[PATCH] D148456: [SROA] Unconditionally load is unsafe with nonnull and noundef metadata.

[DianQK via Phabricator via llvm-commits]

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Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D148456

Files:
  llvm/lib/Analysis/Loads.cpp
  llvm/test/Transforms/SROA/select-load-with-nonnull.ll


Index: llvm/test/Transforms/SROA/select-load-with-nonnull.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/SROA/select-load-with-nonnull.ll
@@ -0,0 +1,56 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -passes='sroa<modify-cfg>' -S | FileCheck %s
+
+define void @load_of_select_with_noundef_nonnull(ptr %buffer, i1 %b) {
+; CHECK-LABEL: @load_of_select_with_noundef_nonnull(
+; CHECK-NEXT:    br i1 [[B:%.*]], label [[DOTTHEN:%.*]], label [[DOTELSE:%.*]]
+; CHECK:       .then:
+; CHECK-NEXT:    [[LOAD_PTR_THEN_VAL:%.*]] = load ptr, ptr [[BUFFER:%.*]], align 8, !nonnull !0, !noundef !0
+; CHECK-NEXT:    br label [[DOTCONT:%.*]]
+; CHECK:       .else:
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp ne ptr undef, null
+; CHECK-NEXT:    call void @llvm.assume(i1 [[TMP1]])
+; CHECK-NEXT:    br label [[DOTCONT]]
+; CHECK:       .cont:
+; CHECK-NEXT:    [[LOAD_PTR:%.*]] = phi ptr [ [[LOAD_PTR_THEN_VAL]], [[DOTTHEN]] ], [ undef, [[DOTELSE]] ]
+; CHECK-NEXT:    ret void
+;
+  %ub_ptr = alloca ptr
+  %select_ptr = select i1 %b, ptr %buffer, ptr %ub_ptr
+  %load_ptr = load ptr, ptr %select_ptr, !nonnull !1, !noundef !1
+  ret void
+}
+
+define void @load_of_select_with_noundef(ptr %buffer, i1 %b) {
+; CHECK-LABEL: @load_of_select_with_noundef(
+; CHECK-NEXT:    br i1 [[B:%.*]], label [[DOTTHEN:%.*]], label [[DOTCONT:%.*]]
+; CHECK:       .then:
+; CHECK-NEXT:    [[LOAD_PTR_THEN_VAL:%.*]] = load ptr, ptr [[BUFFER:%.*]], align 8, !noundef !0
+; CHECK-NEXT:    br label [[DOTCONT]]
+; CHECK:       .cont:
+; CHECK-NEXT:    [[LOAD_PTR:%.*]] = phi ptr [ [[LOAD_PTR_THEN_VAL]], [[DOTTHEN]] ], [ undef, [[TMP0:%.*]] ]
+; CHECK-NEXT:    ret void
+;
+  %ub_ptr = alloca ptr
+  %select_ptr = select i1 %b, ptr %buffer, ptr %ub_ptr
+  %load_ptr = load ptr, ptr %select_ptr, !noundef !1
+  ret void
+}
+
+define void @load_of_select(ptr %buffer, i1 %b) {
+; CHECK-LABEL: @load_of_select(
+; CHECK-NEXT:    br i1 [[B:%.*]], label [[DOTTHEN:%.*]], label [[DOTCONT:%.*]]
+; CHECK:       .then:
+; CHECK-NEXT:    [[LOAD_PTR_THEN_VAL:%.*]] = load ptr, ptr [[BUFFER:%.*]], align 8
+; CHECK-NEXT:    br label [[DOTCONT]]
+; CHECK:       .cont:
+; CHECK-NEXT:    [[LOAD_PTR:%.*]] = phi ptr [ [[LOAD_PTR_THEN_VAL]], [[DOTTHEN]] ], [ undef, [[TMP0:%.*]] ]
+; CHECK-NEXT:    ret void
+;
+  %ub_ptr = alloca ptr
+  %select_ptr = select i1 %b, ptr %buffer, ptr %ub_ptr
+  %load_ptr = load ptr, ptr %select_ptr
+  ret void
+}
+
+!1 = !{}
Index: llvm/lib/Analysis/Loads.cpp
===================================================================
--- llvm/lib/Analysis/Loads.cpp
+++ llvm/lib/Analysis/Loads.cpp
@@ -435,6 +435,15 @@
   TypeSize TySize = DL.getTypeStoreSize(Ty);
   if (TySize.isScalable())
     return false;
+  // When the load has nonnull and noundef metadata, we cannot easily conclude
+  // that it is safe.
+  if (auto *LI = dyn_cast<LoadInst>(ScanFrom)) {
+    if (LI->getType()->isPointerTy() &&
+        LI->getMetadata(LLVMContext::MD_nonnull) &&
+        LI->getMetadata(LLVMContext::MD_noundef)) {
+      return false;
+    }
+  }
   APInt Size(DL.getIndexTypeSizeInBits(V->getType()), TySize.getFixedValue());
   return isSafeToLoadUnconditionally(V, Alignment, Size, DL, ScanFrom, AC, DT,
                                      TLI);


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