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clang-p2996/llvm/test/CodeGen/X86/code_placement_ext_tsp_large.ll
spupyrev 8d5b694da1 extending code layout alg 
The diff modifies ext-tsp code layout algorithm in the following ways:
(i) fixes merging of cold block chains (this is a port of D129397);
(ii) adjusts the cost model utilized for optimization;
(iii) adjusts some APIs so that the implementation can be used in BOLT; this is
a prerequisite for D129895.

The only non-trivial change is (ii). Here we introduce different weights for
conditional and unconditional branches in the cost model. Based on the new model
it is slightly more important to increase the number of "fall-through
unconditional" jumps, which makes sense, as placing two blocks with an
unconditional jump next to each other reduces the number of jump instructions in
the generated code. Experimentally, this makes a mild impact on the performance;
I've seen up to 0.2%-0.3% perf win on some benchmarks.

Reviewed By: hoy

Differential Revision: https://reviews.llvm.org/D129893
2022-08-24 09:40:25 -07:00

298 lines
9.1 KiB
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; REQUIRES: asserts
; RUN: llc -mcpu=corei7 -mtriple=x86_64-linux -enable-ext-tsp-block-placement=1 -ext-tsp-chain-split-threshold=128 -debug-only=block-placement < %s 2>&1 | FileCheck %s
; RUN: llc -mcpu=corei7 -mtriple=x86_64-linux -enable-ext-tsp-block-placement=1 -ext-tsp-chain-split-threshold=1 -debug-only=block-placement < %s 2>&1 | FileCheck %s -check-prefix=CHECK2
; RUN: llc -mcpu=corei7 -mtriple=x86_64-linux -enable-ext-tsp-block-placement=0 -debug-only=block-placement < %s 2>&1 | FileCheck %s -check-prefix=CHECK3
@yydebug = dso_local global i32 0, align 4
define void @func_large() !prof !0 {
; A largee CFG instance where chain splitting helps to
; compute a better basic block ordering. The test verifies that with chain
; splitting, the resulting layout is improved (e.g., the score is increased).
;
; +----------------+
; | b0 [76 bytes] | -------------------+
; +----------------+ |
; | |
; | 3,065,981,778 |
; v |
; +----------------+ 766,495,444 +----------------+ |
; | b8 [244 bytes] | <--------------- | b2 [4 bytes] | |
; +----------------+ +----------------+ |
; | ^ | |
; | | | 2,299,486,333 |
; | | 766,495,444 v |
; | | +----------------+ |
; | +----------------------- | b3 [12 bytes] | |
; | +----------------+ |
; | | |
; | | 1,532,990,888 |
; | v |
; | +----------------+ | 574,869,946
; | +-------------- | b4 [12 bytes] | |
; | | +----------------+ |
; | | | |
; | | | 574,871,583 |
; | | v |
; | | +----------------+ |
; | | | b5 [116 bytes] | -+ |
; | | +----------------+ | |
; | | | | |
; | | | 1,636 | |
; | | v | |
; | | +----------------+ | |
; | | +------ | b6 [32 bytes] | | |
; | | | +----------------+ | |
; | | | | | |
; | | | | 7 | 3,065,981,778 |
; | | | v | |
; | | | +----------------+ | |
; | | | 1,628 | b9 [16 bytes] | | |
; | | | +----------------+ | |
; | | | | | |
; | | | | 7 | |
; | | | v | |
; | | | +----------------+ | |
; | | +-----> | b7 [12 bytes] | | |
; | | +----------------+ | |
; | | | | |
; | | 958,119,305 | 1,636 | |
; | | v v v
; | | +------------------------------------------+
; | +-------------> | |
; | 1,532,990,889 | b1 [36 bytes] |
; +-------------------------------> | |
; +------------------------------------------+
;
; An expected output with a large chain-split-threshold -- the layout score is
; increased by ~17%
;
; CHECK-LABEL: Applying ext-tsp layout
; CHECK: original layout score: 9171074274.27
; CHECK: optimized layout score: 10844307310.87
; CHECK: b0
; CHECK: b2
; CHECK: b3
; CHECK: b4
; CHECK: b5
; CHECK: b8
; CHECK: b1
; CHECK: b6
; CHECK: b7
; CHECK: b9
;
; An expected output with chain-split-threshold=1 (disabling splitting) -- the
; increase of the layout score is smaller, ~7%:
;
; CHECK2-LABEL: Applying ext-tsp layout
; CHECK2: original layout score: 9171074274.27
; CHECK2: optimized layout score: 9810644873.57
; CHECK2: b0
; CHECK2: b2
; CHECK2: b3
; CHECK2: b4
; CHECK2: b5
; CHECK2: b1
; CHECK2: b8
; CHECK2: b6
; CHECK2: b7
; CHECK2: b9
;
; An expected output with ext-tsp disabled -- the layout is not modified:
;
; CHECK3-LABEL: func_large:
; CHECK3: b0
; CHECK3: b1
; CHECK3: b2
; CHECK3: b3
; CHECK3: b4
; CHECK3: b5
; CHECK3: b6
; CHECK3: b7
; CHECK3: b8
; CHECK3: b9
b0:
%0 = load i32, ptr @yydebug, align 4
%cmp = icmp ne i32 %0, 0
call void @a()
call void @a()
call void @a()
call void @a()
call void @a()
call void @a()
call void @a()
call void @a()
call void @a()
call void @a()
call void @a()
call void @a()
call void @a()
call void @a()
call void @a()
call void @a()
call void @a()
call void @a()
br i1 %cmp, label %b1, label %b2, !prof !1
b1:
call void @b()
call void @b()
call void @b()
call void @b()
call void @b()
call void @b()
call void @b()
call void @b()
ret void
b2:
call void @c()
call void @c()
call void @c()
call void @c()
call void @c()
call void @c()
call void @c()
call void @c()
call void @c()
call void @c()
br i1 %cmp, label %b3, label %b8, !prof !2
b3:
call void @d()
call void @d()
br i1 %cmp, label %b4, label %b8, !prof !3
b4:
call void @e()
call void @e()
br i1 %cmp, label %b5, label %b1, !prof !4
b5:
call void @f()
call void @f()
call void @f()
call void @f()
call void @f()
call void @f()
call void @f()
call void @f()
call void @f()
call void @f()
call void @f()
call void @f()
call void @f()
call void @f()
call void @f()
call void @f()
call void @f()
call void @f()
call void @f()
call void @f()
call void @f()
call void @f()
call void @f()
call void @f()
call void @f()
call void @f()
call void @f()
call void @f()
br i1 %cmp, label %b1, label %b6, !prof !5
b6:
call void @g()
call void @g()
call void @g()
call void @g()
call void @g()
call void @g()
call void @g()
br i1 %cmp, label %b7, label %b9, !prof !6
b7:
call void @h()
call void @h()
br label %b1
b8:
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
call void @i()
br label %b1
b9:
call void @j()
call void @j()
call void @j()
br label %b7
}
declare void @a()
declare void @b()
declare void @c()
declare void @d()
declare void @e()
declare void @f()
declare void @g()
declare void @h()
declare void @i()
declare void @j()
!0 = !{!"function_entry_count", i64 6131963556}
!1 = !{!"branch_weights", i32 3065981778, i32 3065981778}
!2 = !{!"branch_weights", i32 2299486333, i32 766495444}
!3 = !{!"branch_weights", i32 1532990888, i32 766495444}
!4 = !{!"branch_weights", i32 574871583, i32 958119305}
!5 = !{!"branch_weights", i32 574869946, i32 1636}
!6 = !{!"branch_weights", i32 1628, i32 7}
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