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[BOLT] Don't remove nops in non-simple functions #101964

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[BOLT] Don't remove nops in non-simple functions #101964

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3 changes: 2 additions & 1 deletion bolt/lib/Passes/BinaryPasses.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,7 @@
#include "bolt/Core/ParallelUtilities.h"
#include "bolt/Passes/ReorderAlgorithm.h"
#include "bolt/Passes/ReorderFunctions.h"
#include "bolt/Utils/CommandLineOpts.h"
#include "llvm/Support/CommandLine.h"
#include <atomic>
#include <mutex>
Expand Down Expand Up @@ -1923,7 +1924,7 @@ Error RemoveNops::runOnFunctions(BinaryContext &BC) {
};

ParallelUtilities::PredicateTy SkipFunc = [&](const BinaryFunction &BF) {
return BF.shouldPreserveNops();
return BF.shouldPreserveNops() || (!opts::StrictMode && !BF.isSimple());
};

ParallelUtilities::runOnEachFunction(
Expand Down
38 changes: 38 additions & 0 deletions bolt/test/AArch64/non-simple-nops-preserve.s
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Original file line number Diff line number Diff line change
@@ -0,0 +1,38 @@
# This test checks that the nop instruction is preserved before the
# ADRRelaxation pass. Otherwise the ADRRelaxation pass would
# fail to replace nop+adr to adrp+add for non-simple function.

# RUN: llvm-mc -filetype=obj -triple aarch64-unknown-unknown \
# RUN: %s -o %t.o
# RUN: %clang %cflags %t.o -o %t.exe -Wl,-q
# RUN: llvm-bolt %t.exe -o %t.bolt --adr-relaxation=true \
# RUN: --print-cfg --print-only=_start | FileCheck %s
# RUN: llvm-objdump -d -j .text %t.bolt | \
# RUN: FileCheck --check-prefix=DISASMCHECK %s

# CHECK: Binary Function "_start" after building cfg
# CHECK: IsSimple : 0

# DISASMCHECK: {{.*}}<_start>:
# DISASMCHECK-NEXT: adrp
# DISASMCHECK-NEXT: add
# DISASMCHECK-NEXT: adr

.text
.align 4
.global test
.type test, %function
test:
ret
.size test, .-test

.global _start
.type _start, %function
_start:
nop
adr x0, test
adr x1, 1f
1:
mov x1, x0
br x0
.size _start, .-_start
9 changes: 5 additions & 4 deletions bolt/test/RISCV/reloc-label-diff.s
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Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
// RUN: %clang %cflags -o %t %s
// RUN: llvm-bolt -o %t.bolt %t
// RUN: llvm-bolt --strict -o %t.bolt %t
// RUN: llvm-readelf -x .data %t.bolt | FileCheck %s

.text
Expand All @@ -9,15 +9,16 @@
_start:
// Force BOLT into relocation mode
.reloc 0, R_RISCV_NONE
// BOLT removes this nop so the label difference is initially 8 but should be
// 4 after BOLT processes it.
// BOLT removes this nop so the label difference is initially 12 but should be
// 8 after BOLT processes it.
nop
beq x0, x0, _test_end
addi x1, x1, 1
_test_end:
ret
.size _start, .-_start

.data
// CHECK: Hex dump of section '.data':
// CHECK: 0x{{.*}} 04000000
// CHECK: 0x{{.*}} 08000000
.word _test_end - _start
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