bdc0afc871
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.
107 lines
3.1 KiB
LLVM
107 lines
3.1 KiB
LLVM
; RUN: llc -mtriple=aarch64 -aarch64-min-jump-table-entries=4 %s -o - | FileCheck %s
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define void @f0() "patchable-function-entry"="0" "branch-target-enforcement"="true" {
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; CHECK-LABEL: f0:
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; CHECK-NEXT: .Lfunc_begin0:
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; CHECK: // %bb.0:
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; CHECK-NEXT: hint #34
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; CHECK-NEXT: ret
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; CHECK-NOT: .section __patchable_function_entries
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ret void
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}
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;; -fpatchable-function-entry=1 -mbranch-protection=bti
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;; For M=0, place the label .Lpatch0 after the initial BTI.
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define void @f1() "patchable-function-entry"="1" "branch-target-enforcement"="true" {
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; CHECK-LABEL: f1:
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; CHECK-NEXT: .Lfunc_begin1:
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; CHECK-NEXT: .cfi_startproc
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; CHECK-NEXT: // %bb.0:
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; CHECK-NEXT: hint #34
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; CHECK-NEXT: .Lpatch0:
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; CHECK-NEXT: nop
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; CHECK-NEXT: ret
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; CHECK: .section __patchable_function_entries,"awo",@progbits,f1{{$}}
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; CHECK-NEXT: .p2align 3
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; CHECK-NEXT: .xword .Lpatch0
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ret void
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}
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;; -fpatchable-function-entry=2,1 -mbranch-protection=bti
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define void @f2_1() "patchable-function-entry"="1" "patchable-function-prefix"="1" "branch-target-enforcement"="true" {
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; CHECK-LABEL: .type f2_1,@function
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; CHECK-NEXT: .Ltmp0:
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; CHECK-NEXT: nop
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; CHECK-NEXT: f2_1:
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; CHECK-NEXT: .Lfunc_begin2:
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; CHECK-NEXT: .cfi_startproc
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; CHECK-NEXT: // %bb.0:
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; CHECK-NEXT: hint #34
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; CHECK-NEXT: nop
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; CHECK-NEXT: ret
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; CHECK: .Lfunc_end2:
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; CHECK-NEXT: .size f2_1, .Lfunc_end2-f2_1
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; CHECK: .section __patchable_function_entries,"awo",@progbits,f2_1{{$}}
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; CHECK-NEXT: .p2align 3
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; CHECK-NEXT: .xword .Ltmp0
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ret void
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}
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;; -fpatchable-function-entry=1 -mbranch-protection=bti
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;; We add BTI c even when the function has internal linkage
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define internal void @f1i(i64 %v) "patchable-function-entry"="1" "branch-target-enforcement"="true" {
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; CHECK-LABEL: f1i:
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; CHECK-NEXT: .Lfunc_begin3:
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; CHECK: // %bb.0:
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; CHECK-NEXT: hint #34
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; CHECK-NEXT: .Lpatch1:
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; CHECK-NEXT: nop
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;; Other basic blocks have BTI, but they don't affect our decision to not create .Lpatch0
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; CHECK: .LBB{{.+}} // %sw.bb1
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; CHECK-NEXT: hint #36
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; CHECK: .section __patchable_function_entries,"awo",@progbits,f1i{{$}}
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; CHECK-NEXT: .p2align 3
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; CHECK-NEXT: .xword .Lpatch1
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entry:
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switch i64 %v, label %sw.bb0 [
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i64 1, label %sw.bb1
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i64 2, label %sw.bb2
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i64 3, label %sw.bb3
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i64 4, label %sw.bb4
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]
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sw.bb0:
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call void asm sideeffect "nop", ""()
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ret void
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sw.bb1:
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call void asm sideeffect "", ""()
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ret void
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sw.bb2:
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call void asm sideeffect "", ""()
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ret void
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sw.bb3:
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call void asm sideeffect "", ""()
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ret void
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sw.bb4:
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call void asm sideeffect "", ""()
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ret void
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}
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;; Test the interaction with -fsanitize=function.
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; CHECK: .type sanitize_function,@function
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; CHECK-NEXT: .Ltmp{{.*}}:
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; CHECK-NEXT: nop
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; CHECK-NEXT: .word 3238382334 // 0xc105cafe
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; CHECK-NEXT: .word 42
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; CHECK-NEXT: sanitize_function:
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; CHECK-NEXT: .Lfunc_begin{{.*}}:
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; CHECK-NEXT: .cfi_startproc
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; CHECK-NEXT: // %bb.0:
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; CHECK-NEXT: hint #34
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; CHECK-NEXT: nop
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; CHECK-NEXT: ret
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define void @sanitize_function(ptr noundef %x) "patchable-function-prefix"="1" "patchable-function-entry"="1" "branch-target-enforcement"="true" !func_sanitize !0 {
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ret void
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}
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!0 = !{i32 3238382334, i32 42}
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