When diffing disassembly dump of two binaries, I see lots of noises from mismatched jump target addresses and global data references, which unnecessarily causes diffs on every function, making it impractical. I'm trying to symbolize the raw binary addresses to minimize the diff noise.
In this change, a local branch target is modeled as a label and the branch target operand will simply be printed as a label. Local labels are collected by a separate pre-decoding pass beforehand. A global data memory operand will be printed as a global symbol instead of the raw data address. Unfortunately, due to the way the disassembler is set up and to be less intrusive, a global symbol is always printed as the last operand of a memory access instruction. This is less than ideal but is probably acceptable from checking code quality point of view since on most targets an instruction can have at most one memory operand.
So far only the X86 disassemblers are supported.
Test Plan:
llvm-objdump -d --x86-asm-syntax=intel --no-show-raw-insn --no-leading-addr :
```
Disassembly of section .text:
<_start>:
push rax
mov dword ptr [rsp + 4], 0
mov dword ptr [rsp], 0
mov eax, dword ptr [rsp]
cmp eax, dword ptr [rip + 4112] # 202182 <g>
jge 0x20117e <_start+0x25>
call 0x201158 <foo>
inc dword ptr [rsp]
jmp 0x201169 <_start+0x10>
xor eax, eax
pop rcx
ret
```
llvm-objdump -d **--symbolize-operands** --x86-asm-syntax=intel --no-show-raw-insn --no-leading-addr :
```
Disassembly of section .text:
<_start>:
push rax
mov dword ptr [rsp + 4], 0
mov dword ptr [rsp], 0
<L1>:
mov eax, dword ptr [rsp]
cmp eax, dword ptr <g>
jge <L0>
call <foo>
inc dword ptr [rsp]
jmp <L1>
<L0>:
xor eax, eax
pop rcx
ret
```
Note that the jump instructions like `jge 0x20117e <_start+0x25>` without this work is printed as a real target address and an offset from the leading symbol. With a change in the optimizer that adds/deletes an instruction, the address and offset may shift for targets placed after the instruction. This will be a problem when diffing the disassembly from two optimizers where there are unnecessary false positives due to such branch target address changes. With `--symbolize-operand`, a label is printed for a branch target instead to reduce the false positives. Similarly, the disassemble of PC-relative global variable references is also prone to instruction insertion/deletion.
Reviewed By: jhenderson, MaskRay
Differential Revision: https://reviews.llvm.org/D84191
This patch implements initial backend support for a -mtune CPU controlled by a "tune-cpu" function attribute. If the attribute is not present X86 will use the resolved CPU from target-cpu attribute or command line.
This patch adds MC layer support a tune CPU. Each CPU now has two sets of features stored in their GenSubtargetInfo.inc tables . These features lists are passed separately to the Processor and ProcessorModel classes in tablegen. The tune list defaults to an empty list to avoid changes to non-X86. This annoyingly increases the size of static tables on all target as we now store 24 more bytes per CPU. I haven't quantified the overall impact, but I can if we're concerned.
One new test is added to X86 to show a few tuning features with mismatched tune-cpu and target-cpu/target-feature attributes to demonstrate independent control. Another new test is added to demonstrate that the scheduler model follows the tune CPU.
I have not added a -mtune to llc/opt or MC layer command line yet. With no attributes we'll just use the -mcpu for both. MC layer tools will always follow the normal CPU for tuning.
Differential Revision: https://reviews.llvm.org/D85165
These prefixes should override the default behavior and force a larger immediate size. I don't believe gas issues any warning if you use {disp8} when a 32-bit displacement is already required. And this patch doesn't either.
This completes the {disp8} and {disp32} support from PR46650.
Reviewed By: RKSimon
Differential Revision: https://reviews.llvm.org/D84793
By repeating the Disp.isImm() check in a couple spots we can
make the normal case for immediate and for expression the same.
And then always rely on the ForceDisp32 flag to remove a later
non-zero immediate check.
This should make {disp32} pseudo prefix handling
slightly easier as we need the normal disp32 handler to handle a
immediate of 0.
We currently handle EVEX and non-EVEX separately in two places. By sinking the EVEX
check into the existing helper for CDisp8 we can simplify these two places.
Differential Revision: https://reviews.llvm.org/D84730
In 16-bit mode we can encode a 32-bit address using 0x67 prefix.
We were failing to do this when the index register was a 32-bit
register, the base register was not present, and the displacement
fit in 16-bits.
Fixes PR46866.
ParseX86Triple already checks for 64-bit mode and produces a
static string. We can just add +sse2 to the end of that static
string. This avoids a potential reallocation when appending it
to the std::string at runtime.
This is a slight change to the behavior of tools that only use
MC layer which weren't implicitly enabling sse2 before, but will
now. I don't think we check for sse2 explicitly in any MC layer
components so this shouldn't matter in practice. And if it did
matter the new behavior is more correct.
The input to these functions is a StringRef. We then convert it
to a std::string. Then maybe replace with "generic". I think we
can just overwrite the incoming StringRef with "generic" if needed
and then pass it along without creating any std::string.
These are documented as using modrm byte of 0xe8, 0xf0, and 0xf8
respectively. But hardware ignore bits 2:0. So 0xe9-0xef is treated
the same as 0xe8. Similar for the other two.
Fixing this required adding 8 new formats to the X86 instructions
to convey this information. Could have gotten away with 3, but
adding all 8 made for a more logical conversion from format to
modrm encoding.
I renumbered the format encodings to keep the register modrm
formats grouped together.
Most of the wrappers exist to print the memory size in Intel syntax
and then call the printMemReference. But printanymem/printopaquemem
don't print anything extra in Intel syntax so just drop them.
Negations are incorrectly added in numerous places and the code just happens to work.
Also fix a missed DW_CFA_def_cfa_offset negation in c693b9c321d5a40d012340619674cf790c9ac86c:
ARMAsmBackendDarwin::generateCompactUnwindEncoding
The generic implementation is actually specific to x86. It assumes the
offset is relative to the end of the instruction and the immediate is
not scaled (which is false on most RISC).
Summary:
Before this patch, `relaxInstruction` takes three arguments, the first
argument refers to the instruction before relaxation and the third
argument is the output instruction after relaxation. There are two quite
strange things:
1) The first argument's type is `const MCInst &`, the third
argument's type is `MCInst &`, but they may be aliased to the same
variable
2) The backends of ARM, AMDGPU, RISC-V, Hexagon assume that the third
argument is a fresh uninitialized `MCInst` even if `relaxInstruction`
may be called like `relaxInstruction(Relaxed, STI, Relaxed)` in a
loop.
In this patch, we drop the thrid argument, and let `relaxInstruction`
directly modify the given instruction. Also, this patch fixes the bug https://bugs.llvm.org/show_bug.cgi?id=45580, which is introduced by D77851, and
breaks the assumption of ARM, AMDGPU, RISC-V, Hexagon.
Reviewers: Razer6, MaskRay, jyknight, asb, luismarques, enderby, rtaylor, colinl, bcain
Reviewed By: Razer6, MaskRay, bcain
Subscribers: bcain, nickdesaulniers, nathanchance, wuzish, annita.zhang, arsenm, dschuff, jyknight, dylanmckay, sdardis, nemanjai, jvesely, nhaehnle, tpr, sbc100, jgravelle-google, kristof.beyls, hiraditya, aheejin, kbarton, fedor.sergeev, asb, rbar, johnrusso, simoncook, sabuasal, niosHD, jrtc27, MaskRay, zzheng, edward-jones, atanasyan, rogfer01, MartinMosbeck, brucehoult, the_o, PkmX, jocewei, Jim, lenary, s.egerton, pzheng, sameer.abuasal, apazos, luismarques, kerbowa, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D78364
We don't need all of MCStreamer.h, just FormattedStream.h. The rest can be replaced with forward declarations.
X86WinAllocaExpander.cpp had an implicit dependency on MapVector.h which I've added locally.
Summary:
When we encode an instruction, we need to know the number of bytes being
emitted to determine the fixups in `X86MCCodeEmitter::emitImmediate`.
There are only two callers for `emitImmediate`: `emitMemModRMByte` and
`encodeInstruction`.
Before this patch, we kept track of the current byte being emitted
by passing a reference parameter `CurByte` across all the `emit*`
funtions, which is ugly and unnecessary. For example, we don't have any
fixups when emitting prefixes, so we don't need to track this value.
In this patch, we use `StartByte` to record the initial status of the
streamer, and use `OS.tell()` to get the current status of the streamer
when we need to know the number of bytes being emitted. On one hand,
this eliminates the parameter `CurByte` for most `emit*` functions, on
the other hand, this make things clear: Only pass the parameter when we
really need it.
Reviewers: craig.topper, pengfei, MaskRay
Reviewed By: craig.topper, MaskRay
Subscribers: hiraditya, llvm-commits, annita.zhang
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D78419
Summary:
The instruction in non-text section can not be executed, so they will not affect performance.
In addition, their encoding values are treated as data, so we should not touch them.
Reviewers: MaskRay, reames, LuoYuanke, jyknight
Reviewed By: MaskRay
Subscribers: annita.zhang, hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D77971
Previous patch didn't handle the early return in `emitREXPrefix` correctly,
which causes REX prefix was not emitted for instruction without
operands. This patch includes the fix for that.
Summary:
We determine the REX prefix used by instruction in `determineREXPrefix`,
and this value is used in `emitMemModRMByte' and used as the return
value of `emitOpcodePrefix`.
Before this patch, REX was passed as reference to `emitPrefixImpl`, it
is strange and not necessary, e.g, we have to write
```
bool Rex = false;
emitPrefixImpl(CurOp, CurByte, Rex, MI, STI, OS);
```
in `emitPrefix` even if `Rex` will not be used.
So we let HasREX be the return value of `emitPrefixImpl`. The HasREX is passed
from `emitREXPrefix` to `emitOpcodePrefix` and then to
`emitPrefixImpl`. This makes sense since REX is a kind of opcode prefix
and of course is a prefix.
Reviewers: craig.topper, pengfei
Reviewed By: craig.topper
Subscribers: annita.zhang, craig.topper, hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D78276
Summary:
The function in X86MCCodeEmitter has too many parameters to make it look
messy, and some parameters are unnecessary. This is the first patch to
reduce their parameters.
The follwing operations are cheap
```
unsigned Opcode = MI.getOpcode();
const MCInstrDesc &Desc = MCII.get(Opcode);
uint64_t TSFlags = Desc.TSFlags;
```
So if we pass a `MCInst`, we don't need to pass `MCInstrDesc`;
if we pass a `MCInstrDesc`, we don't need to pass `TSFlags`.
Reviewers: craig.topper, MaskRay, pengfei
Reviewed By: craig.topper
Subscribers: annita.zhang, hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D78180
The shuffle decoding is used by X86ISelLowering and
MCTargetDesc/X86InstComments. The latter used to be in a
separate InstPrinter library. The Utils library existed to allow
InstPrinter and CodeGen to share the shuffle decoding. Since
X86InstComments now lives in the MCTargetDesc, which CodeGen
already depends on, we can sink the shuffle decoding there as well.
Differential Revision: https://reviews.llvm.org/D77980
Summary:
Since D75300 has been landed, I want to support enhanced relaxation when we need to align branches and allow prefix padding. "Enhanced Relaxtion" means we allow an instruction that could not be traditionally relaxed to be emitted into RelaxableFragment so that we increase its length by adding prefixes for optimization.
The motivation is straightforward, RelaxFragment is mostly for relative jumps and we can not increase the length of jumps when we need to align them, so if we need to achieve D75300's purpose (reducing the bytes of nops) when need to align jumps, we have to make more instructions "relaxable".
Reviewers: reames, MaskRay, craig.topper, LuoYuanke, jyknight
Reviewed By: reames
Subscribers: hiraditya, llvm-commits, annita.zhang
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D76286
Generalizes D62014 (R_386_NONE/R_X86_64_NONE).
Unlike ARM (D76746) and AArch64 (D76754), we cannot delete FK_NONE from
getFixupKindSize because FK_NONE is still used by R_386_TLS_DESC_CALL/R_X86_64_TLSDESC_CALL.
Simon Pilgrim