[SLC] Improve dereferenceable bytes annotation

davidbolvansky · davidbolvansky · commit 90a30fdcc39e · 2019-08-13T16:44:16.000Z
llvm-svn: 368715
diff --git a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp b/llvm/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/llvm/test/Transforms/InstCombine/mem-deref-bytes.ll b/llvm/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)

Original file line number	Diff line number	Diff line change
`@@ -48,7 +48,7 @@ define i32 @memcmp_const_size_no_update_deref(i8* nocapture readonly %d, i8* noc`
`48`	`48`
`49`	`49`	`define i32 @memcmp_const_size_no_update_deref2(i8* nocapture readonly %d, i8* nocapture readonly %s) {`
`50`	`50`	`; CHECK-LABEL: @memcmp_const_size_no_update_deref2(`
`51`		`-; CHECK-NEXT: [[CALL:%.]] = tail call i32 @memcmp(i8 dereferenceable(16) [[D:%.]], i8 dereferenceable(16) [[S:%.*]], i64 16)`
	`51`	`+; CHECK-NEXT: [[CALL:%.]] = tail call i32 @memcmp(i8 dereferenceable(40) [[D:%.]], i8 dereferenceable(16) [[S:%.*]], i64 16)`
`52`	`52`	`; CHECK-NEXT: ret i32 [[CALL]]`
`53`	`53`	`;`
`54`	`54`	`%call = tail call i32 @memcmp(i8* dereferenceable_or_null(40) %d, i8* %s, i64 16)`