From 87c0f6773970f41f0e464690862f05bc109ee8d0 Mon Sep 17 00:00:00 2001 From: Nathan Lanza Date: Sat, 8 Apr 2023 02:10:27 -0400 Subject: [PATCH] [Outliner] Add an option to only enable outlining of patterns above a certain threshold Outlining isn't always a win when the saved instruction count is >= 1. The overhead of representing a new function in the binary depends on exception metadata and alignment. So parameterize this for local tuning. Reviewed By: paquette Differential Revision: https://reviews.llvm.org/D136774 --- llvm/lib/CodeGen/MachineOutliner.cpp | 9 +- .../AArch64/machine-outliner-threshold.mir | 114 ++++++++++++++++++ 2 files changed, 121 insertions(+), 2 deletions(-) create mode 100644 llvm/test/CodeGen/AArch64/machine-outliner-threshold.mir diff --git a/llvm/lib/CodeGen/MachineOutliner.cpp b/llvm/lib/CodeGen/MachineOutliner.cpp index 8d72208e8c581..d116c5445e307 100644 --- a/llvm/lib/CodeGen/MachineOutliner.cpp +++ b/llvm/lib/CodeGen/MachineOutliner.cpp @@ -116,6 +116,11 @@ static cl::opt OutlinerReruns( cl::desc( "Number of times to rerun the outliner after the initial outline")); +static cl::opt OutlinerBenefitThreshold( + "outliner-benefit-threshold", cl::init(1), cl::Hidden, + cl::desc( + "The minimum size in bytes before an outlining candidate is accepted")); + namespace { /// Maps \p MachineInstrs to unsigned integers and stores the mappings. @@ -664,7 +669,7 @@ void MachineOutliner::findCandidates( continue; // Is it better to outline this candidate than not? - if (OF->getBenefit() < 1) { + if (OF->getBenefit() < OutlinerBenefitThreshold) { emitNotOutliningCheaperRemark(StringLen, CandidatesForRepeatedSeq, *OF); continue; } @@ -840,7 +845,7 @@ bool MachineOutliner::outline(Module &M, }); // If we made it unbeneficial to outline this function, skip it. - if (OF.getBenefit() < 1) + if (OF.getBenefit() < OutlinerBenefitThreshold) continue; // It's beneficial. Create the function and outline its sequence's diff --git a/llvm/test/CodeGen/AArch64/machine-outliner-threshold.mir b/llvm/test/CodeGen/AArch64/machine-outliner-threshold.mir new file mode 100644 index 0000000000000..b3efb29abf5b4 --- /dev/null +++ b/llvm/test/CodeGen/AArch64/machine-outliner-threshold.mir @@ -0,0 +1,114 @@ +# RUN: llc -mtriple=aarch64--- -run-pass=machine-outliner -verify-machineinstrs %s -o - | FileCheck %s +# RUN: llc -mtriple=aarch64--- -outliner-benefit-threshold=10 -run-pass=machine-outliner -verify-machineinstrs %s -o - | FileCheck %s -check-prefix=THRESHOLD +--- | + + define void @baz() #0 { + ret void + } + + define void @bar(i32 %a) #0 { + ret void + } + + attributes #0 = { noredzone } +... +--- +# Check that two we outline two different sequences, one from bb1 and one from +# bb2 when the threshold is 1. +# CHECK-LABEL: bb.1: +# CHECK: BL @OUTLINED_FUNCTION_[[F0:[0-9]+]], implicit-def $lr, implicit $sp +# CHECK-NEXT: $w11 = ORRWri $wzr, 1 +# CHECK-NEXT: $w11 = ORRWri $wzr, 1 +# CHECK-NEXT: $w11 = ORRWri $wzr, 2 +# CHECK-NEXT: BL @baz, implicit-def dead $lr, implicit $sp +# CHECK-NEXT: BL @OUTLINED_FUNCTION_[[F0]], implicit-def $lr, implicit $sp +# CHECK-NEXT: $w11 = ORRWri $wzr, 1 +# CHECK-NEXT: $w11 = ORRWri $wzr, 1 +# CHECK-NEXT: $w8 = ORRWri $wzr, 0 +# CHECK-NOT: $w11 = KILL renamable $w11, implicit killed $w11 + +# CHECK-LABEL: bb.2: +# CHECK: BL @OUTLINED_FUNCTION_[[F1:[0-9]+]], implicit-def $lr, implicit $sp +# CHECK-NEXT: $w9 = ORRWri $wzr, 0 +# CHECK-NEXT: BL @OUTLINED_FUNCTION_[[F1]], implicit-def $lr, implicit $sp +# CHECK-NEXT: $w8 = ORRWri $wzr, 0 +# CHECK-NOT: $w11 = KILL renamable $w11, implicit killed $w11 + +# Check that the sequences in bb.2 don't get outlined with a threshold of 10 but +# the sequences in bb.1 do. +# THRESHOLD-LABEL: bb.1: +# THRESHOLD: BL @OUTLINED_FUNCTION_[[F0:[0-9]+]], implicit-def $lr, implicit $sp +# THRESHOLD-NEXT: $w11 = ORRWri $wzr, 1 +# THRESHOLD-NEXT: $w11 = ORRWri $wzr, 1 +# THRESHOLD-NEXT: $w11 = ORRWri $wzr, 2 +# THRESHOLD-NEXT: BL @baz, implicit-def dead $lr, implicit $sp +# THRESHOLD-NEXT: BL @OUTLINED_FUNCTION_[[F0]], implicit-def $lr, implicit $sp +# THRESHOLD-NEXT: $w11 = ORRWri $wzr, 1 +# THRESHOLD-NEXT: $w11 = ORRWri $wzr, 1 +# THRESHOLD-NEXT: $w8 = ORRWri $wzr, 0 +# THRESHOLD-NOT: $w11 = KILL renamable $w11, implicit killed $w11 + +# THRESHOLD-LABEL: bb.2: +# THRESHOLD-NOT: BL @OUTLINED_FUNCTION +name: bar +tracksRegLiveness: true +body: | + bb.0: + liveins: $w0, $lr, $w8 + $sp = frame-setup SUBXri $sp, 32, 0 + $fp = frame-setup ADDXri $sp, 16, 0 + + bb.1: + BL @baz, implicit-def dead $lr, implicit $sp + $w11 = ORRWri $wzr, 1 + $w11 = ORRWri $wzr, 1 + $w11 = KILL renamable $w11, implicit killed $w11 + $w11 = ORRWri $wzr, 1 + $w11 = ORRWri $wzr, 1 + BL @baz, implicit-def dead $lr, implicit $sp + $w11 = ORRWri $wzr, 1 + $w11 = ORRWri $wzr, 1 + $w11 = ORRWri $wzr, 2 + BL @baz, implicit-def dead $lr, implicit $sp + $w11 = ORRWri $wzr, 1 + $w11 = ORRWri $wzr, 1 + $w11 = ORRWri $wzr, 1 + $w11 = ORRWri $wzr, 1 + BL @baz, implicit-def dead $lr, implicit $sp + $w11 = ORRWri $wzr, 1 + $w11 = ORRWri $wzr, 1 + $w8 = ORRWri $wzr, 0 + + bb.2: + $w15 = ORRWri $wzr, 1 + $w15 = ORRWri $wzr, 1 + $w15 = ORRWri $wzr, 1 + $w15 = ORRWri $wzr, 1 + $x15 = ADDXri $sp, 48, 0; + $w9 = ORRWri $wzr, 0 + $w15 = ORRWri $wzr, 1 + $w15 = ORRWri $wzr, 1 + $w15 = ORRWri $wzr, 1 + $w15 = ORRWri $wzr, 1 + $x15 = ADDXri $sp, 48, 0; + $w8 = ORRWri $wzr, 0 + + bb.3: + $fp, $lr = LDPXi $sp, 2 + $sp = ADDXri $sp, 32, 0 + RET undef $lr + +... +--- +name: baz +tracksRegLiveness: true +body: | + bb.0: + liveins: $w0, $lr, $w8 + RET undef $lr + +# CHECK-LABEL: name: OUTLINED_FUNCTION_{{[0-9]}} +# CHECK-LABEL: name: OUTLINED_FUNCTION_{{[1-9]}} + +# THRESHOLD-LABEL: name: OUTLINED_FUNCTION_{{[0-9]}} +# THRESHOLD-NOT: name: OUTLINED_FUNCTION_{{[1-9]}}