[llvm] r372647 - [InstCombine] Annotate strndup calls with dereferenceable_or_null

[David Bolvansky via llvm-commits]

Author: xbolva00
Date: Mon Sep 23 12:55:45 2019
New Revision: 372647

URL: http://llvm.org/viewvc/llvm-project?rev=372647&view=rev
Log:
[InstCombine] Annotate strndup calls with dereferenceable_or_null

"Implementations are free to malloc() a buffer containing either (size + 1) bytes or (strnlen(s, size) + 1) bytes. Applications should not assume that strndup() will allocate (size + 1) bytes when strlen(s) is smaller than size."

Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp
    llvm/trunk/test/Transforms/InstCombine/objsize.ll
    llvm/trunk/test/Transforms/InstCombine/strndup.ll

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp?rev=372647&r1=372646&r2=372647&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp Mon Sep 23 12:55:45 2019
@@ -4179,10 +4179,10 @@ static IntrinsicInst *findInitTrampoline
 }
 
 static void annotateAnyAllocSite(CallBase &Call, const TargetLibraryInfo *TLI) {
+  unsigned NumArgs = Call.getNumArgOperands();
   ConstantInt *Op0C = dyn_cast<ConstantInt>(Call.getOperand(0));
-  ConstantInt *Op1C = (Call.getNumArgOperands() == 1)
-                          ? nullptr
-                          : dyn_cast<ConstantInt>(Call.getOperand(1));
+  ConstantInt *Op1C =
+      (NumArgs == 1) ? nullptr : dyn_cast<ConstantInt>(Call.getOperand(1));
   // Bail out if the allocation size is zero.
   if ((Op0C && Op0C->isNullValue()) || (Op1C && Op1C->isNullValue()))
     return;
@@ -4208,12 +4208,21 @@ static void annotateAnyAllocSite(CallBas
       Call.addAttribute(AttributeList::ReturnIndex,
                         Attribute::getWithDereferenceableOrNullBytes(
                             Call.getContext(), Size.getZExtValue()));
-  } else if (isStrdupLikeFn(&Call, TLI) && Call.getNumArgOperands() == 1) {
-    // TODO: handle strndup
-    if (uint64_t Len = GetStringLength(Call.getOperand(0)))
-      Call.addAttribute(
-          AttributeList::ReturnIndex,
-          Attribute::getWithDereferenceableOrNullBytes(Call.getContext(), Len));
+  } else if (isStrdupLikeFn(&Call, TLI)) {
+    uint64_t Len = GetStringLength(Call.getOperand(0));
+    if (Len) {
+      // strdup
+      if (NumArgs == 1)
+        Call.addAttribute(AttributeList::ReturnIndex,
+                          Attribute::getWithDereferenceableOrNullBytes(
+                              Call.getContext(), Len));
+      // strndup
+      else if (NumArgs == 2 && Op1C)
+        Call.addAttribute(
+            AttributeList::ReturnIndex,
+            Attribute::getWithDereferenceableOrNullBytes(
+                Call.getContext(), std::min(Len, Op1C->getZExtValue() + 1)));
+    }
   }
 }
 

Modified: llvm/trunk/test/Transforms/InstCombine/objsize.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/objsize.ll?rev=372647&r1=372646&r2=372647&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/objsize.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/objsize.ll Mon Sep 23 12:55:45 2019
@@ -239,7 +239,7 @@ define i32 @test9(i8** %esc) {
 
 define i32 @test10(i8** %esc) {
 ; CHECK-LABEL: @test10(
-; CHECK-NEXT:    [[CALL:%.*]] = tail call i8* @strndup(i8* dereferenceable(8) getelementptr inbounds ([8 x i8], [8 x i8]* @.str, i32 0, i32 0), i32 3) #0
+; CHECK-NEXT:    [[CALL:%.*]] = tail call dereferenceable_or_null(4) i8* @strndup(i8* dereferenceable(8) getelementptr inbounds ([8 x i8], [8 x i8]* @.str, i32 0, i32 0), i32 3) #0
 ; CHECK-NEXT:    store i8* [[CALL]], i8** [[ESC:%.*]], align 8
 ; CHECK-NEXT:    ret i32 4
 ;

Modified: llvm/trunk/test/Transforms/InstCombine/strndup.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/strndup.ll?rev=372647&r1=372646&r2=372647&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/strndup.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/strndup.ll Mon Sep 23 12:55:45 2019
@@ -18,7 +18,7 @@ define i8* @test1() {
 
 define i8* @test2() {
 ; CHECK-LABEL: @test2(
-; CHECK-NEXT:    [[RET:%.*]] = call i8* @strndup(i8* dereferenceable(6) getelementptr inbounds ([6 x i8], [6 x i8]* @hello, i64 0, i64 0), i32 4)
+; CHECK-NEXT:    [[RET:%.*]] = call dereferenceable_or_null(5) i8* @strndup(i8* dereferenceable(6) getelementptr inbounds ([6 x i8], [6 x i8]* @hello, i64 0, i64 0), i32 4)
 ; CHECK-NEXT:    ret i8* [[RET]]
 ;
   %src = getelementptr [6 x i8], [6 x i8]* @hello, i32 0, i32 0