[IR] Reformulate LLVM's EH funclet IR
While we have successfully implemented a funclet-oriented EH scheme on
top of LLVM IR, our scheme has some notable deficiencies:
- catchendpad and cleanupendpad are necessary in the current design
but they are difficult to explain to others, even to seasoned LLVM
experts.
- catchendpad and cleanupendpad are optimization barriers. They cannot
be split and force all potentially throwing call-sites to be invokes.
This has a noticable effect on the quality of our code generation.
- catchpad, while similar in some aspects to invoke, is fairly awkward.
It is unsplittable, starts a funclet, and has control flow to other
funclets.
- The nesting relationship between funclets is currently a property of
control flow edges. Because of this, we are forced to carefully
analyze the flow graph to see if there might potentially exist illegal
nesting among funclets. While we have logic to clone funclets when
they are illegally nested, it would be nicer if we had a
representation which forbade them upfront.
Let's clean this up a bit by doing the following:
- Instead, make catchpad more like cleanuppad and landingpad: no control
flow, just a bunch of simple operands; catchpad would be splittable.
- Introduce catchswitch, a control flow instruction designed to model
the constraints of funclet oriented EH.
- Make funclet scoping explicit by having funclet instructions consume
the token produced by the funclet which contains them.
- Remove catchendpad and cleanupendpad. Their presence can be inferred
implicitly using coloring information.
N.B. The state numbering code for the CLR has been updated but the
veracity of it's output cannot be spoken for. An expert should take a
look to make sure the results are reasonable.
Reviewers: rnk, JosephTremoulet, andrew.w.kaylor
Differential Revision: http://reviews.llvm.org/D15139
llvm-svn: 255422
2015-12-12 13:38:55 +08:00
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; RUN: sed -e s/.T1:// %s | not llvm-as -disable-output 2>&1 | FileCheck --check-prefix=CHECK1 %s
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; RUN: sed -e s/.T2:// %s | not llvm-as -disable-output 2>&1 | FileCheck --check-prefix=CHECK2 %s
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; RUN: sed -e s/.T3:// %s | not llvm-as -disable-output 2>&1 | FileCheck --check-prefix=CHECK3 %s
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; RUN: sed -e s/.T4:// %s | not llvm-as -disable-output 2>&1 | FileCheck --check-prefix=CHECK4 %s
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2016-01-02 23:24:24 +08:00
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; RUN: sed -e s/.T5:// %s | not opt -verify -disable-output 2>&1 | FileCheck --check-prefix=CHECK5 %s
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; RUN: sed -e s/.T6:// %s | not opt -verify -disable-output 2>&1 | FileCheck --check-prefix=CHECK6 %s
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; RUN: sed -e s/.T7:// %s | not opt -verify -disable-output 2>&1 | FileCheck --check-prefix=CHECK7 %s
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declare void @g()
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[IR] Reformulate LLVM's EH funclet IR
While we have successfully implemented a funclet-oriented EH scheme on
top of LLVM IR, our scheme has some notable deficiencies:
- catchendpad and cleanupendpad are necessary in the current design
but they are difficult to explain to others, even to seasoned LLVM
experts.
- catchendpad and cleanupendpad are optimization barriers. They cannot
be split and force all potentially throwing call-sites to be invokes.
This has a noticable effect on the quality of our code generation.
- catchpad, while similar in some aspects to invoke, is fairly awkward.
It is unsplittable, starts a funclet, and has control flow to other
funclets.
- The nesting relationship between funclets is currently a property of
control flow edges. Because of this, we are forced to carefully
analyze the flow graph to see if there might potentially exist illegal
nesting among funclets. While we have logic to clone funclets when
they are illegally nested, it would be nicer if we had a
representation which forbade them upfront.
Let's clean this up a bit by doing the following:
- Instead, make catchpad more like cleanuppad and landingpad: no control
flow, just a bunch of simple operands; catchpad would be splittable.
- Introduce catchswitch, a control flow instruction designed to model
the constraints of funclet oriented EH.
- Make funclet scoping explicit by having funclet instructions consume
the token produced by the funclet which contains them.
- Remove catchendpad and cleanupendpad. Their presence can be inferred
implicitly using coloring information.
N.B. The state numbering code for the CLR has been updated but the
veracity of it's output cannot be spoken for. An expert should take a
look to make sure the results are reasonable.
Reviewers: rnk, JosephTremoulet, andrew.w.kaylor
Differential Revision: http://reviews.llvm.org/D15139
llvm-svn: 255422
2015-12-12 13:38:55 +08:00
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;T1: define void @f() {
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;T1: entry:
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;T1: catchret from undef to label %next
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;T1: ; CHECK1: CatchReturnInst needs to be provided a CatchPad
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;T1: next:
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;T1: unreachable
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;T1: }
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;T2: define void @f() {
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;T2: entry:
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;T2: %x = cleanuppad within none []
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;T2: ; catchret's first operand's operator must be catchpad
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;T2: catchret from %x to label %entry
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;T2: ; CHECK2: CatchReturnInst needs to be provided a CatchPad
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;T2: }
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;T3: define void @f() {
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;T3: entry:
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;T3: cleanupret from undef unwind label %next
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;T3: ; CHECK3: CleanupReturnInst needs to be provided a CleanupPad
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;T3: next:
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;T3: unreachable
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;T3: }
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;T4: define void @f() {
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;T4: entry:
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;T4: %cs = catchswitch within none [label %next] unwind to caller
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;T4: next:
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;T4: %x = catchpad within %cs []
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;T4: ; cleanupret first operand's operator must be cleanuppad
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;T4: cleanupret from %x unwind to caller
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;T4: ; CHECK4: CleanupReturnInst needs to be provided a CleanupPad
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;T4: }
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2016-01-02 23:24:24 +08:00
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;T5: define void @f() personality void ()* @g {
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;T5: entry:
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;T5: ret void
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;T5: switch:
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;T5: %cs = catchswitch within none [label %catch] unwind to caller
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;T5: catch:
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;T5: catchpad within %cs []
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;T5: unreachable
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;T5: bogus:
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;T5: cleanuppad within %cs []
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;T5: ; CHECK5: CleanupPadInst has an invalid parent
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;T5: unreachable
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;T5: }
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;T6: define void @f() personality void ()* @g {
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;T6: entry:
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;T6: ret void
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;T6: switch1:
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;T6: %cs1 = catchswitch within none [label %catch1] unwind label %catch2
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;T6: ; CHECK6: Block containg CatchPadInst must be jumped to only by its catchswitch
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;T6: catch1:
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;T6: catchpad within %cs1 []
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;T6: unreachable
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;T6: switch2:
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;T6: %cs2 = catchswitch within none [label %catch2] unwind to caller
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;T6: catch2:
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;T6: catchpad within %cs2 []
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;T6: unreachable
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;T6: }
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;T7: define void @f() personality void ()* @g {
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;T7: entry:
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;T7: ret void
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;T7: switch1:
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;T7: %cs1 = catchswitch within none [label %catch1] unwind to caller
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;T7: catch1:
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;T7: catchpad within %cs1 []
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;T7: unreachable
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;T7: switch2:
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;T7: %cs2 = catchswitch within %cs1 [label %catch2] unwind to caller
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;T7: ; CHECK7: CatchSwitchInst has an invalid parent
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;T7: catch2:
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;T7: catchpad within %cs2 []
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;T7: unreachable
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;T7: }
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