From: David Bolvansky <david.bolvansky@gmail.com>
Date: Tue, 13 Aug 2019 16:44:16 +0000 (+0000)
Subject: [SLC] Improve dereferenceable bytes annotation
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=e2ecc33d0b261e8e8d7c43cbfefa8d066d5edf4b;p=llvm

[SLC] Improve dereferenceable bytes annotation


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@368715 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Transforms/Utils/SimplifyLibCalls.cpp b/lib/Transforms/Utils/SimplifyLibCalls.cpp
index 396690e1860..ef4cc227222 100644
--- a/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ b/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -188,8 +188,12 @@ static bool canTransformToMemCmp(CallInst *CI, Value *Str, uint64_t Len,
 
 static void annotateDereferenceableBytes(CallInst *CI,
                                          ArrayRef<unsigned> ArgNos,
-                                         uint64_t DerefBytes) {
+                                         uint64_t DereferenceableBytes) {
   for (unsigned ArgNo : ArgNos) {
+    uint64_t DerefBytes = std::max(
+        CI->getDereferenceableOrNullBytes(ArgNo + AttributeList::FirstArgIndex),
+        DereferenceableBytes);
+
     if (CI->getDereferenceableBytes(ArgNo + AttributeList::FirstArgIndex) <
         DerefBytes) {
       CI->removeParamAttr(ArgNo, Attribute::Dereferenceable);
diff --git a/test/Transforms/InstCombine/mem-deref-bytes.ll b/test/Transforms/InstCombine/mem-deref-bytes.ll
index a329f9dcdaa..87be8f57795 100644
--- a/test/Transforms/InstCombine/mem-deref-bytes.ll
+++ b/test/Transforms/InstCombine/mem-deref-bytes.ll
@@ -48,7 +48,7 @@ define i32 @memcmp_const_size_no_update_deref(i8* nocapture readonly %d, i8* noc
 
 define i32 @memcmp_const_size_no_update_deref2(i8* nocapture readonly %d, i8* nocapture readonly %s) {
 ; CHECK-LABEL: @memcmp_const_size_no_update_deref2(
-; CHECK-NEXT:    [[CALL:%.*]] = tail call i32 @memcmp(i8* dereferenceable(16) [[D:%.*]], i8* dereferenceable(16) [[S:%.*]], i64 16)
+; CHECK-NEXT:    [[CALL:%.*]] = tail call i32 @memcmp(i8* dereferenceable(40) [[D:%.*]], i8* dereferenceable(16) [[S:%.*]], i64 16)
 ; CHECK-NEXT:    ret i32 [[CALL]]
 ;
   %call = tail call i32 @memcmp(i8* dereferenceable_or_null(40) %d, i8* %s, i64 16)