[Attributor] Add "free"-based heap2stack deduction

Summary:
If there is a unique free of the allocated that has to be reached from
the malloc, we can apply the heap-2-stack transformation even if the
pointer escapes.

Reviewers: hfinkel, sstefan1, uenoku

Subscribers: hiraditya, bollu, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D68958

2 files changed, 34 insertions, 14 deletions

diff --git a/llvm/test/Transforms/FunctionAttrs/heap_to_stack.ll b/llvm/test/Transforms/FunctionAttrs/heap_to_stack.ll
index 876760a8051..04313cf0e77 100644
--- a/llvm/test/Transforms/FunctionAttrs/heap_to_stack.ll
+++ b/llvm/test/Transforms/FunctionAttrs/heap_to_stack.ll
@@ -8,7 +8,7 @@ declare void @func_throws(...)
 
 declare void @sync_func(i8* %p)
 
-declare void @sync_will_return(i8* %p) willreturn
+declare void @sync_will_return(i8* %p) willreturn nounwind
 
 declare void @no_sync_func(i8* nocapture %p) nofree nosync willreturn
 
@@ -202,11 +202,11 @@ define i32 @test_lifetime() {
 }
 
 ; TEST 11 
-; FIXME: should be ok
 
 define void @test11() {
   %1 = tail call noalias i8* @malloc(i64 4)
-  ; CHECK: @malloc(i64 4)
+  ; CHECK: test11
+  ; CHECK-NEXT: alloc
   ; CHECK-NEXT: @sync_will_return(i8* %1)
   tail call void @sync_will_return(i8* %1)
   tail call void @free(i8* %1)
@@ -330,9 +330,29 @@ define void @test16b(i8 %v, i8** %P) {
   %1 = tail call noalias i8* @malloc(i64 4)
   ; CHECK-NEXT: store i8* %1, i8** %P
   store i8* %1, i8** %P
-  ; CHECK-NEXT: @no_sync_func(i8* %1)
+  ; CHECK-NEXT: @no_sync_func(i8* nocapture %1)
   tail call void @no_sync_func(i8* %1)
   ; CHECK-NEXT: @free(i8* %1)
   tail call void @free(i8* %1)
   ret void
 }
+
+define void @test16c(i8 %v, i8** %P) {
+  ; CHECK: %1 = alloca
+  %1 = tail call noalias i8* @malloc(i64 4)
+  ; CHECK-NEXT: store i8* %1, i8** %P
+  store i8* %1, i8** %P
+  ; CHECK-NEXT: @no_sync_func(i8* nocapture %1)
+  tail call void @no_sync_func(i8* %1) nounwind
+  ; CHECK-NOT: @free
+  tail call void @free(i8* %1)
+  ret void
+}
+
+define void @test16d(i8 %v, i8** %P) {
+  ; CHECK: %1 = tail call noalias i8* @malloc(i64 4)
+  %1 = tail call noalias i8* @malloc(i64 4)
+  ; CHECK-NEXT: store i8* %1, i8** %P
+  store i8* %1, i8** %P
+  ret void
+}
diff --git a/llvm/test/Transforms/FunctionAttrs/noalias_returned.ll b/llvm/test/Transforms/FunctionAttrs/noalias_returned.ll
index 72de6fb282b..8cb1ec2eb4e 100644
--- a/llvm/test/Transforms/FunctionAttrs/noalias_returned.ll
+++ b/llvm/test/Transforms/FunctionAttrs/noalias_returned.ll
@@ -204,7 +204,7 @@ define void @test12_1() {
 ; CHECK-NEXT:    tail call void @use_nocapture(i8* noalias nonnull align 4 dereferenceable(1) [[A]])
 ; CHECK-NEXT:    tail call void @use_nocapture(i8* noalias nonnull align 4 dereferenceable(1) [[A]])
 ; CHECK-NEXT:    tail call void @use_nocapture(i8* noalias nocapture [[B]])
-; CHECK-NEXT:    tail call void @use_nocapture(i8* noalias [[B]])
+; CHECK-NEXT:    tail call void @use_nocapture(i8* noalias nocapture [[B]])
 ; CHECK-NEXT:    ret void
 ;
   %A = alloca i8, align 4
@@ -221,10 +221,10 @@ define void @test12_2(){
 ; CHECK-NEXT:    [[A:%.*]] = tail call noalias i8* @malloc(i64 4)
 ; FIXME: This should be @use_nocapture(i8* noalias [[A]])
 ; CHECK-NEXT:    tail call void @use_nocapture(i8* nocapture [[A]])
-; FIXME: This should be @use_nocapture(i8* noalias [[A]])
-; CHECK-NEXT:    tail call void @use_nocapture(i8* [[A]])
+; FIXME: This should be @use_nocapture(i8* noalias nocapture [[A]])
+; CHECK-NEXT:    tail call void @use_nocapture(i8* nocapture [[A]])
 ; CHECK-NEXT:    tail call void @use(i8* [[A]])
-; CHECK-NEXT:    tail call void @use_nocapture(i8* [[A]])
+; CHECK-NEXT:    tail call void @use_nocapture(i8* nocapture [[A]])
 ; CHECK-NEXT:    ret void
 ;
   %A = tail call noalias i8* @malloc(i64 4)
@@ -239,7 +239,7 @@ declare void @two_args(i8* nocapture , i8* nocapture)
 define void @test12_3(){
 ; CHECK-LABEL: @test12_3(
   %A = tail call noalias i8* @malloc(i64 4)
-; CHECK: tail call void @two_args(i8* nocapture %A, i8* %A)
+; CHECK: tail call void @two_args(i8* nocapture %A, i8* nocapture %A)
   tail call void @two_args(i8* %A, i8* %A)
   ret void
 }
@@ -252,17 +252,17 @@ define void @test12_4(){
   %A_1 = getelementptr i8, i8* %A, i64 1
   %B_0 = getelementptr i8, i8* %B, i64 0
 
-; CHECK: tail call void @two_args(i8* noalias %A, i8* noalias %B)
+; CHECK: tail call void @two_args(i8* noalias nocapture %A, i8* noalias nocapture %B)
   tail call void @two_args(i8* %A, i8* %B)
 
-; CHECK: tail call void @two_args(i8* %A, i8* nocapture %A_0)
+; CHECK: tail call void @two_args(i8* nocapture %A, i8* nocapture %A_0)
   tail call void @two_args(i8* %A, i8* %A_0)
 
-; CHECK: tail call void @two_args(i8* %A, i8* %A_1)
+; CHECK: tail call void @two_args(i8* nocapture %A, i8* nocapture %A_1)
   tail call void @two_args(i8* %A, i8* %A_1)
 
-; FIXME: This should be @two_args(i8* noalias %A_0, i8* noalias %B_0)
-; CHECK: tail call void @two_args(i8* %A_0, i8* nocapture %B_0)
+; FIXME: This should be @two_args(i8* noalias nocapture %A_0, i8* noalias nocapture %B_0)
+; CHECK: tail call void @two_args(i8* nocapture %A_0, i8* nocapture %B_0)
   tail call void @two_args(i8* %A_0, i8* %B_0)
   ret void
 }