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[AMDGPU] Improve disassembler error handling

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Summary:
llvm-objdump now disassembles unrecognised opcodes as data, using
the .long directive. We treat unrecognised opcodes as being 32 bit
values, so move along 4 bytes rather than the single byte which
previously resulted in a cascade of bogus disassembly following an
unrecognised opcode.

While no solution can always disassemble code that contains
embedded data correctly this provides a significant improvement.

The disassembler will now cope with an arbitrary length section
as it no longer truncates it to a multiple of 4 bytes, and will
use the .byte directive for trailing bytes.

Subscribers: arsenm, kzhuravl, wdng, nhaehnle, yaxunl, dstuttard, tpr, t-tye, llvm-commits

Differential Revision: https://reviews.llvm.org/D44685

llvm-svn: 328553
This commit is contained in:
Tim Corringham 2018-03-26 17:06:33 +00:00
parent f8bc7da8ea
commit 6c9d475041
3 changed files with 65 additions and 18 deletions
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5
lib/Target/AMDGPU/Disassembler/AMDGPUDisassembler.cpp
View File

@ -246,7 +246,10 @@ DecodeStatus AMDGPUDisassembler::getInstruction(MCInst &MI, uint64_t &Size,
if (Res && IsSDWA)
Res = convertSDWAInst(MI);
Size = Res ? (MaxInstBytesNum - Bytes.size()) : 0;
// if the opcode was not recognized we'll assume a Size of 4 bytes
// (unless there are fewer bytes left)
Size = Res ? (MaxInstBytesNum - Bytes.size())
: std::min((size_t)4, Bytes_.size());
return Res;
}

27
test/MC/AMDGPU/data.s Normal file
View File

@ -0,0 +1,27 @@
// We check that unrecognized opcodes are disassembled by llvm-objdump as data using the .long directive
// and any trailing bytes are disassembled using the .byte directive
// RUN: llvm-mc -filetype=obj -triple=amdgcn--amdpal -mcpu=gfx900 -show-encoding %s | llvm-objdump -disassemble -mcpu=gfx900 - | FileCheck %s
.text
v_mov_b32 v7, s24
v_mov_b32 v8, s25
.long 0xabadc0de
s_nop 0
s_endpgm
.long 0xbadc0de1, 0xbadc0de2, 0xbadc0de3, 0xbadc0de4
.byte 0x0a, 0x0b
.byte 0x0c
// CHECK: .text
// CHECK: v_mov_b32
// CHECK: v_mov_b32
// CHECK: .long 0xabadc0de
// CHECK_SAME: : ABADC0DE
// CHECK: s_endpgm
// CHECK: .long 0xbadc0de1
// CHECK: .long 0xbadc0de2
// CHECK: .long 0xbadc0de3
// CHECK: .long 0xbadc0de4
// CHECK: .byte 0x0a, 0x0b, 0x0c
// CHECK-SAME: : 0A 0B 0C
// CHECK-NOT: .long

51
tools/llvm-objdump/llvm-objdump.cpp
View File

@ -595,23 +595,42 @@ public:
if (SP && (PrintSource || PrintLines))
SP->printSourceLine(OS, Address);
if (!MI) {
OS << " <unknown>";
return;
typedef support::ulittle32_t U32;
if (MI) {
SmallString<40> InstStr;
raw_svector_ostream IS(InstStr);
IP.printInst(MI, IS, "", STI);
OS << left_justify(IS.str(), 60);
} else {
// an unrecognized encoding - this is probably data so represent it
// using the .long directive, or .byte directive if fewer than 4 bytes
// remaining
if (Bytes.size() >= 4) {
OS << format("\t.long 0x%08" PRIx32 " ",
static_cast<uint32_t>(*reinterpret_cast<const U32*>(Bytes.data())));
OS.indent(42);
} else {
OS << format("\t.byte 0x%02" PRIx8, Bytes[0]);
for (unsigned int i = 1; i < Bytes.size(); i++)
OS << format(", 0x%02" PRIx8, Bytes[i]);
OS.indent(55 - (6 * Bytes.size()));
}
}
SmallString<40> InstStr;
raw_svector_ostream IS(InstStr);
IP.printInst(MI, IS, "", STI);
OS << left_justify(IS.str(), 60) << format("// %012" PRIX64 ": ", Address);
typedef support::ulittle32_t U32;
for (auto D : makeArrayRef(reinterpret_cast<const U32*>(Bytes.data()),
Bytes.size() / sizeof(U32)))
// D should be explicitly casted to uint32_t here as it is passed
// by format to snprintf as vararg.
OS << format("%08" PRIX32 " ", static_cast<uint32_t>(D));
OS << format("// %012" PRIX64 ": ", Address);
if (Bytes.size() >=4) {
for (auto D : makeArrayRef(reinterpret_cast<const U32*>(Bytes.data()),
Bytes.size() / sizeof(U32)))
// D should be explicitly casted to uint32_t here as it is passed
// by format to snprintf as vararg.
OS << format("%08" PRIX32 " ", static_cast<uint32_t>(D));
} else {
for (unsigned int i = 0; i < Bytes.size(); i++)
OS << format("%02" PRIX8 " ", Bytes[i]);
}
if (!Annot.empty())
OS << "// " << Annot;
@ -1459,8 +1478,6 @@ static void DisassembleObject(const ObjectFile *Obj, bool InlineRelocs) {
End = StopAddress - SectionAddr;
if (Obj->isELF() && Obj->getArch() == Triple::amdgcn) {
// make size 4 bytes folded
End = Start + ((End - Start) & ~0x3ull);
if (std::get<2>(Symbols[si]) == ELF::STT_AMDGPU_HSA_KERNEL) {
// skip amd_kernel_code_t at the begining of kernel symbol (256 bytes)
Start += 256;