[dse] Skip llvm.allow.{runtime,ubsan}.check()

[vitalybuka]

Doing this because it's similar to assume, but I
can't see a difference neither for assume nor for
allow.

RFC: https://discourse.llvm.org/t/rfc-add-llvm-experimental-hot-intrinsic-or-llvm-hot/77641

[llvmbot]

@llvm/pr-subscribers-llvm-transforms

Author: Vitaly Buka (vitalybuka)

Changes

Doing this because it's similar to assume, but I
can't see a difference neither for assume nor for
allow.

RFC: https://discourse.llvm.org/t/rfc-add-llvm-experimental-hot-intrinsic-or-llvm-hot/77641

---

Full diff: https://github.com/llvm/llvm-project/pull/86067.diff

2 Files Affected:

• (modified) llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp (+2)
• (modified) llvm/test/Transforms/DeadStoreElimination/libcalls.ll (+17)

diff --git a/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp b/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
index bfc8bd5970bf27..5a9ea420392f75 100644
--- a/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
+++ b/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
@@ -760,6 +760,8 @@ namespace {
 bool isNoopIntrinsic(Instruction *I) {
   if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
     switch (II->getIntrinsicID()) {
+    case Intrinsic::allow_runtime_check:
+    case Intrinsic::allow_ubsan_check:
     case Intrinsic::lifetime_start:
     case Intrinsic::lifetime_end:
     case Intrinsic::invariant_end:
diff --git a/llvm/test/Transforms/DeadStoreElimination/libcalls.ll b/llvm/test/Transforms/DeadStoreElimination/libcalls.ll
index 4d9a767e08d490..7a4908d550a96a 100644
--- a/llvm/test/Transforms/DeadStoreElimination/libcalls.ll
+++ b/llvm/test/Transforms/DeadStoreElimination/libcalls.ll
@@ -487,3 +487,20 @@ define void @dse_strncpy_test6(ptr noalias %out1, ptr noalias %out2, ptr noalias
   %call = tail call ptr @strncpy(ptr %out2, ptr %in, i64 100)
   ret void
 }
+
+define i32 @test_strcat_with_allow_check(ptr %src) {
+; CHECK-LABEL: @test_strcat_with_allow_check(
+; CHECK-NEXT:    [[ALLOW1:%.*]] = call i1 @llvm.allow.runtime.check(metadata !"test_check")
+; CHECK-NEXT:    [[ALLOW2:%.*]] = call i1 @llvm.allow.ubsan.check(i8 7)
+; CHECK-NEXT:    tail call void @llvm.memset.p0.i64(ptr [[B:%.*]], i8 44, i64 16, i1 false)
+; CHECK-NEXT:    [[RET:%.*]] = load i32, ptr [[B]], align 4
+; CHECK-NEXT:    ret i32 [[RET]]
+;
+  tail call void @llvm.memset.p0.i64(ptr %src, i8 42, i64 16, i1 false)
+  %allow1 = call i1 @llvm.allow.runtime.check(metadata !"test_check")
+  tail call void @llvm.memset.p0.i64(ptr %src, i8 43, i64 16, i1 false)
+  %allow2 = call i1 @llvm.allow.ubsan.check(i8 7)
+  tail call void @llvm.memset.p0.i64(ptr %src, i8 44, i64 16, i1 false)
+  %ret = load i32, ptr %src, align 4
+  ret i32 %ret
+}

[nikic]

I don't think that this change is necessary. The InaccessibleMemOnly modelling will take care of it.

[vitalybuka]

I don't think that this change is necessary. The InaccessibleMemOnly modelling will take care of it.

Thanks. That makes sense. As I wrote in description, I tried to trigger code difference in tests, but failed for these and for assume.
Converting to draft.