[llvm] [X86][MC] Report error when the instruction length exceeds 15 bytes (PR #83708)
Shengchen Kan via llvm-commits
llvm-commits at lists.llvm.org
Mon Mar 4 00:03:50 PST 2024
https://github.com/KanRobert updated https://github.com/llvm/llvm-project/pull/83708
>From 30893c5d1b65e8168584d0cdc6f41fcf61ea51f2 Mon Sep 17 00:00:00 2001
From: Shengchen Kan <shengchen.kan at intel.com>
Date: Sun, 3 Mar 2024 14:00:42 +0800
Subject: [PATCH 1/4] [X86][MC] Report error when the instruction length
exceeds 15 bytes
The instruction-size limit of 15 bytes still applies to APX
instructions.
Note that it is possible for an EVEX-encoded legacy instruction to reach
the 15-byte instruction length limit: 4
bytes of EVEX prefix + 1 byte of opcode + 1 byte of ModRM + 1 byte of
SIB + 4 bytes of displacement + 4 bytes of immediate = 15 bytes in total, e.g.
```
addq $184, -96, %rax # encoding:
[0x62,0xf4,0xfc,0x18,0x81,0x04,0x25,0xa0,0xff,0xff,0xff,0xb8,0x00,0x00,0x00]
```
If we added a segment prefix like fs, the length would be 16.
In such a case, no additional (ASIZE or segment override) prefix can be
used.
To help users find this issue earlier, we change the internal compiler
error to error in this patch.
---
.../X86/MCTargetDesc/X86MCCodeEmitter.cpp | 5 ++--
llvm/test/MC/X86/apx/long-instruction-err.s | 25 +++++++++++++++++++
2 files changed, 28 insertions(+), 2 deletions(-)
create mode 100644 llvm/test/MC/X86/apx/long-instruction-err.s
diff --git a/llvm/lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp b/llvm/lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp
index fdb11d1a408bb6..fd96a173af27e0 100644
--- a/llvm/lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp
+++ b/llvm/lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp
@@ -1924,8 +1924,9 @@ void X86MCCodeEmitter::encodeInstruction(const MCInst &MI,
if ((TSFlags & X86II::OpMapMask) == X86II::ThreeDNow)
emitByte(X86II::getBaseOpcodeFor(TSFlags), CB);
- assert(CB.size() - StartByte <= 15 &&
- "The size of instruction must be no longer than 15.");
+ if (CB.size() - StartByte > 15)
+ Ctx.reportError(MI.getLoc(),
+ "The size of instruction must be no longer than 15.");
#ifndef NDEBUG
// FIXME: Verify.
if (/*!Desc.isVariadic() &&*/ CurOp != NumOps) {
diff --git a/llvm/test/MC/X86/apx/long-instruction-err.s b/llvm/test/MC/X86/apx/long-instruction-err.s
new file mode 100644
index 00000000000000..a2210ecad81709
--- /dev/null
+++ b/llvm/test/MC/X86/apx/long-instruction-err.s
@@ -0,0 +1,25 @@
+# RUN: not llvm-mc -triple x86_64 -show-encoding %s 2>&1 | FileCheck %s
+
+# CHECK: error: The size of instruction must be no longer than 15.
+# CHECK: addq $1234, %cs:-96, %rax
+addq $1234, %cs:-96, %rax
+
+# CHECK: error: The size of instruction must be no longer than 15.
+# CHECK: subq $1234, %fs:257(%rbx, %rcx), %rax
+subq $1234, %fs:257(%rbx, %rcx), %rax
+
+# CHECK: error: The size of instruction must be no longer than 15.
+# CHECK: orq $1234, 257(%ebx, %ecx), %rax
+orq $1234, 257(%ebx, %ecx), %rax
+
+# CHECK: error: The size of instruction must be no longer than 15.
+# CHECK: xorq $1234, %gs:257(%ebx), %rax
+xorq $1234, %gs:257(%ebx), %rax
+
+# CHECK: error: The size of instruction must be no longer than 15.
+# CHECK: {nf} andq $1234, %cs:-96
+{nf} andq $1234, %cs:-96
+
+# CHECK: error: The size of instruction must be no longer than 15.
+# CHECK: {evex} adcq $1234, %cs:-96
+{evex} adcq $1234, %cs:-96
>From f3070ee30b4d5638283d79ac3cd50ea872d24679 Mon Sep 17 00:00:00 2001
From: Shengchen Kan <shengchen.kan at intel.com>
Date: Mon, 4 Mar 2024 10:44:33 +0800
Subject: [PATCH 2/4] address review comment: refine err message
---
llvm/lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/llvm/lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp b/llvm/lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp
index fd96a173af27e0..ba88b413890de1 100644
--- a/llvm/lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp
+++ b/llvm/lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp
@@ -1926,7 +1926,7 @@ void X86MCCodeEmitter::encodeInstruction(const MCInst &MI,
if (CB.size() - StartByte > 15)
Ctx.reportError(MI.getLoc(),
- "The size of instruction must be no longer than 15.");
+ "the size of instruction must be no longer than 15");
#ifndef NDEBUG
// FIXME: Verify.
if (/*!Desc.isVariadic() &&*/ CurOp != NumOps) {
>From 35c15f51987de99847cd621c601d052eb838fcb9 Mon Sep 17 00:00:00 2001
From: Shengchen Kan <shengchen.kan at intel.com>
Date: Mon, 4 Mar 2024 11:13:03 +0800
Subject: [PATCH 3/4] update test after err message is changed
---
llvm/test/MC/X86/apx/long-instruction-err.s | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/llvm/test/MC/X86/apx/long-instruction-err.s b/llvm/test/MC/X86/apx/long-instruction-err.s
index a2210ecad81709..4fb2b8beb1baf0 100644
--- a/llvm/test/MC/X86/apx/long-instruction-err.s
+++ b/llvm/test/MC/X86/apx/long-instruction-err.s
@@ -1,25 +1,25 @@
# RUN: not llvm-mc -triple x86_64 -show-encoding %s 2>&1 | FileCheck %s
-# CHECK: error: The size of instruction must be no longer than 15.
+# CHECK: error: the size of instruction must be no longer than 15
# CHECK: addq $1234, %cs:-96, %rax
addq $1234, %cs:-96, %rax
-# CHECK: error: The size of instruction must be no longer than 15.
+# CHECK: error: the size of instruction must be no longer than 15
# CHECK: subq $1234, %fs:257(%rbx, %rcx), %rax
subq $1234, %fs:257(%rbx, %rcx), %rax
-# CHECK: error: The size of instruction must be no longer than 15.
+# CHECK: error: the size of instruction must be no longer than 15
# CHECK: orq $1234, 257(%ebx, %ecx), %rax
orq $1234, 257(%ebx, %ecx), %rax
-# CHECK: error: The size of instruction must be no longer than 15.
+# CHECK: error: the size of instruction must be no longer than 15
# CHECK: xorq $1234, %gs:257(%ebx), %rax
xorq $1234, %gs:257(%ebx), %rax
-# CHECK: error: The size of instruction must be no longer than 15.
+# CHECK: error: the size of instruction must be no longer than 15
# CHECK: {nf} andq $1234, %cs:-96
{nf} andq $1234, %cs:-96
-# CHECK: error: The size of instruction must be no longer than 15.
+# CHECK: error: the size of instruction must be no longer than 15
# CHECK: {evex} adcq $1234, %cs:-96
{evex} adcq $1234, %cs:-96
>From e55d73b469c2b24bbb4e2c462d1ad98a226d98c7 Mon Sep 17 00:00:00 2001
From: Shengchen Kan <shengchen.kan at intel.com>
Date: Mon, 4 Mar 2024 16:02:40 +0800
Subject: [PATCH 4/4] Address review comments: align with binutils and test
file/line information
---
.../lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp | 3 +--
llvm/test/MC/X86/apx/long-instruction-err.s | 12 ++++++------
2 files changed, 7 insertions(+), 8 deletions(-)
diff --git a/llvm/lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp b/llvm/lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp
index ba88b413890de1..1fa676eeb79b0f 100644
--- a/llvm/lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp
+++ b/llvm/lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp
@@ -1925,8 +1925,7 @@ void X86MCCodeEmitter::encodeInstruction(const MCInst &MI,
emitByte(X86II::getBaseOpcodeFor(TSFlags), CB);
if (CB.size() - StartByte > 15)
- Ctx.reportError(MI.getLoc(),
- "the size of instruction must be no longer than 15");
+ Ctx.reportError(MI.getLoc(), "instruction length exceeds the limit of 15");
#ifndef NDEBUG
// FIXME: Verify.
if (/*!Desc.isVariadic() &&*/ CurOp != NumOps) {
diff --git a/llvm/test/MC/X86/apx/long-instruction-err.s b/llvm/test/MC/X86/apx/long-instruction-err.s
index 4fb2b8beb1baf0..966c6d893521a2 100644
--- a/llvm/test/MC/X86/apx/long-instruction-err.s
+++ b/llvm/test/MC/X86/apx/long-instruction-err.s
@@ -1,25 +1,25 @@
# RUN: not llvm-mc -triple x86_64 -show-encoding %s 2>&1 | FileCheck %s
-# CHECK: error: the size of instruction must be no longer than 15
+# CHECK: [[#@LINE+2]]:1: error: instruction length exceeds the limit of 15
# CHECK: addq $1234, %cs:-96, %rax
addq $1234, %cs:-96, %rax
-# CHECK: error: the size of instruction must be no longer than 15
+# CHECK: [[#@LINE+2]]:1: error: instruction length exceeds the limit of 15
# CHECK: subq $1234, %fs:257(%rbx, %rcx), %rax
subq $1234, %fs:257(%rbx, %rcx), %rax
-# CHECK: error: the size of instruction must be no longer than 15
+# CHECK: [[#@LINE+2]]:1: error: instruction length exceeds the limit of 15
# CHECK: orq $1234, 257(%ebx, %ecx), %rax
orq $1234, 257(%ebx, %ecx), %rax
-# CHECK: error: the size of instruction must be no longer than 15
+# CHECK: [[#@LINE+2]]:1: error: instruction length exceeds the limit of 15
# CHECK: xorq $1234, %gs:257(%ebx), %rax
xorq $1234, %gs:257(%ebx), %rax
-# CHECK: error: the size of instruction must be no longer than 15
+# CHECK: [[#@LINE+2]]:1: error: instruction length exceeds the limit of 15
# CHECK: {nf} andq $1234, %cs:-96
{nf} andq $1234, %cs:-96
-# CHECK: error: the size of instruction must be no longer than 15
+# CHECK: [[#@LINE+2]]:1: error: instruction length exceeds the limit of 15
# CHECK: {evex} adcq $1234, %cs:-96
{evex} adcq $1234, %cs:-96
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