Revert "[LSR] Avoid UB overflow when examining reuse opportunities"

This reverts commit r324943.

Breaking bots, reverting for Gerolf.

llvm-svn: 324958

2 files changed, 0 insertions, 31 deletions

diff --git a/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp b/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
index 8b6e5e34b40..b7d9a258913 100644
--- a/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
@@ -3939,11 +3939,6 @@ void LSRInstance::GenerateCrossUseConstantOffsets() {
     if (Imms.size() == 1)
       continue;
 
-    // UB: Check for overflow
-    int64_t Res;
-    if (__builtin_saddll_overflow(Imms.begin()->first, std::prev(Imms.end())->first, &Res))
-      continue;
-
     DEBUG(dbgs() << "Generating cross-use offsets for " << *Reg << ':';
           for (const auto &Entry : Imms)
             dbgs() << ' ' << Entry.first;
diff --git a/llvm/test/CodeGen/X86/loop-strength-reduce-overflow-check.ll b/llvm/test/CodeGen/X86/loop-strength-reduce-overflow-check.ll
deleted file mode 100644
index 35e3433c701..00000000000
--- a/llvm/test/CodeGen/X86/loop-strength-reduce-overflow-check.ll
+++ /dev/null
@@ -1,26 +0,0 @@
-; RUN: llc < %s -O1 -mtriple=x86_64-unknown-unknown
-
-; LSR has to check for overflow to avoid UB when it examines reuse opportunities
-; Clang built with UBSan would expose the issue in this test case
-
-define void @main() {
-bb:
-  br label %bb1
-
-bb1:                                              ; preds = %bb1, %bb
-  %tmp = phi i64 [ 248268322795906120, %bb ], [ %tmp10, %bb1 ]
-  %tmp2 = sub i64 %tmp, 248268322795906120
-  %tmp3 = getelementptr i8, i8* undef, i64 %tmp2
-  %tmp4 = sub i64 %tmp, 248268322795906120
-  %tmp5 = getelementptr i8, i8* undef, i64 %tmp4
-  %tmp6 = getelementptr i8, i8* %tmp5, i64 -9086989864993762928
-  %tmp7 = load i8, i8* %tmp6, align 1
-  %tmp8 = getelementptr i8, i8* %tmp3, i64 -1931736422337600660
-  store i8 undef, i8* %tmp8
-  %tmp9 = add i64 %tmp, 248268322795906121
-  %tmp10 = add i64 %tmp9, -248268322795906120
-  br i1 undef, label %bb11, label %bb1
-
-bb11:                                             ; preds = %bb1
-  ret void
-}