Annotate return values of allocation functions with dereferenceable_or_null

Summary:
Example
define dso_local noalias i8* @_Z6maixxnv() local_unnamed_addr #0 {
entry:
  %call = tail call noalias dereferenceable_or_null(64) i8* @malloc(i64 64) #6
  ret i8* %call
}


Reviewers: jdoerfert

Reviewed By: jdoerfert

Subscribers: aaron.ballman, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D66651

llvm-svn: 370168

Author: davidbolvansky

llvm/include/llvm/Analysis/MemoryBuiltins.h

@@ -93,6 +93,11 @@ bool isReallocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
 /// reallocates memory (e.g., realloc).
 bool isReallocLikeFn(const Function *F, const TargetLibraryInfo *TLI);
 
+/// Tests if a value is a call or invoke to a library function that
+/// allocates memory and throws if an allocation failed (e.g., new).
+bool isOpNewLikeFn(const Value *V, const TargetLibraryInfo *TLI,
+                     bool LookThroughBitCast = false);
+
 //===----------------------------------------------------------------------===//
 //  malloc Call Utility Functions.
 //

llvm/lib/Analysis/MemoryBuiltins.cpp

@@ -276,6 +276,13 @@ bool llvm::isReallocLikeFn(const Function *F, const TargetLibraryInfo *TLI) {
   return getAllocationDataForFunction(F, ReallocLike, TLI).hasValue();
 }
 
+/// Tests if a value is a call or invoke to a library function that
+/// allocates memory and throws if an allocation failed (e.g., new).
+bool llvm::isOpNewLikeFn(const Value *V, const TargetLibraryInfo *TLI,
+                     bool LookThroughBitCast) {
+  return getAllocationData(V, OpNewLike, TLI, LookThroughBitCast).hasValue();
+}
+
 /// extractMallocCall - Returns the corresponding CallInst if the instruction
 /// is a malloc call.  Since CallInst::CreateMalloc() only creates calls, we
 /// ignore InvokeInst here.

llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp

@@ -4178,8 +4178,41 @@ static IntrinsicInst *findInitTrampoline(Value *Callee) {
   return nullptr;
 }
 
+static void annotateAnyAllocSite(CallBase &Call, const TargetLibraryInfo *TLI) {
+  ConstantInt *Op0C = dyn_cast<ConstantInt>(Call.getOperand(0));
+  ConstantInt *Op1C = (Call.getNumArgOperands() == 1)
+                          ? nullptr
+                          : dyn_cast<ConstantInt>(Call.getOperand(1));
+  if ((Op0C && Op0C->isNullValue()) || (Op1C && Op1C->isNullValue()))
+    return;
+  if (isMallocLikeFn(&Call, TLI) && Op0C) {
+    Call.addAttribute(AttributeList::ReturnIndex,
+                      Attribute::getWithDereferenceableOrNullBytes(
+                          Call.getContext(), Op0C->getZExtValue()));
+  } else if (isOpNewLikeFn(&Call, TLI) && Op0C) {
+    Call.addAttribute(AttributeList::ReturnIndex,
+                      Attribute::getWithDereferenceableBytes(
+                          Call.getContext(), Op0C->getZExtValue()));
+  } else if (isReallocLikeFn(&Call, TLI) && Op1C) {
+    Call.addAttribute(AttributeList::ReturnIndex,
+                      Attribute::getWithDereferenceableOrNullBytes(
+                          Call.getContext(), Op1C->getZExtValue()));
+  } else if (isCallocLikeFn(&Call, TLI) && Op0C && Op1C) {
+    bool Overflow;
+    const APInt &N = Op0C->getValue();
+    APInt Size = N.umul_ov(Op1C->getValue(), Overflow);
+    if (!Overflow)
+      Call.addAttribute(AttributeList::ReturnIndex,
+                        Attribute::getWithDereferenceableOrNullBytes(
+                            Call.getContext(), Size.getZExtValue()));
+  }
+}
+
 /// Improvements for call, callbr and invoke instructions.
 Instruction *InstCombiner::visitCallBase(CallBase &Call) {
+  if (isAllocationFn(&Call, &TLI))
+    annotateAnyAllocSite(Call, &TLI);
+
   if (isAllocLikeFn(&Call, &TLI))
     return visitAllocSite(Call);
 

llvm/test/Transforms/InstCombine/compare-unescaped.ll

@@ -1,27 +1,30 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
 ; RUN: opt -instcombine -S < %s | FileCheck %s
 
 @gp = global i32* null, align 8
 
 declare i8* @malloc(i64) #1
 
 define i1 @compare_global_trivialeq() {
+; CHECK-LABEL: @compare_global_trivialeq(
+; CHECK-NEXT:    ret i1 false
+;
   %m = call i8* @malloc(i64 4)
   %bc = bitcast i8* %m to i32*
   %lgp = load i32*, i32** @gp, align 8
   %cmp = icmp eq i32* %bc, %lgp
   ret i1 %cmp
-; CHECK-LABEL: compare_global_trivialeq
-; CHECK: ret i1 false
 }
 
 define i1 @compare_global_trivialne() {
+; CHECK-LABEL: @compare_global_trivialne(
+; CHECK-NEXT:    ret i1 true
+;
   %m = call i8* @malloc(i64 4)
   %bc = bitcast i8* %m to i32*
   %lgp = load i32*, i32** @gp, align 8
   %cmp = icmp ne i32* %bc, %lgp
   ret i1 %cmp
-; CHECK-LABEL: compare_global_trivialne
-; CHECK: ret i1 true
 }
 
 
@@ -30,102 +33,143 @@ define i1 @compare_global_trivialne() {
 ; The comparison should fold to false irrespective of whether the call to malloc can be elided or not
 declare void @f()
 define i1 @compare_and_call_with_deopt() {
-; CHECK-LABEL: compare_and_call_with_deopt
+; CHECK-LABEL: @compare_and_call_with_deopt(
+; CHECK-NEXT:    [[M:%.*]] = call dereferenceable_or_null(24) i8* @malloc(i64 24)
+; CHECK-NEXT:    tail call void @f() [ "deopt"(i8* [[M]]) ]
+; CHECK-NEXT:    ret i1 false
+;
   %m = call i8* @malloc(i64 24)
   %bc = bitcast i8* %m to i32*
   %lgp = load i32*, i32** @gp, align 8, !nonnull !0
   %cmp = icmp eq i32* %lgp, %bc
   tail call void @f() [ "deopt"(i8* %m) ]
   ret i1 %cmp
-; CHECK: ret i1 false
 }
 
 ; Same functon as above with deopt operand in function f, but comparison is NE
 define i1 @compare_ne_and_call_with_deopt() {
-; CHECK-LABEL: compare_ne_and_call_with_deopt
+; CHECK-LABEL: @compare_ne_and_call_with_deopt(
+; CHECK-NEXT:    [[M:%.*]] = call dereferenceable_or_null(24) i8* @malloc(i64 24)
+; CHECK-NEXT:    tail call void @f() [ "deopt"(i8* [[M]]) ]
+; CHECK-NEXT:    ret i1 true
+;
   %m = call i8* @malloc(i64 24)
   %bc = bitcast i8* %m to i32*
   %lgp = load i32*, i32** @gp, align 8, !nonnull !0
   %cmp = icmp ne i32* %lgp, %bc
   tail call void @f() [ "deopt"(i8* %m) ]
   ret i1 %cmp
-; CHECK: ret i1 true
 }
 
 ; Same function as above, but global not marked nonnull, and we cannot fold the comparison
 define i1 @compare_ne_global_maybe_null() {
-; CHECK-LABEL: compare_ne_global_maybe_null
+; CHECK-LABEL: @compare_ne_global_maybe_null(
+; CHECK-NEXT:    [[M:%.*]] = call dereferenceable_or_null(24) i8* @malloc(i64 24)
+; CHECK-NEXT:    [[BC:%.*]] = bitcast i8* [[M]] to i32*
+; CHECK-NEXT:    [[LGP:%.*]] = load i32*, i32** @gp, align 8
+; CHECK-NEXT:    [[CMP:%.*]] = icmp ne i32* [[LGP]], [[BC]]
+; CHECK-NEXT:    tail call void @f() [ "deopt"(i8* [[M]]) ]
+; CHECK-NEXT:    ret i1 [[CMP]]
+;
   %m = call i8* @malloc(i64 24)
   %bc = bitcast i8* %m to i32*
   %lgp = load i32*, i32** @gp
   %cmp = icmp ne i32* %lgp, %bc
   tail call void @f() [ "deopt"(i8* %m) ]
   ret i1 %cmp
-; CHECK: ret i1 %cmp
 }
 
 ; FIXME: The comparison should fold to false since %m escapes (call to function escape)
 ; after the comparison.
 declare void @escape(i8*)
 define i1 @compare_and_call_after() {
-; CHECK-LABEL: compare_and_call_after
+; CHECK-LABEL: @compare_and_call_after(
+; CHECK-NEXT:    [[M:%.*]] = call dereferenceable_or_null(24) i8* @malloc(i64 24)
+; CHECK-NEXT:    [[BC:%.*]] = bitcast i8* [[M]] to i32*
+; CHECK-NEXT:    [[LGP:%.*]] = load i32*, i32** @gp, align 8, !nonnull !0
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i32* [[LGP]], [[BC]]
+; CHECK-NEXT:    br i1 [[CMP]], label [[ESCAPE_CALL:%.*]], label [[JUST_RETURN:%.*]]
+; CHECK:       escape_call:
+; CHECK-NEXT:    call void @escape(i8* [[M]])
+; CHECK-NEXT:    ret i1 true
+; CHECK:       just_return:
+; CHECK-NEXT:    ret i1 [[CMP]]
+;
   %m = call i8* @malloc(i64 24)
   %bc = bitcast i8* %m to i32*
   %lgp = load i32*, i32** @gp, align 8, !nonnull !0
   %cmp = icmp eq i32* %bc, %lgp
   br i1 %cmp, label %escape_call, label %just_return
 
 escape_call:
- call void @escape(i8* %m)
- ret i1 true
+  call void @escape(i8* %m)
+  ret i1 true
 
 just_return:
- ret i1 %cmp
+  ret i1 %cmp
 }
 
 define i1 @compare_distinct_mallocs() {
+; CHECK-LABEL: @compare_distinct_mallocs(
+; CHECK-NEXT:    ret i1 false
+;
   %m = call i8* @malloc(i64 4)
   %n = call i8* @malloc(i64 4)
   %cmp = icmp eq i8* %m, %n
   ret i1 %cmp
-  ; CHECK-LABEL: compare_distinct_mallocs
-  ; CHECK: ret i1 false
 }
 
-; the compare is folded to true since the folding compare looks through bitcasts. 
-; call to malloc and the bitcast instructions are elided after that since there are no uses of the malloc 
+; the compare is folded to true since the folding compare looks through bitcasts.
+; call to malloc and the bitcast instructions are elided after that since there are no uses of the malloc
 define i1 @compare_samepointer_under_bitcast() {
+; CHECK-LABEL: @compare_samepointer_under_bitcast(
+; CHECK-NEXT:    ret i1 true
+;
   %m = call i8* @malloc(i64 4)
   %bc = bitcast i8* %m to i32*
   %bcback = bitcast i32* %bc to i8*
   %cmp = icmp eq i8* %m, %bcback
   ret i1 %cmp
-; CHECK-LABEL: compare_samepointer_under_bitcast
-; CHECK: ret i1 true 
 }
 
-; the compare is folded to true since the folding compare looks through bitcasts. 
+; the compare is folded to true since the folding compare looks through bitcasts.
 ; The malloc call for %m cannot be elided since it is used in the call to function f.
 define i1 @compare_samepointer_escaped() {
+; CHECK-LABEL: @compare_samepointer_escaped(
+; CHECK-NEXT:    [[M:%.*]] = call dereferenceable_or_null(4) i8* @malloc(i64 4)
+; CHECK-NEXT:    call void @f() [ "deopt"(i8* [[M]]) ]
+; CHECK-NEXT:    ret i1 true
+;
   %m = call i8* @malloc(i64 4)
   %bc = bitcast i8* %m to i32*
   %bcback = bitcast i32* %bc to i8*
   %cmp = icmp eq i8* %m, %bcback
   call void @f() [ "deopt"(i8* %m) ]
   ret i1 %cmp
-; CHECK-LABEL: compare_samepointer_escaped
-; CHECK-NEXT: %m = call i8* @malloc(i64 4)
-; CHECK-NEXT: call void @f() [ "deopt"(i8* %m) ]
-; CHECK: ret i1 true 
 }
 
 ; Technically, we can fold the %cmp2 comparison, even though %m escapes through
 ; the ret statement since `ret` terminates the function and we cannot reach from
-; the ret to cmp. 
+; the ret to cmp.
 ; FIXME: Folding this %cmp2 when %m escapes through ret could be an issue with
 ; cross-threading data dependencies since we do not make the distinction between
 ; atomic and non-atomic loads in capture tracking.
 define i8* @compare_ret_escape(i8* %c) {
+; CHECK-LABEL: @compare_ret_escape(
+; CHECK-NEXT:    [[M:%.*]] = call dereferenceable_or_null(4) i8* @malloc(i64 4)
+; CHECK-NEXT:    [[N:%.*]] = call dereferenceable_or_null(4) i8* @malloc(i64 4)
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq i8* [[N]], [[C:%.*]]
+; CHECK-NEXT:    br i1 [[CMP]], label [[RETST:%.*]], label [[CHK:%.*]]
+; CHECK:       retst:
+; CHECK-NEXT:    ret i8* [[M]]
+; CHECK:       chk:
+; CHECK-NEXT:    [[BC:%.*]] = bitcast i8* [[M]] to i32*
+; CHECK-NEXT:    [[LGP:%.*]] = load i32*, i32** @gp, align 8, !nonnull !0
+; CHECK-NEXT:    [[CMP2:%.*]] = icmp eq i32* [[LGP]], [[BC]]
+; CHECK-NEXT:    br i1 [[CMP2]], label [[RETST]], label [[CHK2:%.*]]
+; CHECK:       chk2:
+; CHECK-NEXT:    ret i8* [[N]]
+;
   %m = call i8* @malloc(i64 4)
   %n = call i8* @malloc(i64 4)
   %cmp = icmp eq i8* %n, %c
@@ -142,23 +186,21 @@ chk:
 
 chk2:
   ret i8* %n
-; CHECK-LABEL: compare_ret_escape
-; CHECK: %cmp = icmp eq i8* %n, %c
-; CHECK: %cmp2 = icmp eq i32* %lgp, %bc
 }
 
 ; The malloc call for %m cannot be elided since it is used in the call to function f.
 ; However, the cmp can be folded to true as %n doesnt escape and %m, %n are distinct allocations
 define i1 @compare_distinct_pointer_escape() {
+; CHECK-LABEL: @compare_distinct_pointer_escape(
+; CHECK-NEXT:    [[M:%.*]] = call dereferenceable_or_null(4) i8* @malloc(i64 4)
+; CHECK-NEXT:    tail call void @f() [ "deopt"(i8* [[M]]) ]
+; CHECK-NEXT:    ret i1 true
+;
   %m = call i8* @malloc(i64 4)
   %n = call i8* @malloc(i64 4)
   tail call void @f() [ "deopt"(i8* %m) ]
   %cmp = icmp ne i8* %m, %n
   ret i1 %cmp
-; CHECK-LABEL: compare_distinct_pointer_escape
-; CHECK-NEXT: %m = call i8* @malloc(i64 4)
-; CHECK-NEXT: tail call void @f() [ "deopt"(i8* %m) ]
-; CHECK-NEXT: ret i1 true
 }
 
 !0 = !{}

llvm/test/Transforms/InstCombine/deref-alloc-fns.ll

@@ -17,7 +17,7 @@ define noalias i8* @malloc_nonconstant_size(i64 %n) {
 
 define noalias i8* @malloc_constant_size() {
 ; CHECK-LABEL: @malloc_constant_size(
-; CHECK-NEXT:    [[CALL:%.*]] = tail call noalias i8* @malloc(i64 40)
+; CHECK-NEXT:    [[CALL:%.*]] = tail call noalias dereferenceable_or_null(40) i8* @malloc(i64 40)
 ; CHECK-NEXT:    ret i8* [[CALL]]
 ;
   %call = tail call noalias i8* @malloc(i64 40)
@@ -35,7 +35,7 @@ define noalias i8* @malloc_constant_size2() {
 
 define noalias i8* @malloc_constant_size3() {
 ; CHECK-LABEL: @malloc_constant_size3(
-; CHECK-NEXT:    [[CALL:%.*]] = tail call noalias dereferenceable(80) i8* @malloc(i64 40)
+; CHECK-NEXT:    [[CALL:%.*]] = tail call noalias dereferenceable(80) dereferenceable_or_null(40) i8* @malloc(i64 40)
 ; CHECK-NEXT:    ret i8* [[CALL]]
 ;
   %call = tail call noalias dereferenceable(80) i8* @malloc(i64 40)
@@ -72,7 +72,7 @@ define noalias i8* @realloc_constant_zero_size(i8* %p) {
 
 define noalias i8* @realloc_constant_size(i8* %p) {
 ; CHECK-LABEL: @realloc_constant_size(
-; CHECK-NEXT:    [[CALL:%.*]] = tail call noalias i8* @realloc(i8* [[P:%.*]], i64 40)
+; CHECK-NEXT:    [[CALL:%.*]] = tail call noalias dereferenceable_or_null(40) i8* @realloc(i8* [[P:%.*]], i64 40)
 ; CHECK-NEXT:    ret i8* [[CALL]]
 ;
   %call = tail call noalias i8* @realloc(i8* %p, i64 40)
@@ -136,7 +136,7 @@ define noalias i8* @calloc_constant_zero_size3(i64 %n) {
 
 define noalias i8* @calloc_constant_size() {
 ; CHECK-LABEL: @calloc_constant_size(
-; CHECK-NEXT:    [[CALL:%.*]] = tail call noalias i8* @calloc(i64 16, i64 8)
+; CHECK-NEXT:    [[CALL:%.*]] = tail call noalias dereferenceable_or_null(128) i8* @calloc(i64 16, i64 8)
 ; CHECK-NEXT:    ret i8* [[CALL]]
 ;
   %call = tail call noalias i8* @calloc(i64 16, i64 8)
@@ -152,7 +152,6 @@ define noalias i8* @calloc_constant_size_overflow() {
   ret i8* %call
 }
 
-
 define noalias i8* @op_new_nonconstant_size(i64 %n) {
 ; CHECK-LABEL: @op_new_nonconstant_size(
 ; CHECK-NEXT:    [[CALL:%.*]] = tail call i8* @_Znam(i64 [[N:%.*]])
@@ -162,17 +161,17 @@ define noalias i8* @op_new_nonconstant_size(i64 %n) {
   ret i8* %call
 }
 
-define noalias i8* @op_new_constant_zero_size() {
-; CHECK-LABEL: @op_new_constant_zero_size(
-; CHECK-NEXT:    [[CALL:%.*]] = tail call i8* @_Znam(i64 40)
+define noalias i8* @op_new_constant_size() {
+; CHECK-LABEL: @op_new_constant_size(
+; CHECK-NEXT:    [[CALL:%.*]] = tail call dereferenceable_or_null(40) i8* @_Znam(i64 40)
 ; CHECK-NEXT:    ret i8* [[CALL]]
 ;
   %call = tail call i8* @_Znam(i64 40)
   ret i8* %call
 }
 
-define noalias i8* @op_new_constant_size() {
-; CHECK-LABEL: @op_new_constant_size(
+define noalias i8* @op_new_constant_zero_size() {
+; CHECK-LABEL: @op_new_constant_zero_size(
 ; CHECK-NEXT:    [[CALL:%.*]] = tail call i8* @_Znam(i64 0)
 ; CHECK-NEXT:    ret i8* [[CALL]]
 ;