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Differential D112832

[X86] Don't affect jump tables under +tagged-globals.
ClosedPublic

Authored by morehouse on Oct 29 2021, 9:57 AM.

Details

Reviewers
eugenis
pcc
vitalybuka
Commits
rG33cc0cfd4677: [X86] Don't affect jump tables under +tagged-globals.
Summary

classifyLocalReference(nullptr) is called to get the appropriate
relocation type for jump tables. We should not use @GOTPCREL for this
case.

The new test cases trigger assertions without this patch.

Diff Detail

Event Timeline

morehouse created this revision.Oct 29 2021, 9:57 AM
Herald added subscribers: pengfei, hiraditya. · View Herald TranscriptOct 29 2021, 9:57 AM
morehouse requested review of this revision.Oct 29 2021, 9:57 AM
Herald added a project: Restricted Project. · View Herald TranscriptOct 29 2021, 9:57 AM
Herald added a subscriber: llvm-commits. · View Herald Transcript
morehouse added a project: Restricted Project.Oct 29 2021, 9:57 AM
eugenis accepted this revision.Oct 29 2021, 10:22 AM

LGTM

This revision is now accepted and ready to land.Oct 29 2021, 10:22 AM
This revision was landed with ongoing or failed builds.Oct 29 2021, 10:38 AM
Closed by commit rG33cc0cfd4677: [X86] Don't affect jump tables under +tagged-globals. (authored by morehouse). · Explain Why
This revision was automatically updated to reflect the committed changes.
morehouse added a commit: rG33cc0cfd4677: [X86] Don't affect jump tables under +tagged-globals..
Harbormaster completed remote builds in B131463: Diff 383407.Oct 29 2021, 10:49 AM

Revision Contents

PathSize
llvm/
lib/
Target/
X86/
4 lines
test/
CodeGen/
X86/
23 lines
23 lines

Diff 383426

llvm/lib/Target/X86/X86Subtarget.cpp

Show First 20 Lines • Show All 64 Lines • ▼ Show 20 LinesX86Subtarget::classifyGlobalReference(const GlobalValue *GV) const {
return classifyGlobalReference(GV, *GV->getParent()); return classifyGlobalReference(GV, *GV->getParent());
} }
unsigned char unsigned char
X86Subtarget::classifyLocalReference(const GlobalValue *GV) const { X86Subtarget::classifyLocalReference(const GlobalValue *GV) const {
// Tagged globals have non-zero upper bits, which makes direct references // Tagged globals have non-zero upper bits, which makes direct references
// require a 64-bit immediate. On the small code model this causes relocation // require a 64-bit immediate. On the small code model this causes relocation
// errors, so we go through the GOT instead. // errors, so we go through the GOT instead.
if (AllowTaggedGlobals && TM.getCodeModel() == CodeModel::Small && if (AllowTaggedGlobals && TM.getCodeModel() == CodeModel::Small && GV &&
!isa_and_nonnull<Function>(GV)) !isa<Function>(GV))
return X86II::MO_GOTPCREL; return X86II::MO_GOTPCREL;
// If we're not PIC, it's not very interesting. // If we're not PIC, it's not very interesting.
if (!isPositionIndependent()) if (!isPositionIndependent())
return X86II::MO_NO_FLAG; return X86II::MO_NO_FLAG;
if (is64Bit()) { if (is64Bit()) {
// 64-bit ELF PIC local references may use GOTOFF relocations. // 64-bit ELF PIC local references may use GOTOFF relocations.
▲ Show 20 Lines • Show All 283 Lines • Show Last 20 Lines

llvm/test/CodeGen/X86/tagged-globals-pic.ll

Show All 36 Lines
define void ()* @func_addr() #0 { define void ()* @func_addr() #0 {
; CHECK-LABEL: func_addr: ; CHECK-LABEL: func_addr:
; CHECK: movq func@GOTPCREL(%rip), %rax ; CHECK: movq func@GOTPCREL(%rip), %rax
; CHECK: retq ; CHECK: retq
ret void ()* @func ret void ()* @func
} }
; Jump tables shouldn't go through the GOT.
define i32 @jump_table(i32 %x) #0 {
; CHECK-LABEL: jump_table:
; CHECK-NOT: @GOT
switch i32 %x, label %default [
i32 0, label %1
i32 1, label %2
i32 2, label %3
i32 3, label %4
]
1:
ret i32 7
2:
ret i32 42
3:
ret i32 3
4:
ret i32 8
default:
ret i32 %x
}
attributes #0 = { "target-features"="+tagged-globals" } attributes #0 = { "target-features"="+tagged-globals" }

llvm/test/CodeGen/X86/tagged-globals-static.ll

Show All 36 Lines
define void ()* @func_addr() #0 { define void ()* @func_addr() #0 {
; CHECK-LABEL: func_addr: ; CHECK-LABEL: func_addr:
; CHECK: movl $func, %eax ; CHECK: movl $func, %eax
; CHECK: retq ; CHECK: retq
ret void ()* @func ret void ()* @func
} }
; Jump tables shouldn't go through the GOT.
define i32 @jump_table(i32 %x) #0 {
; CHECK-LABEL: jump_table:
; CHECK-NOT: @GOT
switch i32 %x, label %default [
i32 0, label %1
i32 1, label %2
i32 2, label %3
i32 3, label %4
]
1:
ret i32 7
2:
ret i32 42
3:
ret i32 3
4:
ret i32 8
default:
ret i32 %x
}
attributes #0 = { "target-features"="+tagged-globals" } attributes #0 = { "target-features"="+tagged-globals" }