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clang-p2996/llvm/test/CodeGen/AArch64/min-jump-table.ll
David Sherwood bdc0afc871 [CodeGen][AArch64] Set min jump table entries to 13 for AArch64 targets (#71166) 
There are some workloads that are negatively impacted by using jump
tables when the number of entries is small. The SPEC2017 perlbench
benchmark is one example of this, where increasing the threshold to
around 13 gives a ~1.5% improvement on neoverse-v1. I chose the minimum
threshold based on empirical evidence rather than science, and just
manually increased the threshold until I got the best performance
without impacting other workloads. For neoverse-v1 I saw around ~0.2%
improvement in the SPEC2017 integer geomean, and no overall change for
neoverse-n1. If we find issues with this threshold later on we can
always revisit this.

The most significant SPEC2017 score changes on neoverse-v1 were:

500.perlbench_r: +1.6%
520.omnetpp_r: +0.6%

and the rest saw changes < 0.5%.

I updated CodeGen/AArch64/min-jump-table.ll to reflect the new
threshold. For most of the affected tests I manually set the min number
of entries back to 4 on the RUN line because the tests seem to rely upon
this behaviour.
2023-11-14 13:00:28 +00:00

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; RUN: llc %s -O2 -print-after-isel -mtriple=aarch64-linux-gnu -jump-table-density=40 -aarch64-min-jump-table-entries=0 -o /dev/null 2> %t; FileCheck %s --check-prefixes=CHECK,CHECK0 < %t
; RUN: llc %s -O2 -print-after-isel -mtriple=aarch64-linux-gnu -jump-table-density=40 -aarch64-min-jump-table-entries=2 -o /dev/null 2> %t; FileCheck %s --check-prefixes=CHECK,CHECK2 < %t
; RUN: llc %s -O2 -print-after-isel -mtriple=aarch64-linux-gnu -jump-table-density=40 -aarch64-min-jump-table-entries=4 -o /dev/null 2> %t; FileCheck %s --check-prefixes=CHECK,CHECK4 < %t
; RUN: llc %s -O2 -print-after-isel -mtriple=aarch64-linux-gnu -jump-table-density=40 -aarch64-min-jump-table-entries=8 -o /dev/null 2> %t; FileCheck %s --check-prefixes=CHECK,CHECK8 < %t
; RUN: llc %s -O2 -print-after-isel -mtriple=aarch64-linux-gnu -jump-table-density=40 -aarch64-min-jump-table-entries=12 -o /dev/null 2> %t; FileCheck %s --check-prefixes=CHECK,CHECK12 < %t
; RUN: llc %s -O2 -print-after-isel -mtriple=aarch64-linux-gnu -jump-table-density=40 -o /dev/null 2> %t; FileCheck %s --check-prefixes=CHECK,CHECK-DEFAULT < %t
declare void @ext(i32, i32)
define i32 @jt2(i32 %a, i32 %b) {
entry:
switch i32 %a, label %return [
i32 1, label %bb1
i32 3, label %bb2
]
; CHECK-LABEL: function jt2:
; CHECK0-NEXT: Jump Tables:
; CHECK2-NEXT: Jump Tables:
; CHECK4-NOT: {{^}}Jump Tables:
; CHECK8-NOT: {{^}}Jump Tables:
; CHECK12-NOT: {{^}}Jump Tables:
; CHECK-DEFAULT-NOT: {{^}}Jump Tables:
bb1: tail call void @ext(i32 1, i32 0) br label %return
bb2: tail call void @ext(i32 2, i32 2) br label %return
return: ret i32 %b
}
define i32 @jt4(i32 %a, i32 %b) {
entry:
switch i32 %a, label %return [
i32 1, label %bb1
i32 2, label %bb2
i32 3, label %bb3
i32 5, label %bb4
]
; CHECK-LABEL: function jt4:
; CHECK0-NEXT: Jump Tables:
; CHECK2-NEXT: Jump Tables:
; CHECK4-NEXT: Jump Tables:
; CHECK8-NOT: {{^}}Jump Tables:
; CHECK12-NOT: {{^}}Jump Tables:
; CHECK-DEFAULT-NOT: {{^}}Jump Tables:
bb1: tail call void @ext(i32 1, i32 0) br label %return
bb2: tail call void @ext(i32 3, i32 2) br label %return
bb3: tail call void @ext(i32 4, i32 4) br label %return
bb4: tail call void @ext(i32 5, i32 6) br label %return
return: ret i32 %b
}
define i32 @jt8(i32 %a, i32 %b) {
entry:
switch i32 %a, label %return [
i32 1, label %bb1
i32 2, label %bb2
i32 3, label %bb3
i32 4, label %bb4
i32 5, label %bb5
i32 6, label %bb6
i32 7, label %bb7
i32 9, label %bb8
]
; CHECK-LABEL: function jt8:
; CHECK0-NEXT: Jump Tables:
; CHECK2-NEXT: Jump Tables:
; CHECK4-NEXT: Jump Tables:
; CHECK8-NEXT: Jump Tables:
; CHECK12-NOT: Jump Tables:
; CHECK-DEFAULT-NOT: {{^}}Jump Tables:
bb1: tail call void @ext(i32 1, i32 0) br label %return
bb2: tail call void @ext(i32 2, i32 2) br label %return
bb3: tail call void @ext(i32 3, i32 4) br label %return
bb4: tail call void @ext(i32 4, i32 6) br label %return
bb5: tail call void @ext(i32 5, i32 8) br label %return
bb6: tail call void @ext(i32 6, i32 10) br label %return
bb7: tail call void @ext(i32 7, i32 12) br label %return
bb8: tail call void @ext(i32 8, i32 14) br label %return
return: ret i32 %b
}
define i32 @jt12(i32 %a, i32 %b) {
entry:
switch i32 %a, label %return [
i32 1, label %bb1
i32 2, label %bb2
i32 3, label %bb3
i32 4, label %bb4
i32 5, label %bb5
i32 6, label %bb6
i32 7, label %bb7
i32 8, label %bb8
i32 9, label %bb9
i32 10, label %bb10
i32 11, label %bb11
i32 12, label %bb12
]
; CHECK-LABEL: function jt12:
; CHECK0-NEXT: Jump Tables:
; CHECK2-NEXT: Jump Tables:
; CHECK4-NEXT: Jump Tables:
; CHECK8-NEXT: Jump Tables:
; CHECK12-NEXT: Jump Tables:
; CHECK-DEFAULT-NOT: {{^}}Jump Tables:
bb1: tail call void @ext(i32 1, i32 0) br label %return
bb2: tail call void @ext(i32 2, i32 2) br label %return
bb3: tail call void @ext(i32 3, i32 4) br label %return
bb4: tail call void @ext(i32 4, i32 6) br label %return
bb5: tail call void @ext(i32 5, i32 8) br label %return
bb6: tail call void @ext(i32 6, i32 10) br label %return
bb7: tail call void @ext(i32 7, i32 12) br label %return
bb8: tail call void @ext(i32 8, i32 14) br label %return
bb9: tail call void @ext(i32 9, i32 16) br label %return
bb10: tail call void @ext(i32 10, i32 18) br label %return
bb11: tail call void @ext(i32 11, i32 20) br label %return
bb12: tail call void @ext(i32 12, i32 22) br label %return
return: ret i32 %b
}
define i32 @jt12_min_size(i32 %a, i32 %b) minsize {
entry:
switch i32 %a, label %return [
i32 1, label %bb1
i32 2, label %bb2
i32 3, label %bb3
i32 4, label %bb4
i32 5, label %bb5
i32 6, label %bb6
i32 7, label %bb7
i32 8, label %bb8
i32 9, label %bb9
i32 10, label %bb10
i32 11, label %bb11
i32 12, label %bb12
]
; CHECK-LABEL: function jt12_min_size:
; CHECK0-NEXT: Jump Tables:
; CHECK2-NEXT: Jump Tables:
; CHECK4-NEXT: Jump Tables:
; CHECK8-NEXT: Jump Tables:
; CHECK12-NEXT: Jump Tables:
; CHECK-DEFAULT: Jump Tables:
bb1: tail call void @ext(i32 1, i32 0) br label %return
bb2: tail call void @ext(i32 2, i32 2) br label %return
bb3: tail call void @ext(i32 3, i32 4) br label %return
bb4: tail call void @ext(i32 4, i32 6) br label %return
bb5: tail call void @ext(i32 5, i32 8) br label %return
bb6: tail call void @ext(i32 6, i32 10) br label %return
bb7: tail call void @ext(i32 7, i32 12) br label %return
bb8: tail call void @ext(i32 8, i32 14) br label %return
bb9: tail call void @ext(i32 9, i32 16) br label %return
bb10: tail call void @ext(i32 10, i32 18) br label %return
bb11: tail call void @ext(i32 11, i32 20) br label %return
bb12: tail call void @ext(i32 12, i32 22) br label %return
return: ret i32 %b
}
define i32 @jt13(i32 %a, i32 %b) {
entry:
switch i32 %a, label %return [
i32 1, label %bb1
i32 2, label %bb2
i32 3, label %bb3
i32 4, label %bb4
i32 5, label %bb5
i32 6, label %bb6
i32 7, label %bb7
i32 8, label %bb8
i32 9, label %bb9
i32 10, label %bb10
i32 11, label %bb11
i32 12, label %bb12
i32 13, label %bb13
]
; CHECK-LABEL: function jt13:
; CHECK-NEXT: Jump Tables:
bb1: tail call void @ext(i32 1, i32 0) br label %return
bb2: tail call void @ext(i32 2, i32 2) br label %return
bb3: tail call void @ext(i32 3, i32 4) br label %return
bb4: tail call void @ext(i32 4, i32 6) br label %return
bb5: tail call void @ext(i32 5, i32 8) br label %return
bb6: tail call void @ext(i32 6, i32 10) br label %return
bb7: tail call void @ext(i32 7, i32 12) br label %return
bb8: tail call void @ext(i32 8, i32 14) br label %return
bb9: tail call void @ext(i32 9, i32 16) br label %return
bb10: tail call void @ext(i32 10, i32 18) br label %return
bb11: tail call void @ext(i32 11, i32 20) br label %return
bb12: tail call void @ext(i32 12, i32 22) br label %return
bb13: tail call void @ext(i32 13, i32 24) br label %return
return: ret i32 %b
}
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