[Coroutines] Part14: Handle coroutines with no suspend points.

Summary:
If coroutine has no suspend points, remove heap allocation and turn a coroutine into a normal function.

Also, if a pattern is detected that coroutine resumes or destroys itself prior to coro.suspend call, turn the suspend point into a simple jump to resume or cleanup label. This pattern occurs when coroutines are used to propagate errors in functions that return expected<T>.

Reviewers: majnemer

Subscribers: mehdi_amini, llvm-commits

Differential Revision: https://reviews.llvm.org/D24408

llvm-svn: 282414

1 files changed, 189 insertions, 0 deletions

diff --git a/llvm/test/Transforms/Coroutines/no-suspend.ll b/llvm/test/Transforms/Coroutines/no-suspend.ll
new file mode 100644
index 00000000000..d219495de6c
--- /dev/null
+++ b/llvm/test/Transforms/Coroutines/no-suspend.ll
@@ -0,0 +1,189 @@
+; Test no suspend coroutines
+; RUN: opt < %s -O2 -enable-coroutines -S | FileCheck %s
+
+; Coroutine with no-suspends will turn into:
+;
+; CHECK-LABEL: define void @no_suspends(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    call void @print(i32 %n)
+; CHECK-NEXT:    ret void
+;
+define void @no_suspends(i32 %n) {
+entry:
+  %id = call token @llvm.coro.id(i32 0, i8* null, i8* null, i8* null)
+  %need.dyn.alloc = call i1 @llvm.coro.alloc(token %id)
+  br i1 %need.dyn.alloc, label %dyn.alloc, label %coro.begin
+dyn.alloc:
+  %size = call i32 @llvm.coro.size.i32()
+  %alloc = call i8* @malloc(i32 %size)
+  br label %coro.begin
+coro.begin:
+  %phi = phi i8* [ null, %entry ], [ %alloc, %dyn.alloc ]
+  %hdl = call noalias i8* @llvm.coro.begin(token %id, i8* %phi)
+  br label %body
+body:
+  call void @print(i32 %n)
+  br label %cleanup
+cleanup:
+  %mem = call i8* @llvm.coro.free(token %id, i8* %hdl)
+  %need.dyn.free = icmp ne i8* %mem, null
+  br i1 %need.dyn.free, label %dyn.free, label %suspend
+dyn.free:
+  call void @free(i8* %mem)
+  br label %suspend
+suspend:
+  call void @llvm.coro.end(i8* %hdl, i1 false)
+  ret void
+}
+
+; SimplifySuspendPoint will detect that coro.resume resumes itself and will
+; replace suspend with a jump to %resume label turning it into no-suspend 
+; coroutine.
+;
+; CHECK-LABEL: define void @simplify_resume(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    call void @print(i32 0)
+; CHECK-NEXT:    ret void
+;
+define void @simplify_resume() {
+entry:
+  %id = call token @llvm.coro.id(i32 0, i8* null, i8* null, i8* null)
+  %need.dyn.alloc = call i1 @llvm.coro.alloc(token %id)
+  br i1 %need.dyn.alloc, label %dyn.alloc, label %coro.begin
+dyn.alloc:
+  %size = call i32 @llvm.coro.size.i32()
+  %alloc = call i8* @malloc(i32 %size)
+  br label %coro.begin
+coro.begin:
+  %phi = phi i8* [ null, %entry ], [ %alloc, %dyn.alloc ]
+  %hdl = call noalias i8* @llvm.coro.begin(token %id, i8* %phi)
+  br label %body
+body:
+  %save = call token @llvm.coro.save(i8* %hdl)
+  call void @llvm.coro.resume(i8* %hdl)
+  %0 = call i8 @llvm.coro.suspend(token %save, i1 false)
+  switch i8 %0, label %suspend [i8 0, label %resume
+                                i8 1, label %pre.cleanup]
+resume:
+  call void @print(i32 0)
+  br label %cleanup
+
+pre.cleanup:
+  call void @print(i32 1)
+  br label %cleanup
+
+cleanup:
+  %mem = call i8* @llvm.coro.free(token %id, i8* %hdl)
+  call void @free(i8* %mem)
+  br label %suspend
+suspend:
+  call void @llvm.coro.end(i8* %hdl, i1 false)
+  ret void
+}
+
+; SimplifySuspendPoint will detect that coroutine destroys itself and will
+; replace suspend with a jump to %cleanup label turning it into no-suspend 
+; coroutine.
+;
+; CHECK-LABEL: define void @simplify_destroy(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    call void @print(i32 1)
+; CHECK-NEXT:    ret void
+;
+define void @simplify_destroy() {
+entry:
+  %id = call token @llvm.coro.id(i32 0, i8* null, i8* null, i8* null)
+  %need.dyn.alloc = call i1 @llvm.coro.alloc(token %id)
+  br i1 %need.dyn.alloc, label %dyn.alloc, label %coro.begin
+dyn.alloc:
+  %size = call i32 @llvm.coro.size.i32()
+  %alloc = call i8* @malloc(i32 %size)
+  br label %coro.begin
+coro.begin:
+  %phi = phi i8* [ null, %entry ], [ %alloc, %dyn.alloc ]
+  %hdl = call noalias i8* @llvm.coro.begin(token %id, i8* %phi)
+  br label %body
+body:
+  %save = call token @llvm.coro.save(i8* %hdl)
+  call void @llvm.coro.destroy(i8* %hdl)
+  %0 = call i8 @llvm.coro.suspend(token %save, i1 false)
+  switch i8 %0, label %suspend [i8 0, label %resume
+                                i8 1, label %pre.cleanup]
+resume:
+  call void @print(i32 0)
+  br label %cleanup
+
+pre.cleanup:
+  call void @print(i32 1)
+  br label %cleanup
+
+cleanup:
+  %mem = call i8* @llvm.coro.free(token %id, i8* %hdl)
+  call void @free(i8* %mem)
+  br label %suspend
+suspend:
+  call void @llvm.coro.end(i8* %hdl, i1 false)
+  ret void
+}
+
+; SimplifySuspendPoint won't be able to simplify if it detects that there are
+; other calls between coro.save and coro.suspend. They potentially can call
+; resume or destroy, so we should not simplify this suspend point.
+;
+; CHECK-LABEL: define void @cannot_simplify(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    call i8* @malloc
+
+define void @cannot_simplify() {
+entry:
+  %id = call token @llvm.coro.id(i32 0, i8* null, i8* null, i8* null)
+  %need.dyn.alloc = call i1 @llvm.coro.alloc(token %id)
+  br i1 %need.dyn.alloc, label %dyn.alloc, label %coro.begin
+dyn.alloc:
+  %size = call i32 @llvm.coro.size.i32()
+  %alloc = call i8* @malloc(i32 %size)
+  br label %coro.begin
+coro.begin:
+  %phi = phi i8* [ null, %entry ], [ %alloc, %dyn.alloc ]
+  %hdl = call noalias i8* @llvm.coro.begin(token %id, i8* %phi)
+  br label %body
+body:
+  %save = call token @llvm.coro.save(i8* %hdl)
+  call void @foo()
+  call void @llvm.coro.destroy(i8* %hdl)
+  %0 = call i8 @llvm.coro.suspend(token %save, i1 false)
+  switch i8 %0, label %suspend [i8 0, label %resume
+                                i8 1, label %pre.cleanup]
+resume:
+  call void @print(i32 0)
+  br label %cleanup
+
+pre.cleanup:
+  call void @print(i32 1)
+  br label %cleanup
+
+cleanup:
+  %mem = call i8* @llvm.coro.free(token %id, i8* %hdl)
+  call void @free(i8* %mem)
+  br label %suspend
+suspend:
+  call void @llvm.coro.end(i8* %hdl, i1 false)
+  ret void
+}
+
+declare i8* @malloc(i32)
+declare void @free(i8*)
+declare void @print(i32)
+declare void @foo()
+
+declare token @llvm.coro.id(i32, i8*, i8*, i8*)
+declare i1 @llvm.coro.alloc(token)
+declare i32 @llvm.coro.size.i32()
+declare i8* @llvm.coro.begin(token, i8*)
+declare token @llvm.coro.save(i8* %hdl)
+declare i8 @llvm.coro.suspend(token, i1)
+declare i8* @llvm.coro.free(token, i8*)
+declare void @llvm.coro.end(i8*, i1)
+
+declare void @llvm.coro.resume(i8*)
+declare void @llvm.coro.destroy(i8*)