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Reapply: StackProtector: ignore debug insts when splitting blocks. 

When deciding where to split a block to insert stack guard checks, we should
move past any debug instructions we see that might (e.g.) be separating a tail
call from its frame wrangling.

This time, also don't run off the front of a basic block.
This commit is contained in:
Tim Northover 2022-02-10 13:28:50 +00:00 committed by Tim Northover
parent 7f41643ef0
commit a87d3ba61c
3 changed files with 79 additions and 2 deletions
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6
llvm/lib/CodeGen/CodeGenCommonISel.cpp
View File

@ -129,7 +129,9 @@ llvm::findSplitPointForStackProtector(MachineBasicBlock *BB,
MachineBasicBlock::iterator Start = BB->begin();
MachineBasicBlock::iterator Previous = SplitPoint;
--Previous;
do {
--Previous;
} while (Previous != Start && Previous->isDebugInstr());
if (TII.isTailCall(*SplitPoint) &&
Previous->getOpcode() == TII.getCallFrameDestroyOpcode()) {
@ -142,7 +144,7 @@ llvm::findSplitPointForStackProtector(MachineBasicBlock *BB,
// ADJCALLSTACKUP ...
// TAILJMP somewhere
// On the other hand, it could be an unrelated call in which case this tail
// call has to register moves of its own and should be the split point. For
// call has no register moves of its own and should be the split point. For
// example:
// ADJCALLSTACKDOWN
// CALL something_else

40
llvm/test/CodeGen/AArch64/tailcall-ssp-split-debug.ll Normal file
View File

@ -0,0 +1,40 @@
; RUN: llc -mtriple=arm64-apple-ios %s -o - | FileCheck %s
define swifttailcc void @foo(i8* %call) ssp {
; CHECK-LABEL: foo:
%var = alloca [28 x i8], align 16
br i1 undef, label %if.then, label %if.end
if.then:
ret void
if.end:
; CHECK: mov x[[NULL:[0-9]+]], xzr
; CHECK: ldr [[FPTR:x[0-9]+]], [x[[NULL]]]
; CHECK: br [[FPTR]]
call void @llvm.dbg.value(metadata i8* %call, metadata !19, metadata !DIExpression()), !dbg !21
%fptr = load void (i8*)*, void (i8*)** null, align 8
musttail call swifttailcc void %fptr(i8* null)
ret void
}
declare i8* @pthread_getspecific()
; Function Attrs: nofree nosync nounwind readnone speculatable willreturn
declare void @llvm.dbg.value(metadata, metadata, metadata) #1
!llvm.module.flags = !{!2}
!llvm.dbg.cu = !{!11}
!2 = !{i32 2, !"Debug Info Version", i32 3}
!11 = distinct !DICompileUnit(language: DW_LANG_C99, file: !12, producer: "Apple clang version 13.1.6 (clang-1316.0.17.4)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !13, splitDebugInlining: false, nameTableKind: None, sysroot: "/Library/Developer/CommandLineTools/SDKs/MacOSX12.3.sdk", sdk: "MacOSX12.3.sdk")
!12 = !DIFile(filename: "tmp.c", directory: "/Users/tim/llvm-internal/llvm-project/build")
!13 = !{}
!14 = !{!"Apple clang version 13.1.6 (clang-1316.0.17.4)"}
!15 = distinct !DISubprogram(name: "bar", scope: !12, file: !12, line: 3, type: !16, scopeLine: 3, flags: DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !11, retainedNodes: !18)
!16 = !DISubroutineType(types: !17)
!17 = !{null}
!18 = !{!19}
!19 = !DILocalVariable(name: "var", scope: !15, file: !12, line: 4, type: !20)
!20 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
!21 = !DILocation(line: 0, scope: !15)

35
llvm/test/CodeGen/X86/tailcall-ssp-split-debug.ll Normal file
View File

@ -0,0 +1,35 @@
; RUN: llc -mtriple=x86_64-apple-macosx %s -o - | FileCheck %s
define void @foo() ssp {
; CHECK-LABEL: foo:
%ptr = alloca [32 x i32], align 16
br i1 undef, label %true, label %false
true:
unreachable
false:
call void @llvm.dbg.value(metadata i8** undef, metadata !19, metadata !DIExpression()) #2, !dbg !21
ret void
}
declare i8* @pthread_getspecific()
; Function Attrs: nofree nosync nounwind readnone speculatable willreturn
declare void @llvm.dbg.value(metadata, metadata, metadata) #1
!llvm.module.flags = !{!2}
!llvm.dbg.cu = !{!11}
!2 = !{i32 2, !"Debug Info Version", i32 3}
!11 = distinct !DICompileUnit(language: DW_LANG_C99, file: !12, producer: "Apple clang version 13.1.6 (clang-1316.0.17.4)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !13, splitDebugInlining: false, nameTableKind: None, sysroot: "/Library/Developer/CommandLineTools/SDKs/MacOSX12.3.sdk", sdk: "MacOSX12.3.sdk")
!12 = !DIFile(filename: "tmp.c", directory: "/Users/tim/llvm-internal/llvm-project/build")
!13 = !{}
!14 = !{!"Apple clang version 13.1.6 (clang-1316.0.17.4)"}
!15 = distinct !DISubprogram(name: "bar", scope: !12, file: !12, line: 3, type: !16, scopeLine: 3, flags: DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !11, retainedNodes: !18)
!16 = !DISubroutineType(types: !17)
!17 = !{null}
!18 = !{!19}
!19 = !DILocalVariable(name: "var", scope: !15, file: !12, line: 4, type: !20)
!20 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
!21 = !DILocation(line: 0, scope: !15)