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[BOLT] Enable --keep-nops option for Linux kernel by default #86349

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Merged
merged 1 commit into from
Mar 22, 2024
Merged

[BOLT] Enable --keep-nops option for Linux kernel by default #86349

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2 changes: 1 addition & 1 deletion bolt/lib/Rewrite/BinaryPassManager.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -72,7 +72,7 @@ static cl::opt<bool> JTFootprintReductionFlag(
"instructions at jump sites"),
cl::cat(BoltOptCategory));

static cl::opt<bool>
cl::opt<bool>
KeepNops("keep-nops",
cl::desc("keep no-op instructions. By default they are removed."),
cl::Hidden, cl::cat(BoltOptCategory));
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4 changes: 4 additions & 0 deletions bolt/lib/Rewrite/RewriteInstance.cpp
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Expand Up @@ -81,6 +81,7 @@ extern cl::list<std::string> HotTextMoveSections;
extern cl::opt<bool> Hugify;
extern cl::opt<bool> Instrument;
extern cl::opt<JumpTableSupportLevel> JumpTables;
extern cl::opt<bool> KeepNops;
extern cl::list<std::string> ReorderData;
extern cl::opt<bolt::ReorderFunctions::ReorderType> ReorderFunctions;
extern cl::opt<bool> TimeBuild;
Expand Down Expand Up @@ -2031,6 +2032,9 @@ void RewriteInstance::adjustCommandLineOptions() {

if (opts::Lite)
BC->outs() << "BOLT-INFO: enabling lite mode\n";

if (BC->IsLinuxKernel && !opts::KeepNops.getNumOccurrences())
opts::KeepNops = true;
}

namespace {
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15 changes: 7 additions & 8 deletions bolt/test/X86/linux-alt-instruction.s
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Expand Up @@ -6,31 +6,30 @@
# RUN: llvm-mc -filetype=obj -triple x86_64-unknown-unknown %s -o %t.o
# RUN: %clang %cflags -nostdlib %t.o -o %t.exe \
# RUN: -Wl,--image-base=0xffffffff80000000,--no-dynamic-linker,--no-eh-frame-hdr,--no-pie
# RUN: llvm-bolt %t.exe --print-normalized --keep-nops -o %t.out \
# RUN: --alt-inst-feature-size=2 | FileCheck %s
# RUN: llvm-bolt %t.exe --print-normalized --alt-inst-feature-size=2 -o %t.out \
# RUN: | FileCheck %s

## Older kernels used to have padlen field in alt_instr. Check compatibility.

# RUN: llvm-mc -filetype=obj -triple x86_64-unknown-unknown --defsym PADLEN=1 \
# RUN: %s -o %t.o
# RUN: %clang %cflags -nostdlib %t.o -o %t.exe \
# RUN: -Wl,--image-base=0xffffffff80000000,--no-dynamic-linker,--no-eh-frame-hdr,--no-pie
# RUN: llvm-bolt %t.exe --print-normalized --keep-nops --alt-inst-has-padlen \
# RUN: -o %t.out | FileCheck %s
# RUN: llvm-bolt %t.exe --print-normalized --alt-inst-has-padlen -o %t.out \
# RUN: | FileCheck %s

## Check with a larger size of "feature" field in alt_instr.

# RUN: llvm-mc -filetype=obj -triple x86_64-unknown-unknown \
# RUN: --defsym FEATURE_SIZE_4=1 %s -o %t.o
# RUN: %clang %cflags -nostdlib %t.o -o %t.exe \
# RUN: -Wl,--image-base=0xffffffff80000000,--no-dynamic-linker,--no-eh-frame-hdr,--no-pie
# RUN: llvm-bolt %t.exe --print-normalized --keep-nops \
# RUN: --alt-inst-feature-size=4 -o %t.out | FileCheck %s
# RUN: llvm-bolt %t.exe --print-normalized --alt-inst-feature-size=4 -o %t.out \
# RUN: | FileCheck %s

## Check that out-of-bounds read is handled properly.

# RUN: not llvm-bolt %t.exe --print-normalized --keep-nops \
# RUN: --alt-inst-feature-size=2 -o %t.out
# RUN: not llvm-bolt %t.exe --print-normalized --alt-inst-feature-size=2 -o %t.out

# CHECK: BOLT-INFO: Linux kernel binary detected
# CHECK: BOLT-INFO: parsed 2 alternative instruction entries
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4 changes: 2 additions & 2 deletions bolt/test/X86/linux-orc.s
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Expand Up @@ -27,7 +27,7 @@
## Verify ORC bindings to instructions.

# RUN: llvm-bolt %t.exe --print-normalized --dump-orc --print-orc -o %t.out \
# RUN: --bolt-info=0 |& FileCheck %s
# RUN: --keep-nops=0 --bolt-info=0 |& FileCheck %s


## Verify ORC bindings after rewrite.
Expand All @@ -37,7 +37,7 @@

## Verify ORC binding after rewrite when some of the functions are skipped.

# RUN: llvm-bolt %t.exe -o %t.out --skip-funcs=bar --bolt-info=0
# RUN: llvm-bolt %t.exe -o %t.out --skip-funcs=bar --bolt-info=0 --keep-nops=0
# RUN: llvm-bolt %t.out -o %t.out.1 --print-normalized --print-orc \
# RUN: |& FileCheck %s

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2 changes: 1 addition & 1 deletion bolt/test/X86/linux-parainstructions.s
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Expand Up @@ -8,7 +8,7 @@

## Verify paravirtual bindings to instructions.

# RUN: llvm-bolt %t.exe --print-normalized -o %t.out | FileCheck %s
# RUN: llvm-bolt %t.exe --print-normalized -o %t.out --keep-nops=0 | FileCheck %s

# CHECK: BOLT-INFO: Linux kernel binary detected
# CHECK: BOLT-INFO: parsed 2 paravirtual patch sites
Expand Down