54e18b2397
This commit reduces the size of the emitted rebase sections by
generating the REBASE_OPCODE_DO_REBASE_ADD_ADDR_ULEB and
REBASE_OPCODE_DO_REBASE_ULEB_TIMES_SKIPPING_ULEB opcodes.
With this change, chromium_framework's rebase section is a 40% smaller
197 kilobytes, down from the previous 320 kB. That is 6 kB smaller than
what ld64 produces for the same input.
Performance figures from my M1 Mac mini:
x before
+ after
N Min Max Median Avg Stddev
x 10 4.2269349 4.3300061 4.2689675 4.2690016 0.031151669
+ 10 4.219331 4.2914009 4.2398136 4.2448277 0.023817308
No difference proven at 95.0% confidence
Differential Revision: https://reviews.llvm.org/D130180
86 lines
2.7 KiB
ArmAsm
86 lines
2.7 KiB
ArmAsm
# REQUIRES: x86
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# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %s -o %t.o
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# RUN: %lld -dylib %t.o -o %t.dylib
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# RUN: obj2yaml %t.dylib | FileCheck %s
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.text
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.globl _foo
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_foo:
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.data
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# CHECK: RebaseOpcodes:
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# CHECK-NEXT: Opcode: REBASE_OPCODE_SET_TYPE_IMM
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# CHECK-NEXT: Imm: 1
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# CHECK-NEXT: Opcode: REBASE_OPCODE_SET_SEGMENT_AND_OFFSET_ULEB
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# CHECK-NEXT: Imm: 1
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# CHECK-NEXT: ExtraData: [ 0x0 ]
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## 1/ Single rebases with a gap after them are encoded as REBASE_OPCODE_DO_REBASE_ADD_ADDR_ULEB.
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.quad _foo
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.space 16
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# CHECK-NEXT: Opcode: REBASE_OPCODE_DO_REBASE_ADD_ADDR_ULEB
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# CHECK-NEXT: Imm: 0
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# CHECK-NEXT: ExtraData: [ 0x10 ]
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## 2/ Consecutive rebases are encoded as REBASE_OPCODE_DO_REBASE_IMM_TIMES.
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.quad _foo
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.quad _foo
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.quad _foo
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# CHECK-NEXT: Opcode: REBASE_OPCODE_DO_REBASE_IMM_TIMES
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# CHECK-NEXT: Imm: 3
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## 3/ Gaps smaller than 16 words are encoded as REBASE_OPCODE_ADD_ADDR_IMM_SCALED.
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.space 120
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# CHECK-NEXT: Opcode: REBASE_OPCODE_ADD_ADDR_IMM_SCALED
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# CHECK-NEXT: Imm: 15
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## 4/ Rebases with equal gaps betwen them are encoded as REBASE_OPCODE_DO_REBASE_ULEB_TIMES_SKIPPING_ULEB.
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.quad _foo
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.space 16
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.quad _foo
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.space 16
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# CHECK-NEXT: Opcode: REBASE_OPCODE_DO_REBASE_ULEB_TIMES_SKIPPING_ULEB
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# CHECK-NEXT: Imm: 0
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# CHECK-NEXT: ExtraData: [ 0x2, 0x10 ]
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## 5/ Rebase does not become a part of DO_REBASE_ULEB_TIMES_SKIPPING_ULEB if the next rebase is closer than the gap.
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.quad _foo
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.space 8
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# CHECK-NEXT: Opcode: REBASE_OPCODE_DO_REBASE_ADD_ADDR_ULEB
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# CHECK-NEXT: Imm: 0
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# CHECK-NEXT: ExtraData: [ 0x8 ]
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.quad _foo
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.quad _foo
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# CHECK-NEXT: Opcode: REBASE_OPCODE_DO_REBASE_IMM_TIMES
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# CHECK-NEXT: Imm: 2
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## 6/ Large gaps are encoded as REBASE_OPCODE_ADD_ADDR_ULEB.
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.space 128
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# CHECK-NEXT: Opcode: REBASE_OPCODE_ADD_ADDR_ULEB
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# CHECK-NEXT: Imm: 0
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# CHECK-NEXT: ExtraData: [ 0x80 ]
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.quad _foo
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.space 8
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.quad _foo
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.space 8
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.quad _foo
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# CHECK-NEXT: Opcode: REBASE_OPCODE_DO_REBASE_ULEB_TIMES_SKIPPING_ULEB
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# CHECK-NEXT: Imm: 0
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# CHECK-NEXT: ExtraData: [ 0x3, 0x8 ]
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## 7/ An add opcode is emitted if the next relocation is farther away than the DO_REBASE_ULEB_TIMES_SKIPPING_ULEB gap.
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.space 16
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.quad _foo
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# CHECK-NEXT: Opcode: REBASE_OPCODE_ADD_ADDR_IMM_SCALED
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# CHECK-NEXT: Imm: 1
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# CHECK-NEXT: Opcode: REBASE_OPCODE_DO_REBASE_IMM_TIMES
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# CHECK-NEXT: Imm: 1
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## 8/ The rebase section is terminated by REBASE_OPCODE_DONE.
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# CHECK-NEXT: Opcode: REBASE_OPCODE_DONE
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# CHECK-NEXT: Imm: 0
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