[Attributor] Deduce "dereferenceable" attribute

Summary:
Deduce dereferenceable attribute in Attributor.

These will be added in a later patch.
* dereferenceable(_or_null)_globally (D61652)
* Deduction based on load instruction (similar to D64258)

Reviewers: jdoerfert, sstefan1

Reviewed By: jdoerfert

Subscribers: hiraditya, jfb, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D64876

llvm-svn: 366788

4 files changed, 66 insertions, 5 deletions

diff --git a/llvm/test/Transforms/FunctionAttrs/arg_nocapture.ll b/llvm/test/Transforms/FunctionAttrs/arg_nocapture.ll
index 0bc7053f7ad..eacc9fbe5f7 100644
--- a/llvm/test/Transforms/FunctionAttrs/arg_nocapture.ll
+++ b/llvm/test/Transforms/FunctionAttrs/arg_nocapture.ll
@@ -88,7 +88,7 @@ entry:
 ; Other arguments are possible here due to the no-return behavior.
 ;
 ; FIXME: no-return missing
-; CHECK: define noalias nonnull i32* @srec16(i32* nocapture readnone %a)
+; CHECK: define noalias nonnull dereferenceable(4294967295) i32* @srec16(i32* nocapture readnone %a)
 define i32* @srec16(i32* %a) #0 {
 entry:
   %call = call i32* @srec16(i32* %a)
diff --git a/llvm/test/Transforms/FunctionAttrs/dereferenceable.ll b/llvm/test/Transforms/FunctionAttrs/dereferenceable.ll
new file mode 100644
index 00000000000..16459fc4c42
--- /dev/null
+++ b/llvm/test/Transforms/FunctionAttrs/dereferenceable.ll
@@ -0,0 +1,52 @@
+; RUN: opt -attributor --attributor-disable=false -S < %s | FileCheck %s --check-prefixes=ATTRIBUTOR
+
+
+; TEST 1
+; take mininimum of return values
+;
+define i32* @test1(i32* dereferenceable(4), double* dereferenceable(8), i1 zeroext) local_unnamed_addr {
+; ATTRIBUTOR: define nonnull dereferenceable(4) i32* @test1(i32* nonnull dereferenceable(4), double* nonnull dereferenceable(8), i1 zeroext)
+  %4 = bitcast double* %1 to i32*
+  %5 = select i1 %2, i32* %0, i32* %4
+  ret i32* %5
+}
+
+; TEST 2
+define i32* @test2(i32* dereferenceable_or_null(4), double* dereferenceable(8), i1 zeroext) local_unnamed_addr {
+; ATTRIBUTOR: define dereferenceable_or_null(4) i32* @test2(i32* dereferenceable_or_null(4), double* nonnull dereferenceable(8), i1 zeroext)
+  %4 = bitcast double* %1 to i32*
+  %5 = select i1 %2, i32* %0, i32* %4
+  ret i32* %5
+}
+
+; TEST 3
+; GEP inbounds
+define i32* @test3_1(i32* dereferenceable(8)) local_unnamed_addr {
+; ATTRIBUTOR: define nonnull dereferenceable(4) i32* @test3_1(i32* nonnull dereferenceable(8))
+  %ret = getelementptr inbounds i32, i32* %0, i64 1
+  ret i32* %ret
+}
+
+define i32* @test3_2(i32* dereferenceable_or_null(32)) local_unnamed_addr {
+; FIXME: Argument should be mark dereferenceable because of GEP `inbounds`.
+; ATTRIBUTOR: define nonnull dereferenceable(16) i32* @test3_2(i32* dereferenceable_or_null(32))
+  %ret = getelementptr inbounds i32, i32* %0, i64 4
+  ret i32* %ret
+}
+
+define i32* @test3_3(i32* dereferenceable(8), i32* dereferenceable(16), i1) local_unnamed_addr {
+; ATTRIBUTOR: define nonnull dereferenceable(4) i32* @test3_3(i32* nonnull dereferenceable(8), i32* nonnull dereferenceable(16), i1) local_unnamed_addr
+  %ret1 = getelementptr inbounds i32, i32* %0, i64 1
+  %ret2 = getelementptr inbounds i32, i32* %1, i64 2
+  %ret = select i1 %2, i32* %ret1, i32* %ret2
+  ret i32* %ret
+}
+
+; TEST 4
+; Better than known in IR.
+
+define dereferenceable(4) i32* @test4(i32* dereferenceable(8)) local_unnamed_addr {
+; ATTRIBUTOR: define nonnull dereferenceable(8) i32* @test4(i32* nonnull returned dereferenceable(8))
+  ret i32* %0
+}
+
diff --git a/llvm/test/Transforms/FunctionAttrs/noalias_returned.ll b/llvm/test/Transforms/FunctionAttrs/noalias_returned.ll
index bd23ccb668b..989aa878f51 100644
--- a/llvm/test/Transforms/FunctionAttrs/noalias_returned.ll
+++ b/llvm/test/Transforms/FunctionAttrs/noalias_returned.ll
@@ -79,13 +79,13 @@ declare i8* @baz(...) nounwind uwtable
 ; TEST 5
 
 ; Returning global pointer. Should not be noalias.
-; CHECK: define nonnull i8** @getter()
+; CHECK: define nonnull dereferenceable(8) i8** @getter()
 define i8** @getter() {
   ret i8** @G
 }
 
 ; Returning global pointer. Should not be noalias.
-; CHECK: define nonnull i8** @calle1()
+; CHECK: define nonnull dereferenceable(8) i8** @calle1()
 define i8** @calle1(){
   %1 = call i8** @getter()
   ret i8** %1
diff --git a/llvm/test/Transforms/FunctionAttrs/nonnull.ll b/llvm/test/Transforms/FunctionAttrs/nonnull.ll
index 1ea14d034c8..cab72acb1a1 100644
--- a/llvm/test/Transforms/FunctionAttrs/nonnull.ll
+++ b/llvm/test/Transforms/FunctionAttrs/nonnull.ll
@@ -40,14 +40,14 @@ define i8* @test3() {
 ; just never return period.)
 define i8* @test4_helper() {
 ; FNATTR: define noalias nonnull i8* @test4_helper
-; ATTRIBUTOR: define noalias nonnull i8* @test4_helper
+; ATTRIBUTOR: define noalias nonnull dereferenceable(4294967295) i8* @test4_helper
   %ret = call i8* @test4()
   ret i8* %ret
 }
 
 define i8* @test4() {
 ; FNATTR: define noalias nonnull i8* @test4
-; ATTRIBUTOR: define noalias nonnull i8* @test4
+; ATTRIBUTOR: define noalias nonnull dereferenceable(4294967295) i8* @test4
   %ret = call i8* @test4_helper()
   ret i8* %ret
 }
@@ -219,6 +219,15 @@ bb:
   %tmp = call i32* @f1(i32* %arg)
   ret i32* null
 }
+
+; TEST 15
+define void @f15(i8* %arg) {
+; ATTRIBUTOR:   tail call void @use1(i8* nonnull dereferenceable(4) %arg)
+
+  tail call void @use1(i8* dereferenceable(4) %arg)
+  ret void
+}
+
 ; Test propagation of nonnull callsite args back to caller.
 
 declare void @use1(i8* %x)