Commit 961f31d8 authored by Fangrui Song's avatar Fangrui Song
Browse files

[TargetMachine] Don't imply dso_local on global variable declarations in Reloc::Static model 

clang/lib/CodeGen/CodeGenModule sets dso_local on applicable global variables,
we don't need to duplicate the work in TargetMachine:shouldAssumeDSOLocal.
(Actually the long-term goal (started by r324535) is to remove as much
additional implied dso_local in TargetMachine:shouldAssumeDSOLocal as possible.)

By not implying dso_local, we will respect dso_local/dso_preemptable specifiers
set by the frontend. This allows the proposed -fno-direct-access-external-data
option to work with -fno-pic and prevent copy relocations.

This patch should be NFC in terms of the Clang behavior because the case we
don't set dso_local is a case Clang sets dso_local. However, some tests don't
set dso_local on some `external global` and expose some differences. Most tests
have been fixed to be more robust in previous commits.
parent fd326398

llvm/lib/Target/TargetMachine.cpp

+12 −3
Original line number Diff line number Diff line
@@ -190,9 +190,18 @@ bool TargetMachine::shouldAssumeDSOLocal(const Module &M, 
    if (Arch == Triple::ppc || TT.isPPC64())

      return false;



    // Check if we can use copy relocations.

    if (!(GV && GV->isThreadLocal()) && RM == Reloc::Static)

    // dso_local is traditionally implied for Reloc::Static. Eventually we shall

    // drop the if block entirely and respect dso_local/dso_preemptable

    // specifiers set by the frontend.

    if (RM == Reloc::Static) {

      // We currently respect dso_local/dso_preemptable specifiers for

      // variables.

      if (!GV || F)

        return true;

      // TODO Remove the special case for x86-32 and wasm.

      if ((Arch == Triple::x86 || TT.isWasm()) && !GV->isThreadLocal())

        return true;

    }

  } else if (TT.isOSBinFormatELF()) {

    // If dso_local allows AsmPrinter::getSymbolPreferLocal to use a local

    // alias, set the flag. We cannot set dso_local for other global values,

llvm/test/CodeGen/AArch64/extern-weak.ll

+4 −6
Original line number Diff line number Diff line
@@ -39,12 +39,10 @@ define i32* @bar() { 


  ret i32* %addr



  ; In the large model, the usual relocations are absolute and can

  ; materialise 0.

; CHECK-LARGE: movz [[ADDR:x[0-9]+]], #:abs_g0_nc:arr_var

; CHECK-LARGE: movk [[ADDR]], #:abs_g1_nc:arr_var

; CHECK-LARGE: movk [[ADDR]], #:abs_g2_nc:arr_var

; CHECK-LARGE: movk [[ADDR]], #:abs_g3:arr_var

  ; Note, In the large model, if dso_local, the relocations are absolute and can materialise 0.

; CHECK-LARGE:      adrp x[[ADDR:[0-9]+]], :got:arr_var

; CHECK-LARGE-NEXT: ldr x[[ADDR]], [x[[ADDR]], :got_lo12:arr_var]

; CHECK-LARGE-NEXT: add x0, x[[ADDR]], #20



; CHECK-TINY: ldr [[BASE:x[0-9]+]], :got:arr_var

; CHECK-TINY: add x0, [[BASE]], #20

llvm/test/CodeGen/AArch64/tiny_model.ll

+13 −12
Original line number Diff line number Diff line
@@ -15,17 +15,17 @@ 
define void @foo1() {

; CHECK-LABEL: foo1:

; CHECK:       // %bb.0: // %entry

; CHECK-NEXT:    adr x8, src

; CHECK-NEXT:    ldr x8, :got:src

; CHECK-NEXT:    ldrb w8, [x8]

; CHECK-NEXT:    adr x9, dst

; CHECK-NEXT:    ldr x9, :got:dst

; CHECK-NEXT:    strb w8, [x9]

; CHECK-NEXT:    ret

;

; CHECK-GLOBISEL-LABEL: foo1:

; CHECK-GLOBISEL:       // %bb.0: // %entry

; CHECK-GLOBISEL-NEXT:    adr x8, src

; CHECK-GLOBISEL-NEXT:    ldr x8, :got:src

; CHECK-GLOBISEL-NEXT:    ldrb w8, [x8]

; CHECK-GLOBISEL-NEXT:    adr x9, dst

; CHECK-GLOBISEL-NEXT:    ldr x9, :got:dst

; CHECK-GLOBISEL-NEXT:    strb w8, [x9]

; CHECK-GLOBISEL-NEXT:    ret

;
@@ -53,15 +53,15 @@ entry: 
define void @foo2() {

; CHECK-LABEL: foo2:

; CHECK:       // %bb.0: // %entry

; CHECK-NEXT:    adr x8, ptr

; CHECK-NEXT:    adr x9, dst

; CHECK-NEXT:    ldr x8, :got:ptr

; CHECK-NEXT:    ldr x9, :got:dst

; CHECK-NEXT:    str x9, [x8]

; CHECK-NEXT:    ret

;

; CHECK-GLOBISEL-LABEL: foo2:

; CHECK-GLOBISEL:       // %bb.0: // %entry

; CHECK-GLOBISEL-NEXT:    adr x8, ptr

; CHECK-GLOBISEL-NEXT:    adr x9, dst

; CHECK-GLOBISEL-NEXT:    ldr x8, :got:ptr

; CHECK-GLOBISEL-NEXT:    ldr x9, :got:dst

; CHECK-GLOBISEL-NEXT:    str x9, [x8]

; CHECK-GLOBISEL-NEXT:    ret

;
@@ -88,16 +88,17 @@ define void @foo3() { 
;

; CHECK-LABEL: foo3:

; CHECK:       // %bb.0: // %entry

; CHECK-NEXT:    adr x8, src

; CHECK-NEXT:    ldr x8, :got:src

; CHECK-NEXT:    ldr x9, :got:ptr

; CHECK-NEXT:    ldrb w8, [x8]

; CHECK-NEXT:    ldr x9, ptr

; CHECK-NEXT:    ldr x9, [x9]

; CHECK-NEXT:    strb w8, [x9]

; CHECK-NEXT:    ret

;

; CHECK-GLOBISEL-LABEL: foo3:

; CHECK-GLOBISEL:       // %bb.0: // %entry

; CHECK-GLOBISEL-NEXT:    adr x8, src

; CHECK-GLOBISEL-NEXT:    adr x9, ptr

; CHECK-GLOBISEL-NEXT:    ldr x8, :got:src

; CHECK-GLOBISEL-NEXT:    ldr x9, :got:ptr

; CHECK-GLOBISEL-NEXT:    ldrb w8, [x8]

; CHECK-GLOBISEL-NEXT:    ldr x9, [x9]

; CHECK-GLOBISEL-NEXT:    strb w8, [x9]

llvm/test/CodeGen/X86/abi-isel.ll

+1066 −981

File changed.

Preview size limit exceeded, changes collapsed.

llvm/test/CodeGen/X86/br-fold.ll

+2 −2
Original line number Diff line number Diff line
@@ -7,7 +7,7 @@ 
; X64_DARWIN: orq

; X64_DARWIN-NEXT: ud2



; X64_LINUX: orq $_ZN11xercesc_2_56XMLUni16fgNotationStringE, %rax

; X64_LINUX: orq _ZN11xercesc_2_56XMLUni16fgNotationStringE@GOTPCREL(%rip), %rax

; X64_LINUX-NEXT: jne

; X64_LINUX-NEXT: %bb8.i329
@@ -18,7 +18,7 @@ 
; X64_WINDOWS_GNU: orq .refptr._ZN11xercesc_2_56XMLUni16fgNotationStringE(%rip), %rax

; X64_WINDOWS_GNU-NEXT: jne



; PS4: orq $_ZN11xercesc_2_56XMLUni16fgNotationStringE, %rax

; PS4: orq _ZN11xercesc_2_56XMLUni16fgNotationStringE@GOTPCREL(%rip), %rax

; PS4-NEXT: ud2



@_ZN11xercesc_2_513SchemaSymbols21fgURI_SCHEMAFORSCHEMAE = external constant [33 x i16], align 32 ; <[33 x i16]*> [#uses=1]