From 1b7406b272bae79cf7ce8d39ba8fa408c08720fe Mon Sep 17 00:00:00 2001 From: Wael Yehia Date: Wed, 26 Jul 2023 20:48:13 +0000 Subject: [PATCH] [XCOFF] Do not put MergeableCStrings in their own section The current implementation generates a csect with a ".rodata.str.x.y" prefix for a MergeableCString variable definition. However, a reference to such variable does not get the prefix in its name because there's not enough information in the containing IR. In particular, without seeing the initializer and absent of some other indicators, we cannot tell that the referenced variable is a null- terminated string. When the AIX codegen in llvm was being developed, the prefixing was copied from ELF without having the linker take advantage of the info. Currently, the AIX linker does not have the capability to merge MergeableCString variables. If such feature would ever get implemented, the contract between the linker and compiler would have to be reconsidered. Here's the before and after of this change: ``` @a = global i64 320255973571806, align 8 @strA = unnamed_addr constant [7 x i8] c"hello\0A\00", align 1 ;; Mergeable1ByteCString @strB = unnamed_addr constant [8 x i8] c"Blahah\0A\00", align 1 ;; Mergeable1ByteCString @strC = unnamed_addr constant [2 x i16] [i16 1, i16 0], align 2 ;; Mergeable2ByteCString @strD = unnamed_addr constant [2 x i16] [i16 1, i16 1], align 2 ;; !isMergeableCString @strE = external unnamed_addr constant [2 x i16], align 2 -fdata-sections: .text extern .rodata.str1.1strA .text extern strA 0 SD RO 0 SD RO .text extern .rodata.str1.1strB .text extern strB 0 SD RO 0 SD RO .text extern .rodata.str2.2strC ===> .text extern strC 0 SD RO 0 SD RO .text extern strD .text extern strD 0 SD RO 0 SD RO .data extern a .data extern a 0 SD RW 0 SD RW undef extern strE undef extern strE 0 ER UA 0 ER UA -fno-data-sections: .text unamex .rodata.str1.1 .text unamex .rodata 0 SD RO 0 SD RO .text extern strA .text extern strA 0 LD RO 0 LD RO .text extern strB .text extern strB 0 LD RO 0 LD RO .text unamex .rodata.str2.2 ===> .text extern strC 0 SD RO 0 LD RO .text extern strC .text extern strD 0 LD RO 0 LD RO .text unamex .rodata .data unamex .data 0 SD RO 0 SD RW .text extern strD .data extern a 0 LD RO 0 LD RW .data unamex .data undef extern strE 0 SD RW 0 ER UA .data extern a 0 LD RW undef extern strE 0 ER UA ``` Reviewed by: David Tenty, Fangrui Song Differential Revision: https://reviews.llvm.org/D156202 (cherry picked from commit 9d4e8c09f493280acc7637d904bdc84abc11fdc3) --- llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp | 17 ----------------- llvm/test/CodeGen/PowerPC/aix-return55.ll | 4 ++-- llvm/test/CodeGen/PowerPC/aix-xcoff-data-sections.ll | 10 +++++----- llvm/test/CodeGen/PowerPC/aix-xcoff-mergeable-str.ll | 12 ++++-------- llvm/test/tools/llvm-objdump/XCOFF/symbol-table.test | 4 ++-- 5 files changed, 13 insertions(+), 34 deletions(-) diff --git a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp index 647f570..55fb522 100644 --- a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp +++ b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp @@ -2426,23 +2426,6 @@ MCSection *TargetLoweringObjectFileXCOFF::SelectSectionForGlobal( Name, Kind, XCOFF::CsectProperties(SMC, XCOFF::XTY_CM)); } - if (Kind.isMergeableCString()) { - Align Alignment = GO->getParent()->getDataLayout().getPreferredAlign( - cast(GO)); - - unsigned EntrySize = getEntrySizeForKind(Kind); - std::string SizeSpec = ".rodata.str" + utostr(EntrySize) + "."; - SmallString<128> Name; - Name = SizeSpec + utostr(Alignment.value()); - - if (TM.getDataSections()) - getNameWithPrefix(Name, GO, TM); - - return getContext().getXCOFFSection( - Name, Kind, XCOFF::CsectProperties(XCOFF::XMC_RO, XCOFF::XTY_SD), - /* MultiSymbolsAllowed*/ !TM.getDataSections()); - } - if (Kind.isText()) { if (TM.getFunctionSections()) { return cast(getFunctionEntryPointSymbol(GO, TM)) diff --git a/llvm/test/CodeGen/PowerPC/aix-return55.ll b/llvm/test/CodeGen/PowerPC/aix-return55.ll index 3844803..c7d481c 100644 --- a/llvm/test/CodeGen/PowerPC/aix-return55.ll +++ b/llvm/test/CodeGen/PowerPC/aix-return55.ll @@ -27,8 +27,8 @@ entry: ;CHECKOBJ64: 0000000000000000 <.foo>: ;CHECKOBJ-NEXT: 0: 38 60 00 37 li 3, 55 ;CHECKOBJ-NEXT: 4: 4e 80 00 20 blr{{[[:space:]] *}} -;CHECKOBJ32-NEXT: 00000008 <.rodata.str1.1>: -;CHECKOBJ64-NEXT: 0000000000000008 <.rodata.str1.1>: +;CHECKOBJ32-NEXT: 00000008 <.rodata>: +;CHECKOBJ64-NEXT: 0000000000000008 <.rodata>: ;CHECKOBJ-NEXT: 8: 68 65 6c 6c xori 5, 3, 27756 ;CHECKOBJ-NEXT: c: 6f 77 6f 72 xoris 23, 27, 28530 ;CHECKOBJ-NEXT: 10: 0a 00 00 00 tdlti 0, 0{{[[:space:]] *}} diff --git a/llvm/test/CodeGen/PowerPC/aix-xcoff-data-sections.ll b/llvm/test/CodeGen/PowerPC/aix-xcoff-data-sections.ll index 37445c7..9072e98 100644 --- a/llvm/test/CodeGen/PowerPC/aix-xcoff-data-sections.ll +++ b/llvm/test/CodeGen/PowerPC/aix-xcoff-data-sections.ll @@ -70,16 +70,16 @@ entry: ; CHECK-NEXT: .vbyte 4, 35 # 0x23 ; CHECK-NEXT: .comm a[RW],4,2 ; CHECK-NEXT: .comm f[RW],4,2 -; CHECK-NEXT: .csect .rodata.str1.1L...str[RO],2 +; CHECK-NEXT: .csect L...str[RO],2 ; CHECK-NEXT: .string "abcdefgh" ; CHECK32: .csect p[RW],2 ; CHECK32-NEXT: .globl p[RW] ; CHECK32-NEXT: .align 2 -; CHECK32-NEXT: .vbyte 4, .rodata.str1.1L...str[RO] +; CHECK32-NEXT: .vbyte 4, L...str[RO] ; CHECK64: .csect p[RW],3 ; CHECK64-NEXT: .globl p[RW] ; CHECK64-NEXT: .align 3 -; CHECK64-NEXT: .vbyte 8, .rodata.str1.1L...str[RO] +; CHECK64-NEXT: .vbyte 8, L...str[RO] ; CHECK: .toc ; CHECK-NEXT: L..C0: ; CHECK-NEXT: .tc p[TC],p[RW] @@ -93,7 +93,7 @@ entry: ; CHECKOBJ: 00000038 (idx: 7) const_ivar[RO]: ; CHECKOBJ-NEXT: 38: 00 00 00 23 ; CHECKOBJ-EMPTY: -; CHECKOBJ-NEXT: 0000003c (idx: 9) .rodata.str1.1L...str[RO]: +; CHECKOBJ-NEXT: 0000003c (idx: 9) L...str[RO]: ; CHECKOBJ-NEXT: 3c: 61 62 63 64 ; CHECKOBJ-NEXT: 40: 65 66 67 68 ; CHECKOBJ-NEXT: 44: 00 00 00 00 @@ -156,7 +156,7 @@ entry: ; CHECKSYM: } ; CHECKSYM: } ; CHECKSYM: Symbol { -; CHECKSYM: Name: .rodata.str1.1L...str +; CHECKSYM: Name: L...str ; CHECKSYM: Value (RelocatableAddress): 0x3C ; CHECKSYM: Section: .text ; CHECKSYM: Type: 0x0 diff --git a/llvm/test/CodeGen/PowerPC/aix-xcoff-mergeable-str.ll b/llvm/test/CodeGen/PowerPC/aix-xcoff-mergeable-str.ll index 15402b5..7a5be47 100644 --- a/llvm/test/CodeGen/PowerPC/aix-xcoff-mergeable-str.ll +++ b/llvm/test/CodeGen/PowerPC/aix-xcoff-mergeable-str.ll @@ -26,35 +26,31 @@ entry: ret i8 %1 } -; CHECK: .csect .rodata.str2.2[RO],2 +; CHECK: .csect .rodata[RO],2 ; CHECK-NEXT: .align 1 ; CHECK-NEXT: L..magic16: ; CHECK-NEXT: .vbyte 2, 264 # 0x108 ; CHECK-NEXT: .vbyte 2, 272 # 0x110 ; CHECK-NEXT: .vbyte 2, 213 # 0xd5 ; CHECK-NEXT: .vbyte 2, 0 # 0x0 -; CHECK-NEXT: .csect .rodata.str4.4[RO],2 ; CHECK-NEXT: .align 2 ; CHECK-NEXT: L..magic32: ; CHECK-NEXT: .vbyte 4, 464 # 0x1d0 ; CHECK-NEXT: .vbyte 4, 472 # 0x1d8 ; CHECK-NEXT: .vbyte 4, 413 # 0x19d ; CHECK-NEXT: .vbyte 4, 0 # 0x0 -; CHECK-NEXT: .csect .rodata.str1.1[RO],2 ; CHECK-NEXT: L..strA: ; CHECK-NEXT: .byte 'h,'e,'l,'l,'o,' ,'w,'o,'r,'l,'d,'!,0012,0000 ; CHECK-NEXT: L...str: ; CHECK-NEXT: .string "abcdefgh" -; CHECKOBJ: 00000010 <.rodata.str2.2>: +; CHECKOBJ: 00000010 <.rodata>: ; CHECKOBJ-NEXT: 10: 01 08 01 10 -; CHECKOBJ-NEXT: 14: 00 d5 00 00 {{.*}}{{[[:space:]] *}} -; CHECKOBJ-NEXT: 00000018 <.rodata.str4.4>: +; CHECKOBJ-NEXT: 14: 00 d5 00 00 ; CHECKOBJ-NEXT: 18: 00 00 01 d0 ; CHECKOBJ-NEXT: 1c: 00 00 01 d8 ; CHECKOBJ-NEXT: 20: 00 00 01 9d -; CHECKOBJ-NEXT: 24: 00 00 00 00 {{.*}}{{[[:space:]] *}} -; CHECKOBJ-NEXT: 00000028 <.rodata.str1.1>: +; CHECKOBJ-NEXT: 24: 00 00 00 00 ; CHECKOBJ-NEXT: 28: 68 65 6c 6c ; CHECKOBJ-NEXT: 2c: 6f 20 77 6f ; CHECKOBJ-NEXT: 30: 72 6c 64 21 diff --git a/llvm/test/tools/llvm-objdump/XCOFF/symbol-table.test b/llvm/test/tools/llvm-objdump/XCOFF/symbol-table.test index 815a3a5..f8fc114 100644 --- a/llvm/test/tools/llvm-objdump/XCOFF/symbol-table.test +++ b/llvm/test/tools/llvm-objdump/XCOFF/symbol-table.test @@ -71,7 +71,7 @@ entry: ; SYM-NEXT: 00000000 l .text 00000091 ; SYM-NEXT: 00000000 g F .text (csect: ) 00000000 .bar ; SYM-NEXT: 00000050 g F .text (csect: ) 00000000 .foo -; SYM-NEXT: 00000094 l .text 00000013 .rodata.str1.1L...str +; SYM-NEXT: 00000094 l .text 00000013 L...str ; SYM-NEXT: 000000a8 g O .data 00000004 con ; SYM-NEXT: 000000ac w O .data 00000004 wi ; SYM-NEXT: 000000b0 g O .data 00000004 i @@ -93,7 +93,7 @@ entry: ; SYM-DES-NEXT: 00000000 l .text 00000091 (idx: 3) [PR] ; SYM-DES-NEXT: 00000000 g F .text (csect: (idx: 3) [PR]) 00000000 (idx: 5) .bar ; SYM-DES-NEXT: 00000050 g F .text (csect: (idx: 3) [PR]) 00000000 (idx: 7) .foo -; SYM-DES-NEXT: 00000094 l .text 00000013 (idx: 9) .rodata.str1.1L...str[RO] +; SYM-DES-NEXT: 00000094 l .text 00000013 (idx: 9) L...str[RO] ; SYM-DES-NEXT: 000000a8 g O .data 00000004 (idx: 11) con[RW] ; SYM-DES-NEXT: 000000ac w O .data 00000004 (idx: 13) wi[RW] ; SYM-DES-NEXT: 000000b0 g O .data 00000004 (idx: 15) i[RW] -- 2.7.4