = add i64 %indvar, 1
+  br label %for.body
+}