[llvm-dev] Using braces in InstAlias asm string
Cullen Rhodes via llvm-dev
llvm-dev at lists.llvm.org
Wed Apr 15 09:43:27 PDT 2020
Hi,
I'm adding MC support for a set of instructions containing braces and I'm
hitting an issue with InstAlias. I've reproduced it with the ldraa instruction -
the first AArch64 instruction I found in AArch64InstrFormats.td that uses
InstAlias.
The instruction takes a dst register, base address and optional offset. An
alias is used to implement no offset form:
multiclass AuthLoad<bit M, string asm, Operand opr> {
def indexed : BaseAuthLoad<M, 0, (outs GPR64:$Rt),
(ins GPR64sp:$Rn, opr:$offset),
asm, "\t$Rt, [$Rn, $offset]", "", opr>;
def writeback : BaseAuthLoad<M, 1, (outs GPR64sp:$wback, GPR64:$Rt),
(ins GPR64sp:$Rn, opr:$offset),
asm, "\t$Rt, [$Rn, $offset]!",
"$Rn = $wback, at earlyclobber $wback", opr>;
def : InstAlias<asm # "\t$Rt, [$Rn]",
(!cast<Instruction>(NAME # "indexed") GPR64:$Rt, GPR64sp:$Rn, 0)>; <-- HERE
def : InstAlias<asm # "\t$Rt, [$wback]!",
(!cast<Instruction>(NAME # "writeback") GPR64sp:$wback, GPR64:$Rt, 0), 0>;
}
Example usage:
$ echo "[0x20,0x04,0x20,0xf8]" | ./bin/llvm-mc -triple=aarch64 -show-encoding -mattr=+v8.3a -disassemble
.text
ldraa x0, [x1] // encoding: [0x20,0x04,0x20,0xf8]
To recreate the issue I tried adding braces around the dst reg and base
address, e.g.
ldraa {x0, [x1]}
The first thing I tried was double braces "{{}}" which seems to work for the asm
string in an instruction definition, e.g.
diff --git a/llvm/lib/Target/AArch64/AArch64InstrFormats.td b/llvm/lib/Target/AArch64/AArch64InstrFormats.td
index 6b23c7c..62bf67d 100644
--- a/llvm/lib/Target/AArch64/AArch64InstrFormats.td
+++ b/llvm/lib/Target/AArch64/AArch64InstrFormats.td
@@ -1632,7 +1632,7 @@ class BaseAuthLoad<bit M, bit W, dag oops, dag iops, string asm,
multiclass AuthLoad<bit M, string asm, Operand opr> {
def indexed : BaseAuthLoad<M, 0, (outs GPR64:$Rt),
(ins GPR64sp:$Rn, opr:$offset),
- asm, "\t$Rt, [$Rn, $offset]", "", opr>;
+ asm, "\t{{$Rt, [$Rn, $offset]}}", "", opr>;
def writeback : BaseAuthLoad<M, 1, (outs GPR64sp:$wback, GPR64:$Rt),
(ins GPR64sp:$Rn, opr:$offset),
asm, "\t$Rt, [$Rn, $offset]!",
but doesn't work when defining an InstAlias, e.g.
diff --git a/llvm/lib/Target/AArch64/AArch64InstrFormats.td b/llvm/lib/Target/AArch64/AArch64InstrFormats.td
index 6b23c7c..44fb9a3 100644
--- a/llvm/lib/Target/AArch64/AArch64InstrFormats.td
+++ b/llvm/lib/Target/AArch64/AArch64InstrFormats.td
@@ -1638,7 +1638,7 @@ multiclass AuthLoad<bit M, string asm, Operand opr> {
asm, "\t$Rt, [$Rn, $offset]!",
"$Rn = $wback, at earlyclobber $wback", opr>;
- def : InstAlias<asm # "\t$Rt, [$Rn]",
+ def : InstAlias<asm # "\t{{$Rt, [$Rn]}}",
(!cast<Instruction>(NAME # "indexed") GPR64:$Rt, GPR64sp:$Rn, 0)>;
where I'm see the following error from TableGen:
[17/124] Building AArch64GenAsmMatcher.inc...
FAILED: cd ./llvm-project/build && ./llvm-project/build/bin/llvm-tblgen -gen-asm-matcher -I ./llvm-project/llvm/lib/Target/AArch64 -I /usr/include/libxml2 -I ./llvm-project/build/include -I ./llvm-project/llvm/include -I ./llvm-project/llvm/lib/Target ./llvm-project/llvm/lib/Target/AArch64/AArch64.td --write-if-changed -o lib/Target/AArch64/AArch64GenAsmMatcher.inc -d lib/Target/AArch64/AArch64GenAsmMatcher.inc.d
Included from ./llvm-project/llvm/lib/Target/AArch64/AArch64.td:431:
Included from ./llvm-project/llvm/lib/Target/AArch64/AArch64InstrInfo.td:588:
./llvm-project/llvm/lib/Target/AArch64/AArch64InstrFormats.td:1641:3: error: Instruction 'anonymous_2396' has operand 'Rt' that doesn't appear in asm string!
def : InstAlias<asm # "\t{{$Rt, [$Rn]}}",
^
Included from ./llvm-project/llvm/lib/Target/AArch64/AArch64.td:431:
./llvm-project/llvm/lib/Target/AArch64/AArch64InstrInfo.td:932:17: note: instantiated from multiclass
defm LDRAA : AuthLoad<0, "ldraa", simm10Scaled>;
^
[17/71] Building AArch64GenDAGISel.inc...
ninja: build stopped: subcommand failed.
which led me to think it's trying to do some form of substitution for braces, so
I tried the following hack using an OR where both sides are the same in the asm
string:
diff --git a/llvm/lib/Target/AArch64/AArch64InstrFormats.td b/llvm/lib/Target/AArch64/AArch64InstrFormats.td
index 6b23c7c..97ed49e 100644
--- a/llvm/lib/Target/AArch64/AArch64InstrFormats.td
+++ b/llvm/lib/Target/AArch64/AArch64InstrFormats.td
@@ -1638,7 +1638,7 @@ multiclass AuthLoad<bit M, string asm, Operand opr> {
asm, "\t$Rt, [$Rn, $offset]!",
"$Rn = $wback, at earlyclobber $wback", opr>;
- def : InstAlias<asm # "\t$Rt, [$Rn]",
+ def : InstAlias<asm # "\t{{$Rt, [$Rn]}|{$Rt, [$Rn]}}",
(!cast<Instruction>(NAME # "indexed") GPR64:$Rt, GPR64sp:$Rn, 0)>;
def : InstAlias<asm # "\t$Rt, [$wback]!",
Which seems to work fine.
Example usage:
$ echo "[0x20,0x04,0x20,0xf8]" | ./bin/llvm-mc -triple=aarch64 -show-encoding -mattr=+v8.3a -disassemble
.text
ldraa {x0, [x1]} // encoding: [0x20,0x04,0x20,0xf8]
FWIW I also tried double escaping, e.g.
diff --git a/llvm/lib/Target/AArch64/AArch64InstrFormats.td b/llvm/lib/Target/AArch64/AArch64InstrFormats.td
index 6b23c7c..1d74aaf 100644
--- a/llvm/lib/Target/AArch64/AArch64InstrFormats.td
+++ b/llvm/lib/Target/AArch64/AArch64InstrFormats.td
@@ -1638,7 +1638,7 @@ multiclass AuthLoad<bit M, string asm, Operand opr> {
asm, "\t$Rt, [$Rn, $offset]!",
"$Rn = $wback, at earlyclobber $wback", opr>;
- def : InstAlias<asm # "\t$Rt, [$Rn]",
+ def : InstAlias<asm # "\t\\{$Rt, [$Rn]\\}",
(!cast<Instruction>(NAME # "indexed") GPR64:$Rt, GPR64sp:$Rn, 0)>;
Which actually worked on LLVM 9 but warnings are emitted:
[20/70] Building CXX object lib/Target/AArch64/MCTargetDesc/CMakeFiles/LLVMAArch64Desc.dir/AArch64InstPrinter.cpp.o
In file included from ./llvm-project/llvm/lib/Target/AArch64/MCTargetDesc/AArch64InstPrinter.cpp:39:
lib/Target/AArch64/AArch64GenAsmWriter.inc:23094:23: warning: use of non-standard escape character '\{' [-Wpedantic]
/* 7811 */ "ldraa \{$\x01, [$\x02]\}\0"
^~
On upstream master I also hit a bunch of the following asserts, just to clarify
addv is unrelated and I made no changes there. This is just an example from one
of the many failures:
********************
FAIL: LLVM :: CodeGen/AArch64/aarch64-addv.ll (6528 of 36856)
******************** TEST 'LLVM :: CodeGen/AArch64/aarch64-addv.ll' FAILED ********************
Script:
--
: 'RUN: at line 1'; ./llvm-project/build/bin/llc < ./llvm-project/llvm/test/CodeGen/AArch64/aarch64-addv.ll -mtriple=aarch64-eabi -aarch64-neon-syntax=generic | ./llvm-project/build/bin/FileCheck ./llvm-project/llvm/test/CodeGen/AArch64/aarch64-addv.ll
--
Exit Code: 2
Command Output (stderr):
--
llc: ./llvm-project/llvm/lib/MC/MCInstPrinter.cpp:168: const char *llvm::MCInstPrinter::matchAliasPatterns(const llvm::MCInst *, const llvm::MCSubtargetInfo *, const llvm::AliasMatchingData &): Assertion `AsmStrOffset < M.AsmStrings.size() && (AsmStrOffset == 0 || M.AsmStrings[AsmStrOffset - 1] == '\0') && "bad asm string offset"' failed.
PLEASE submit a bug report to https://bugs.llvm.org/ and include the crash backtrace.
Stack dump:
0. Program arguments: ./llvm-project/build/bin/llc -mtriple=aarch64-eabi -aarch64-neon-syntax=generic
1. Running pass 'Function Pass Manager' on module '<stdin>'.
2. Running pass 'AArch64 Assembly Printer' on function '@add_B'
#0 0x00007f2bc94d2167 llvm::sys::PrintStackTrace(llvm::raw_ostream&) ./llvm-project/llvm/lib/Support/Unix/Signals.inc:564:11
#1 0x00007f2bc94d2309 PrintStackTraceSignalHandler(void*) ./llvm-project/llvm/lib/Support/Unix/Signals.inc:625:1
#2 0x00007f2bc94d0b1b llvm::sys::RunSignalHandlers() ./llvm-project/llvm/lib/Support/Signals.cpp:67:5
#3 0x00007f2bc94d2a55 SignalHandler(int) ./llvm-project/llvm/lib/Support/Unix/Signals.inc:406:1
#4 0x00007f2bc8695390 __restore_rt (/lib/x86_64-linux-gnu/libpthread.so.0+0x11390)
#5 0x00007f2bc79eb428 raise /build/glibc-LK5gWL/glibc-2.23/signal/../sysdeps/unix/sysv/linux/raise.c:54:0
#6 0x00007f2bc79ed02a abort /build/glibc-LK5gWL/glibc-2.23/stdlib/abort.c:91:0
#7 0x00007f2bc79e3bd7 __assert_fail_base /build/glibc-LK5gWL/glibc-2.23/assert/assert.c:92:0
#8 0x00007f2bc79e3c82 (/lib/x86_64-linux-gnu/libc.so.6+0x2dc82)
#9 0x00007f2bca6a1a2b llvm::MCInstPrinter::matchAliasPatterns(llvm::MCInst const*, llvm::MCSubtargetInfo const*, llvm::AliasMatchingData const&) ./llvm-project/llvm/lib/MC/MCInstPrinter.cpp:169:10
#10 0x00007f2bcd11b1be llvm::AArch64InstPrinter::printAliasInstr(llvm::MCInst const*, unsigned long, llvm::MCSubtargetInfo const&, llvm::raw_ostream&) ./llvm-project/build/lib/Target/AArch64/AArch64GenAsmWriter.inc:23456:15
#11 0x00007f2bcd12373c llvm::AArch64InstPrinter::printInst(llvm::MCInst const*, unsigned long, llvm::StringRef, llvm::MCSubtargetInfo const&, llvm::raw_ostream&) ./llvm-project/llvm/lib/Target/AArch64/MCTargetDesc/AArch64InstPrinter.cpp:298:7
#12 0x00007f2bca6c542f llvm::MCTargetStreamer::prettyPrintAsm(llvm::MCInstPrinter&, unsigned long, llvm::MCInst const&, llvm::MCSubtargetInfo const&, llvm::raw_ostream&) ./llvm-project/llvm/lib/MC/MCStreamer.cpp:979:1
#13 0x00007f2bca63d6b7 (anonymous namespace)::MCAsmStreamer::emitInstruction(llvm::MCInst const&, llvm::MCSubtargetInfo const&) ./llvm-project/llvm/lib/MC/MCAsmStreamer.cpp:1972:5
#14 0x00007f2bcbf60c8c llvm::AsmPrinter::EmitToStreamer(llvm::MCStreamer&, llvm::MCInst const&) ./llvm-project/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp:235:1
#15 0x00007f2bcdc9d3e2 (anonymous namespace)::AArch64AsmPrinter::emitInstruction(llvm::MachineInstr const*) ./llvm-project/llvm/lib/Target/AArch64/AArch64AsmPrinter.cpp:1317:1
#16 0x00007f2bcbf65689 llvm::AsmPrinter::emitFunctionBody() ./llvm-project/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp:1176:25
#17 0x00007f2bcdc9af09 (anonymous namespace)::AArch64AsmPrinter::runOnMachineFunction(llvm::MachineFunction&) ./llvm-project/llvm/lib/Target/AArch64/AArch64AsmPrinter.cpp:142:5
#18 0x00007f2bcb96bd17 llvm::MachineFunctionPass::runOnFunction(llvm::Function&) ./llvm-project/llvm/lib/CodeGen/MachineFunctionPass.cpp:73:8
#19 0x00007f2bcae2750c llvm::FPPassManager::runOnFunction(llvm::Function&) ./llvm-project/llvm/lib/IR/LegacyPassManager.cpp:1482:23
#20 0x00007f2bcae27935 llvm::FPPassManager::runOnModule(llvm::Module&) ./llvm-project/llvm/lib/IR/LegacyPassManager.cpp:1518:16
#21 0x00007f2bcae28094 (anonymous namespace)::MPPassManager::runOnModule(llvm::Module&) ./llvm-project/llvm/lib/IR/LegacyPassManager.cpp:1583:23
#22 0x00007f2bcae27bd8 llvm::legacy::PassManagerImpl::run(llvm::Module&) ./llvm-project/llvm/lib/IR/LegacyPassManager.cpp:1695:16
#23 0x00007f2bcae28631 llvm::legacy::PassManager::run(llvm::Module&) ./llvm-project/llvm/lib/IR/LegacyPassManager.cpp:1726:3
#24 0x000000000022237f compileModule(char**, llvm::LLVMContext&) ./llvm-project/llvm/tools/llc/llc.cpp:627:41
#25 0x00000000002208df main ./llvm-project/llvm/tools/llc/llc.cpp:360:13
#26 0x00007f2bc79d6830 __libc_start_main /build/glibc-LK5gWL/glibc-2.23/csu/../csu/libc-start.c:325:0
#27 0x0000000000220029 _start (./llvm-project/build/bin/llc+0x220029)
FileCheck error: '<stdin>' is empty.
FileCheck command line: ./llvm-project/build/bin/FileCheck ./llvm-project/llvm/test/CodeGen/AArch64/aarch64-addv.ll
--
I'm wondering if there is a better way to do this than the hack I came up with
or if this is a gap in InstAlias/TableGen?
Any ideas or thoughts would greatly appreciated.
Thanks,
Cullen
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