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Fix a crash with assembler source and -g. 

llvm-mc or clang with -g normally produces debug info describing the
assembler source itself; however, if that source already contains some
.file/.loc directives, we should instead emit the debug info described
by those directives.  For certain assembler sources seen in the wild
(particularly in the Chrome build) this was causing a crash due to
incorrect assumptions about legal sequences of assembler source text.

Fixes PR38994.

Differential Revision: https://reviews.llvm.org/D63573

llvm-svn: 364039
This commit is contained in:
Paul Robinson 2019-06-21 13:10:19 +00:00
parent 36a999ffb8
commit 26cc5bcb1a
3 changed files with 35 additions and 8 deletions
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15
llvm/include/llvm/MC/MCDwarf.h
View File

@ -261,6 +261,14 @@ public:
HasSource = Source.hasValue();
}
void resetFileTable() {
MCDwarfDirs.clear();
MCDwarfFiles.clear();
RootFile.Name.clear();
resetMD5Usage();
HasSource = false;
}
private:
void emitV2FileDirTables(MCStreamer *MCOS) const;
void emitV5FileDirTables(MCStreamer *MCOS, Optional<MCDwarfLineStr> &LineStr) const;
@ -326,12 +334,7 @@ public:
Header.HasSource = Source.hasValue();
}
void resetRootFile() {
assert(Header.MCDwarfFiles.empty());
Header.RootFile.Name.clear();
Header.resetMD5Usage();
Header.HasSource = false;
}
void resetFileTable() { Header.resetFileTable(); }
bool hasRootFile() const { return !Header.RootFile.Name.empty(); }

4
llvm/lib/MC/MCParser/AsmParser.cpp
View File

@ -3395,9 +3395,9 @@ bool AsmParser::parseDirectiveFile(SMLoc DirectiveLoc) {
} else {
// In case there is a -g option as well as debug info from directive .file,
// we turn off the -g option, directly use the existing debug info instead.
// Also reset any implicit ".file 0" for the assembler source.
// Throw away any implicit file table for the assembler source.
if (Ctx.getGenDwarfForAssembly()) {
Ctx.getMCDwarfLineTable(0).resetRootFile();
Ctx.getMCDwarfLineTable(0).resetFileTable();
Ctx.setGenDwarfForAssembly(false);
}

24
llvm/test/MC/AsmParser/directive_file-g.s Normal file
View File

@ -0,0 +1,24 @@
## Make sure that using -g (or equivalent) on an asm file that already has
## debug-info directives in it will correctly ignore the -g and produce
## debug info corresponding to the directives in the source.
## Note gcc accepts ".file 1" after a label, although not after an opcode.
## If no other directives appear, gcc emits no debug info at all.
# RUN: llvm-mc -g -triple i386-unknown-unknown -filetype=obj %s -o %t
# RUN: llvm-dwarfdump -debug-info -debug-line %t | FileCheck %s
foo:
.file 1 "a.c"
.loc 1 1 1
nop
# CHECK: .debug_info
## gcc does generate a DW_TAG_compile_unit in this case, with or without
## -g on the command line, but we do not.
# CHECK-EMPTY:
# CHECK_NEXT: .debug_line
# CHECK: file_names[ 1]:
# CHECK-NEXT: name: "a.c"
# CHECK-NEXT: dir_index: 0
# CHECK: 0x{{0+}}0 1 1 1 0 0 is_stmt
# CHECK: 0x{{0+}}1 1 1 1 0 0 is_stmt end_sequence