1518b260ce
Clang's `-fwhole-program-vtables` is required for this optimization to
take place. If `-fwhole-program-vtables` is not enabled, this change is
no-op.
* Function-comparison (before):
```
%vtable = load ptr, ptr %obj
%vfn = getelementptr inbounds ptr, ptr %vtable, i64 1
%func = load ptr, ptr %vfn
%cond = icmp eq ptr %func, @callee
br i1 %cond, label bb1, label bb2:
bb1:
call @callee
bb2:
call %func
```
* VTable-comparison (after):
```
%vtable = load ptr, ptr %obj
%cond = icmp eq ptr %vtable, @vtable-address-point
br i1 %cond, label bb1, label bb2:
bb1:
call @callee
bb2:
%vfn = getelementptr inbounds ptr, ptr %vtable, i64 1
%func = load ptr, ptr %vfn
call %func
```
Key changes:
1. Find out virtual calls and the vtables they come from.
- The ICP relies on type intrinsic `llvm.type.test` to find out virtual
calls and the
compatible vtables, and relies on type metadata to find the address
point for comparison.
2. ICP pass does cost-benefit analysis and compares vtable only when the
number of vtables for a function candidate is within (option specified)
threshold.
3. Sink the function addressing and vtable load instruction to indirect
fallback.
- The sink helper functions are simplified versions of
`InstCombinerImpl::tryToSinkInstruction`. Currently debug intrinsics are
not handled. Ideally `InstCombinerImpl::tryToSinkInstructionDbgValues`
and `InstCombinerImpl::tryToSinkInstructionDbgVariableRecords` could be
moved into Transforms/Utils/Local.cpp (or another util cpp file) to
handle debug intrinsics when moving instructions across basic blocks.
4. Keep value profiles updated
1) Update vtable value profiles after inline
2) For either function-based comparison or vtable-based comparison,
update both vtable and indirect call value profiles.
101 lines
4.0 KiB
LLVM
101 lines
4.0 KiB
LLVM
; Tests that instructions with value profiles and count-type branch weights are
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; updated in both caller and callee after inline, but invoke instructions with
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; taken or not taken branch probabilities are not updated.
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; RUN: opt < %s -passes='require<profile-summary>,cgscc(inline)' -S | FileCheck %s
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declare i32 @__gxx_personality_v0(...)
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define void @caller(ptr %func) personality ptr @__gxx_personality_v0 !prof !15 {
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call void @callee(ptr %func), !prof !16
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ret void
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}
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declare void @callee1(ptr %func)
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declare void @callee2(ptr %func)
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define void @callee(ptr %obj) personality ptr @__gxx_personality_v0 !prof !17 {
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%vtable = load ptr, ptr %obj, !prof !21
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%func = load ptr, ptr %vtable
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invoke void %func()
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to label %next unwind label %lpad, !prof !18
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next:
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invoke void @callee1(ptr %func)
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to label %cont unwind label %lpad, !prof !19
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cont:
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invoke void @callee2(ptr %func)
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to label %ret unwind label %lpad, !prof !20
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lpad:
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%exn = landingpad {ptr, i32}
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cleanup
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unreachable
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ret:
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ret void
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}
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!llvm.module.flags = !{!1}
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!1 = !{i32 1, !"ProfileSummary", !2}
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!2 = !{!3, !4, !5, !6, !7, !8, !9, !10}
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!3 = !{!"ProfileFormat", !"SampleProfile"}
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!4 = !{!"TotalCount", i64 10000}
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!5 = !{!"MaxCount", i64 10}
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!6 = !{!"MaxInternalCount", i64 1}
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!7 = !{!"MaxFunctionCount", i64 2000}
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!8 = !{!"NumCounts", i64 2}
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!9 = !{!"NumFunctions", i64 2}
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!10 = !{!"DetailedSummary", !11}
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!11 = !{!12, !13, !14}
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!12 = !{i32 10000, i64 100, i32 1}
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!13 = !{i32 999000, i64 100, i32 1}
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!14 = !{i32 999999, i64 1, i32 2}
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!15 = !{!"function_entry_count", i64 1000}
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!16 = !{!"branch_weights", i64 1000}
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!17 = !{!"function_entry_count", i32 1500}
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!18 = !{!"VP", i32 0, i64 1500, i64 123, i64 900, i64 456, i64 600}
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!19 = !{!"branch_weights", i32 1500}
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!20 = !{!"branch_weights", i32 1234, i32 5678}
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!21 = !{!"VP", i32 2, i64 1500, i64 789, i64 900, i64 321, i64 600}
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; CHECK-LABEL: define void @caller(
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; CHECK-SAME: ptr [[FUNC:%.*]]) personality ptr @__gxx_personality_v0 !prof [[PROF14:![0-9]+]] {
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; CHECK-NEXT: [[VTABLE_I:%.*]] = load ptr, ptr [[FUNC]], align 8, !prof [[PROF15:![0-9]+]]
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; CHECK-NEXT: [[FUNC_I:%.*]] = load ptr, ptr [[VTABLE_I]], align 8
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; CHECK-NEXT: invoke void [[FUNC_I]]()
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; CHECK-NEXT: to label %[[NEXT_I:.*]] unwind label %[[LPAD_I:.*]], !prof [[PROF16:![0-9]+]]
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; CHECK: [[NEXT_I]]:
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; CHECK-NEXT: invoke void @callee1(ptr [[FUNC_I]])
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; CHECK-NEXT: to label %[[CONT_I:.*]] unwind label %[[LPAD_I]], !prof [[PROF17:![0-9]+]]
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; CHECK: [[CONT_I]]:
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; CHECK-NEXT: invoke void @callee2(ptr [[FUNC_I]])
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; CHECK-NEXT: to label %[[CALLEE_EXIT:.*]] unwind label %[[LPAD_I]], !prof [[PROF18:![0-9]+]]
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;
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; CHECK-LABEL: define void @callee(
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; CHECK-SAME: ptr [[OBJ:%.*]]) personality ptr @__gxx_personality_v0 !prof [[PROF19:![0-9]+]] {
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; CHECK-NEXT: [[VTABLE:%.*]] = load ptr, ptr [[OBJ]], align 8, !prof [[PROF20:![0-9]+]]
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; CHECK-NEXT: [[FUNC:%.*]] = load ptr, ptr [[VTABLE]], align 8
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; CHECK-NEXT: invoke void [[FUNC]]()
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; CHECK-NEXT: to label %[[NEXT:.*]] unwind label %[[LPAD:.*]], !prof [[PROF21:![0-9]+]]
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; CHECK: [[NEXT]]:
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; CHECK-NEXT: invoke void @callee1(ptr [[FUNC]])
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; CHECK-NEXT: to label %[[CONT:.*]] unwind label %[[LPAD]], !prof [[PROF22:![0-9]+]]
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; CHECK: [[CONT]]:
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; CHECK-NEXT: invoke void @callee2(ptr [[FUNC]])
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; CHECK-NEXT: to label %[[RET:.*]] unwind label %[[LPAD]], !prof [[PROF18]]
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; CHECK: [[PROF14]] = !{!"function_entry_count", i64 1000}
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; CHECK: [[PROF15]] = !{!"VP", i32 2, i64 1000, i64 789, i64 600, i64 321, i64 400}
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; CHECK: [[PROF16]] = !{!"VP", i32 0, i64 1000, i64 123, i64 600, i64 456, i64 400}
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; CHECK: [[PROF17]] = !{!"branch_weights", i32 1000}
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; CHECK: [[PROF18]] = !{!"branch_weights", i32 1234, i32 5678}
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; CHECK: [[PROF19]] = !{!"function_entry_count", i64 500}
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; CHECK: [[PROF20]] = !{!"VP", i32 2, i64 500, i64 789, i64 300, i64 321, i64 200}
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; CHECK: [[PROF21]] = !{!"VP", i32 0, i64 500, i64 123, i64 300, i64 456, i64 200}
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; CHECK: [[PROF22]] = !{!"branch_weights", i32 500}
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