2018-06-01 02:44:12 +08:00
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// REQUIRES: ppc
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// RUN: llvm-mc -filetype=obj -triple=powerpc64le-unknown-linux %s -o %t.o
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[ELF][PPC] Allow PT_LOAD to have overlapping p_offset ranges
This change affects the non-linker script case (precisely, when the
`SECTIONS` command is not used). It deletes 3 alignments at PT_LOAD
boundaries for the default case: the size of a powerpc64 binary can be
decreased by at most 192kb. The technique can be ported to other
targets.
Let me demonstrate the idea with a maxPageSize=65536 example:
When assigning the address to the first output section of a new PT_LOAD,
if the end p_vaddr of the previous PT_LOAD is 0x10020, we advance to
the next multiple of maxPageSize: 0x20000. The new PT_LOAD will thus
have p_vaddr=0x20000. Because p_offset and p_vaddr are congruent modulo
maxPageSize, p_offset will be 0x20000, leaving a p_offset gap [0x10020,
0x20000) in the output.
Alternatively, if we advance to 0x20020, the new PT_LOAD will have
p_vaddr=0x20020. We can pick either 0x10020 or 0x20020 for p_offset!
Obviously 0x10020 is the choice because it leaves no gap. At runtime,
p_vaddr will be rounded down by pagesize (65536 if
pagesize=maxPageSize). This PT_LOAD will load additional initial
contents from p_offset ranges [0x10000,0x10020), which will also be
loaded by the previous PT_LOAD. This is fine if -z noseparate-code is in
effect or if we are not transiting between executable and non-executable
segments.
ld.bfd -z noseparate-code leverages this technique to keep output small.
This patch implements the technique in lld, which is mostly effective on
targets with large defaultMaxPageSize (AArch64/MIPS/PPC: 65536). The 3
removed alignments can save almost 3*65536 bytes.
Two places that rely on p_vaddr%pagesize = 0 have to be updated.
1) We used to round p_memsz(PT_GNU_RELRO) up to commonPageSize (defaults
to 4096 on all targets). Now p_vaddr%commonPageSize may be non-zero.
The updated formula takes account of that factor.
2) Our TP offsets formulae are only correct if p_vaddr%p_align = 0.
Fix them. See the updated comments in InputSection.cpp for details.
On targets that we enable the technique (only PPC64 now),
we can potentially make `p_vaddr(PT_TLS)%p_align(PT_TLS) != 0`
if `sh_addralign(.tdata) < sh_addralign(.tbss)`
This exposes many problems in ld.so implementations, especially the
offsets of dynamic TLS blocks. Known issues:
FreeBSD 13.0-CURRENT rtld-elf (i386/amd64/powerpc/arm64)
glibc (HEAD) i386 and x86_64 https://sourceware.org/bugzilla/show_bug.cgi?id=24606
musl<=1.1.22 on TLS Variant I architectures (aarch64/powerpc64/...)
So, force p_vaddr%p_align = 0 by rounding dot up to p_align(PT_TLS).
The technique will be enabled (with updated tests) for other targets in
subsequent patches.
Reviewed By: ruiu
Differential Revision: https://reviews.llvm.org/D64906
llvm-svn: 369343
2019-08-20 16:34:25 +08:00
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// RUN: ld.lld -shared %t.o -z separate-code -o %t.so
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2018-09-27 03:48:07 +08:00
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// RUN: llvm-readelf -r %t.o | FileCheck --check-prefix=InputRelocs %s
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// RUN: llvm-readelf -r %t.so | FileCheck --check-prefix=OutputRelocs %s
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2018-06-01 02:44:12 +08:00
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// RUN: llvm-objdump --section-headers %t.so | FileCheck --check-prefix=CheckGot %s
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2018-08-29 10:07:58 +08:00
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// RUN: llvm-objdump -d %t.so | FileCheck --check-prefix=Dis %s
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2018-06-01 02:44:12 +08:00
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// RUN: llvm-mc -filetype=obj -triple=powerpc64-unknown-linux %s -o %t.o
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[ELF][PPC] Allow PT_LOAD to have overlapping p_offset ranges
This change affects the non-linker script case (precisely, when the
`SECTIONS` command is not used). It deletes 3 alignments at PT_LOAD
boundaries for the default case: the size of a powerpc64 binary can be
decreased by at most 192kb. The technique can be ported to other
targets.
Let me demonstrate the idea with a maxPageSize=65536 example:
When assigning the address to the first output section of a new PT_LOAD,
if the end p_vaddr of the previous PT_LOAD is 0x10020, we advance to
the next multiple of maxPageSize: 0x20000. The new PT_LOAD will thus
have p_vaddr=0x20000. Because p_offset and p_vaddr are congruent modulo
maxPageSize, p_offset will be 0x20000, leaving a p_offset gap [0x10020,
0x20000) in the output.
Alternatively, if we advance to 0x20020, the new PT_LOAD will have
p_vaddr=0x20020. We can pick either 0x10020 or 0x20020 for p_offset!
Obviously 0x10020 is the choice because it leaves no gap. At runtime,
p_vaddr will be rounded down by pagesize (65536 if
pagesize=maxPageSize). This PT_LOAD will load additional initial
contents from p_offset ranges [0x10000,0x10020), which will also be
loaded by the previous PT_LOAD. This is fine if -z noseparate-code is in
effect or if we are not transiting between executable and non-executable
segments.
ld.bfd -z noseparate-code leverages this technique to keep output small.
This patch implements the technique in lld, which is mostly effective on
targets with large defaultMaxPageSize (AArch64/MIPS/PPC: 65536). The 3
removed alignments can save almost 3*65536 bytes.
Two places that rely on p_vaddr%pagesize = 0 have to be updated.
1) We used to round p_memsz(PT_GNU_RELRO) up to commonPageSize (defaults
to 4096 on all targets). Now p_vaddr%commonPageSize may be non-zero.
The updated formula takes account of that factor.
2) Our TP offsets formulae are only correct if p_vaddr%p_align = 0.
Fix them. See the updated comments in InputSection.cpp for details.
On targets that we enable the technique (only PPC64 now),
we can potentially make `p_vaddr(PT_TLS)%p_align(PT_TLS) != 0`
if `sh_addralign(.tdata) < sh_addralign(.tbss)`
This exposes many problems in ld.so implementations, especially the
offsets of dynamic TLS blocks. Known issues:
FreeBSD 13.0-CURRENT rtld-elf (i386/amd64/powerpc/arm64)
glibc (HEAD) i386 and x86_64 https://sourceware.org/bugzilla/show_bug.cgi?id=24606
musl<=1.1.22 on TLS Variant I architectures (aarch64/powerpc64/...)
So, force p_vaddr%p_align = 0 by rounding dot up to p_align(PT_TLS).
The technique will be enabled (with updated tests) for other targets in
subsequent patches.
Reviewed By: ruiu
Differential Revision: https://reviews.llvm.org/D64906
llvm-svn: 369343
2019-08-20 16:34:25 +08:00
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// RUN: ld.lld -shared %t.o -z separate-code -o %t.so
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2018-09-27 03:48:07 +08:00
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// RUN: llvm-readelf -r %t.o | FileCheck --check-prefix=InputRelocs %s
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// RUN: llvm-readelf -r %t.so | FileCheck --check-prefix=OutputRelocs %s
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2018-06-01 02:44:12 +08:00
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// RUN: llvm-objdump --section-headers %t.so | FileCheck --check-prefix=CheckGot %s
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2018-08-29 10:07:58 +08:00
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// RUN: llvm-objdump -d %t.so | FileCheck --check-prefix=Dis %s
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2018-06-01 02:44:12 +08:00
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.text
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.abiversion 2
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.globl test
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.p2align 4
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.type test,@function
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test:
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.Lfunc_gep0:
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addis 2, 12, .TOC.-.Lfunc_gep0@ha
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addi 2, 2, .TOC.-.Lfunc_gep0@l
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.Lfunc_lep0:
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.localentry test, .Lfunc_lep0-.Lfunc_gep0
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mflr 0
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std 0, 16(1)
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stdu 1, -32(1)
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addis 3, 2, i@got@tlsld@ha
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addi 3, 3, i@got@tlsld@l
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bl __tls_get_addr(i@tlsld)
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nop
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2018-06-12 09:47:02 +08:00
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addis 3, 3, i@dtprel@ha
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lwa 3, i@dtprel@l(3)
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2018-06-01 02:44:12 +08:00
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ld 0, 16(1)
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mtlr 0
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blr
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.globl test_hi
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.p2align 4
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.type test_hi,@function
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test_hi:
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lis 3, j@got@tlsld@h
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blr
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.globl test_16
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.p2align 4
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.type test_16,@function
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test_16:
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li 3, k@got@tlsld
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blr
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.type i,@object
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.section .tdata,"awT",@progbits
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.p2align 2
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i:
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.long 55
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.size i, 4
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.type j,@object
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.section .tbss,"awT",@nobits
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.p2align 2
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j:
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.long 0
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.size j, 4
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.type k,@object
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.section .tdata,"awT",@progbits
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.p2align 3
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k:
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.quad 66
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.size k, 8
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2018-06-12 09:47:02 +08:00
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// Verify that the input contains all the R_PPC64_GOT_TLSLD16* relocations, as
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// well as the DTPREL relocations used in a typical medium code model
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// local-dynamic variable access.
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2018-06-01 02:44:12 +08:00
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// InputRelocs: Relocation section '.rela.text'
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2018-06-12 09:47:02 +08:00
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// InputRelocs: R_PPC64_GOT_TLSLD16_HA {{[0-9a-f]+}} i + 0
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// InputRelocs: R_PPC64_GOT_TLSLD16_LO {{[0-9a-f]+}} i + 0
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// InputRelocs: R_PPC64_TLSLD {{[0-9a-f]+}} i + 0
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// InputRelocs: R_PPC64_DTPREL16_HA {{[0-9a-f]+}} i + 0
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// InputRelocs: R_PPC64_DTPREL16_LO_DS {{[0-9a-f]+}} i + 0
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// InputRelocs: R_PPC64_GOT_TLSLD16_HI {{[0-9a-f]+}} j + 0
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// InputRelocs: R_PPC64_GOT_TLSLD16 {{[0-9a-f]+}} k + 0
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2018-06-01 02:44:12 +08:00
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// The local dynamic version of tls needs to use the same mechanism to look up
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// a variables address as general-dynamic. ie a call to __tls_get_addr with the
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// address of a tls_index struct as the argument. However for local-dynamic
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// variables all will have the same ti_module, and the offset field is left as
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// as 0, so the same struct can be used for every local-dynamic variable
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// used in the shared-object.
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// OutputRelocs: Relocation section '.rela.dyn' at offset 0x{{[0-9a-f]+}} contains 1 entries:
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// OutputRelocs-NEXT: Offset Info Type Symbol's Value Symbol's Name + Addend
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// OutputRelocs-NEXT: R_PPC64_DTPMOD64
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// Check that the got has 3 entries, 1 for the TOC and 1 stucture of 2 entries
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// for the tls variables. Also verify the address so we can check the offsets
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// we calculate for each relocation type.
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// CheckGot: got 00000018 0000000000020100
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// got starts at 0x20100 so .TOC. will be 0x28100, and the tls_index struct is
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// at 0x20108.
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// #ha(i@got@tlsld) --> (0x20108 - 0x28100 + 0x8000) >> 16 = 0
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// #lo(i@got@tlsld) --> (0x20108 - 0x28100) = -7ff8 = -32760
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2018-06-12 09:47:02 +08:00
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// When calculating offset relative to the dynamic thread pointer we have to
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// adjust by 0x8000 since each DTV pointer points 0x8000 bytes past the start of
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// its TLS block.
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// #ha(i@dtprel) --> (0x0 -0x8000 + 0x8000) >> 16 = 0
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// #lo(i@dtprel) --> (0x0 -0x8000) = -0x8000 = -32768
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2018-06-01 02:44:12 +08:00
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// Dis: test:
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// Dis: addis 3, 2, 0
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// Dis-NEXT: addi 3, 3, -32760
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2019-05-10 13:51:00 +08:00
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// Dis-NEXT: bl .+60
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2018-06-12 09:47:02 +08:00
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// Dis-NEXT: ld 2, 24(1)
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// Dis-NEXT: addis 3, 3, 0
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// Dis-NEXT: lwa 3, -32768(3)
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2018-06-01 02:44:12 +08:00
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// #hi(j@got@tlsld) --> (0x20108 - 0x28100 ) > 16 = -1
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// Dis: test_hi:
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// Dis: lis 3, -1
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// k@got@tlsld --> (0x20108 - 0x28100) = -7ff8 = -32760
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// Dis: test_16:
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// Dis: li 3, -32760
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