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[X86] Emit REX prefix immediately before the opcode
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Fix prefix emission order to emit REX immediately before the opcode (SDM vol2,
2.1, Figure 2-1). According to SDM vol2 2.2.1, "Other placements are ignored".

This fix has a side effect of outputting segment override prefix in a different
order than previously (benign).

Follow-up to https://reviews.llvm.org/D120592

Reviewed By: skan, craig.topper

Differential Revision: https://reviews.llvm.org/D120871
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@aaupov
aaupov committed Mar 16, 2022
1 parent 1d37198 commit 2c4e38f
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Showing 11 changed files with 78 additions and 77 deletions.
17 changes: 9 additions & 8 deletions llvm/lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -617,14 +617,6 @@ bool X86MCCodeEmitter::emitPrefixImpl(unsigned &CurOp, const MCInst &MI,
Flags & X86::IP_HAS_AD_SIZE)
emitByte(0x67, OS);

// Encoding type for this instruction.
uint64_t Encoding = TSFlags & X86II::EncodingMask;
bool HasREX = false;
if (Encoding)
emitVEXOpcodePrefix(MemoryOperand, MI, OS);
else
HasREX = emitOpcodePrefix(MemoryOperand, MI, STI, OS);

uint64_t Form = TSFlags & X86II::FormMask;
switch (Form) {
default:
Expand Down Expand Up @@ -654,6 +646,15 @@ bool X86MCCodeEmitter::emitPrefixImpl(unsigned &CurOp, const MCInst &MI,
}
}

// REX prefix is optional, but if used must be immediately before the opcode
// Encoding type for this instruction.
uint64_t Encoding = TSFlags & X86II::EncodingMask;
bool HasREX = false;
if (Encoding)
emitVEXOpcodePrefix(MemoryOperand, MI, OS);
else
HasREX = emitOpcodePrefix(MemoryOperand, MI, STI, OS);

return HasREX;
}

Expand Down
12 changes: 6 additions & 6 deletions llvm/test/MC/Disassembler/X86/moffs.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -37,9 +37,9 @@
# 64: movw 0x5a5a5a5a, %ax # encoding: [0x67,0x66,0xa1,0x5a,0x5a,0x5a,0x5a]
0x67 0x66 0xa1 0x5a 0x5a 0x5a 0x5a 0x5a 0x5a 0x5a 0x5a

# 16: movl %es:0x5a5a5a5a, %eax # encoding: [0x67,0x66,0x26,0xa1,0x5a,0x5a,0x5a,0x5a]
# 32: movw %es:0x5a5a, %ax # encoding: [0x67,0x66,0x26,0xa1,0x5a,0x5a]
# 64: movw %es:0x5a5a5a5a, %ax # encoding: [0x67,0x66,0x26,0xa1,0x5a,0x5a,0x5a,0x5a]
# 16: movl %es:0x5a5a5a5a, %eax # encoding: [0x67,0x26,0x66,0xa1,0x5a,0x5a,0x5a,0x5a]
# 32: movw %es:0x5a5a, %ax # encoding: [0x67,0x26,0x66,0xa1,0x5a,0x5a]
# 64: movw %es:0x5a5a5a5a, %ax # encoding: [0x67,0x26,0x66,0xa1,0x5a,0x5a,0x5a,0x5a]
0x67 0x26 0x66 0xa1 0x5a 0x5a 0x5a 0x5a 0x5a 0x5a 0x5a 0x5a # encoding: [0xa0,0x5a,0x5a]


Expand Down Expand Up @@ -79,8 +79,8 @@
# 64: movw %ax, 0x5a5a5a5a # encoding: [0x67,0x66,0xa3,0x5a,0x5a,0x5a,0x5a]
0x67 0x66 0xa3 0x5a 0x5a 0x5a 0x5a 0x5a 0x5a 0x5a 0x5a

# 16: movl %eax, %es:0x5a5a5a5a # encoding: [0x67,0x66,0x26,0xa3,0x5a,0x5a,0x5a,0x5a]
# 32: movw %ax, %es:0x5a5a # encoding: [0x67,0x66,0x26,0xa3,0x5a,0x5a]
# 64: movw %ax, %es:0x5a5a5a5a # encoding: [0x67,0x66,0x26,0xa3,0x5a,0x5a,0x5a,0x5a]
# 16: movl %eax, %es:0x5a5a5a5a # encoding: [0x67,0x26,0x66,0xa3,0x5a,0x5a,0x5a,0x5a]
# 32: movw %ax, %es:0x5a5a # encoding: [0x67,0x26,0x66,0xa3,0x5a,0x5a]
# 64: movw %ax, %es:0x5a5a5a5a # encoding: [0x67,0x26,0x66,0xa3,0x5a,0x5a,0x5a,0x5a]
0x67 0x26 0x66 0xa3 0x5a 0x5a 0x5a 0x5a 0x5a 0x5a 0x5a 0x5a

6 changes: 3 additions & 3 deletions llvm/test/MC/X86/I186-32.s
View file
Original file line number Diff line number Diff line change
Expand Up @@ -57,7 +57,7 @@ outsb %es:(%esi), %dx
outsl %es:(%esi), %dx

// CHECK: outsw %es:(%esi), %dx
// CHECK: encoding: [0x66,0x26,0x6f]
// CHECK: encoding: [0x26,0x66,0x6f]
outsw %es:(%esi), %dx

// CHECK: popal
Expand Down Expand Up @@ -269,7 +269,7 @@ repne outsb %es:(%esi), %dx
repne outsl %es:(%esi), %dx

// CHECK: repne outsw %es:(%esi), %dx
// CHECK: encoding: [0xf2,0x66,0x26,0x6f]
// CHECK: encoding: [0xf2,0x26,0x66,0x6f]
repne outsw %es:(%esi), %dx

// CHECK: rep outsb %es:(%esi), %dx
Expand All @@ -281,7 +281,7 @@ rep outsb %es:(%esi), %dx
rep outsl %es:(%esi), %dx

// CHECK: rep outsw %es:(%esi), %dx
// CHECK: encoding: [0xf3,0x66,0x26,0x6f]
// CHECK: encoding: [0xf3,0x26,0x66,0x6f]
rep outsw %es:(%esi), %dx

// CHECK: rolb $0, -485498096(%edx,%eax,4)
Expand Down
6 changes: 3 additions & 3 deletions llvm/test/MC/X86/I186-64.s
View file
Original file line number Diff line number Diff line change
Expand Up @@ -33,7 +33,7 @@ outsb %gs:(%rsi), %dx
outsl %gs:(%rsi), %dx

// CHECK: outsw %gs:(%rsi), %dx
// CHECK: encoding: [0x66,0x65,0x6f]
// CHECK: encoding: [0x65,0x66,0x6f]
outsw %gs:(%rsi), %dx

// CHECK: pushq $0
Expand Down Expand Up @@ -289,7 +289,7 @@ repne outsb %gs:(%rsi), %dx
repne outsl %gs:(%rsi), %dx

// CHECK: repne outsw %gs:(%rsi), %dx
// CHECK: encoding: [0xf2,0x66,0x65,0x6f]
// CHECK: encoding: [0xf2,0x65,0x66,0x6f]
repne outsw %gs:(%rsi), %dx

// CHECK: rep outsb %gs:(%rsi), %dx
Expand All @@ -301,7 +301,7 @@ rep outsb %gs:(%rsi), %dx
rep outsl %gs:(%rsi), %dx

// CHECK: rep outsw %gs:(%rsi), %dx
// CHECK: encoding: [0xf3,0x66,0x65,0x6f]
// CHECK: encoding: [0xf3,0x65,0x66,0x6f]
rep outsw %gs:(%rsi), %dx

// CHECK: rolb $0, 485498096
Expand Down
18 changes: 9 additions & 9 deletions llvm/test/MC/X86/I386-32.s
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Original file line number Diff line number Diff line change
Expand Up @@ -153,7 +153,7 @@ cmpsb %es:(%edi), %es:(%esi)
cmpsl %es:(%edi), %es:(%esi)

// CHECK: cmpsw %es:(%edi), %es:(%esi)
// CHECK: encoding: [0x66,0x26,0xa7]
// CHECK: encoding: [0x26,0x66,0xa7]
cmpsw %es:(%edi), %es:(%esi)

// CHECK: insb %dx, %es:(%edi)
Expand Down Expand Up @@ -193,7 +193,7 @@ movsb %es:(%esi), %es:(%edi)
movsl %es:(%esi), %es:(%edi)

// CHECK: movsw %es:(%esi), %es:(%edi)
// CHECK: encoding: [0x66,0x26,0xa5]
// CHECK: encoding: [0x26,0x66,0xa5]
movsw %es:(%esi), %es:(%edi)

// CHECK: outsb %es:(%esi), %dx
Expand All @@ -205,7 +205,7 @@ outsb %es:(%esi), %dx
outsl %es:(%esi), %dx

// CHECK: outsw %es:(%esi), %dx
// CHECK: encoding: [0x66,0x26,0x6f]
// CHECK: encoding: [0x26,0x66,0x6f]
outsw %es:(%esi), %dx

// CHECK: popal
Expand Down Expand Up @@ -249,7 +249,7 @@ rep cmpsb %es:(%edi), %es:(%esi)
rep cmpsl %es:(%edi), %es:(%esi)

// CHECK: rep cmpsw %es:(%edi), %es:(%esi)
// CHECK: encoding: [0xf3,0x66,0x26,0xa7]
// CHECK: encoding: [0xf3,0x26,0x66,0xa7]
rep cmpsw %es:(%edi), %es:(%esi)

// CHECK: rep insb %dx, %es:(%edi)
Expand Down Expand Up @@ -277,7 +277,7 @@ rep movsb %es:(%esi), %es:(%edi)
rep movsl %es:(%esi), %es:(%edi)

// CHECK: rep movsw %es:(%esi), %es:(%edi)
// CHECK: encoding: [0xf3,0x66,0x26,0xa5]
// CHECK: encoding: [0xf3,0x26,0x66,0xa5]
rep movsw %es:(%esi), %es:(%edi)

// CHECK: repne cmpsb %es:(%edi), %es:(%esi)
Expand All @@ -289,7 +289,7 @@ repne cmpsb %es:(%edi), %es:(%esi)
repne cmpsl %es:(%edi), %es:(%esi)

// CHECK: repne cmpsw %es:(%edi), %es:(%esi)
// CHECK: encoding: [0xf2,0x66,0x26,0xa7]
// CHECK: encoding: [0xf2,0x26,0x66,0xa7]
repne cmpsw %es:(%edi), %es:(%esi)

// CHECK: repne insb %dx, %es:(%edi)
Expand Down Expand Up @@ -317,7 +317,7 @@ repne movsb %es:(%esi), %es:(%edi)
repne movsl %es:(%esi), %es:(%edi)

// CHECK: repne movsw %es:(%esi), %es:(%edi)
// CHECK: encoding: [0xf2,0x66,0x26,0xa5]
// CHECK: encoding: [0xf2,0x26,0x66,0xa5]
repne movsw %es:(%esi), %es:(%edi)

// CHECK: repne outsb %es:(%esi), %dx
Expand All @@ -329,7 +329,7 @@ repne outsb %es:(%esi), %dx
repne outsl %es:(%esi), %dx

// CHECK: repne outsw %es:(%esi), %dx
// CHECK: encoding: [0xf2,0x66,0x26,0x6f]
// CHECK: encoding: [0xf2,0x26,0x66,0x6f]
repne outsw %es:(%esi), %dx

// CHECK: repne scasl %es:(%edi), %eax
Expand All @@ -349,7 +349,7 @@ rep outsb %es:(%esi), %dx
rep outsl %es:(%esi), %dx

// CHECK: rep outsw %es:(%esi), %dx
// CHECK: encoding: [0xf3,0x66,0x26,0x6f]
// CHECK: encoding: [0xf3,0x26,0x66,0x6f]
rep outsw %es:(%esi), %dx

// CHECK: rep scasl %es:(%edi), %eax
Expand Down
30 changes: 15 additions & 15 deletions llvm/test/MC/X86/I386-64.s
View file
Original file line number Diff line number Diff line change
Expand Up @@ -226,11 +226,11 @@ cmpsb %es:(%rdi), %gs:(%rsi)
cmpsl %es:(%rdi), %gs:(%rsi)

// CHECK: cmpsq %es:(%rdi), %gs:(%rsi)
// CHECK: encoding: [0x48,0x65,0xa7]
// CHECK: encoding: [0x65,0x48,0xa7]
cmpsq %es:(%rdi), %gs:(%rsi)

// CHECK: cmpsw %es:(%rdi), %gs:(%rsi)
// CHECK: encoding: [0x66,0x65,0xa7]
// CHECK: encoding: [0x65,0x66,0xa7]
cmpsw %es:(%rdi), %gs:(%rsi)

// CHECK: insb %dx, %es:(%rdi)
Expand Down Expand Up @@ -306,11 +306,11 @@ movsbl (%rdx), %r13d
movsl %gs:(%rsi), %es:(%rdi)

// CHECK: movsq %gs:(%rsi), %es:(%rdi)
// CHECK: encoding: [0x48,0x65,0xa5]
// CHECK: encoding: [0x65,0x48,0xa5]
movsq %gs:(%rsi), %es:(%rdi)

// CHECK: movsw %gs:(%rsi), %es:(%rdi)
// CHECK: encoding: [0x66,0x65,0xa5]
// CHECK: encoding: [0x65,0x66,0xa5]
movsw %gs:(%rsi), %es:(%rdi)

// CHECK: movswl 485498096, %r13d
Expand Down Expand Up @@ -418,7 +418,7 @@ outsb %gs:(%rsi), %dx
outsl %gs:(%rsi), %dx

// CHECK: outsw %gs:(%rsi), %dx
// CHECK: encoding: [0x66,0x65,0x6f]
// CHECK: encoding: [0x65,0x66,0x6f]
outsw %gs:(%rsi), %dx

// CHECK: rep cmpsb %es:(%rdi), %gs:(%rsi)
Expand All @@ -430,11 +430,11 @@ rep cmpsb %es:(%rdi), %gs:(%rsi)
rep cmpsl %es:(%rdi), %gs:(%rsi)

// CHECK: rep cmpsq %es:(%rdi), %gs:(%rsi)
// CHECK: encoding: [0xf3,0x48,0x65,0xa7]
// CHECK: encoding: [0xf3,0x65,0x48,0xa7]
rep cmpsq %es:(%rdi), %gs:(%rsi)

// CHECK: rep cmpsw %es:(%rdi), %gs:(%rsi)
// CHECK: encoding: [0xf3,0x66,0x65,0xa7]
// CHECK: encoding: [0xf3,0x65,0x66,0xa7]
rep cmpsw %es:(%rdi), %gs:(%rsi)

// CHECK: rep insb %dx, %es:(%rdi)
Expand Down Expand Up @@ -462,11 +462,11 @@ rep movsb %gs:(%rsi), %es:(%rdi)
rep movsl %gs:(%rsi), %es:(%rdi)

// CHECK: rep movsq %gs:(%rsi), %es:(%rdi)
// CHECK: encoding: [0xf3,0x48,0x65,0xa5]
// CHECK: encoding: [0xf3,0x65,0x48,0xa5]
rep movsq %gs:(%rsi), %es:(%rdi)

// CHECK: rep movsw %gs:(%rsi), %es:(%rdi)
// CHECK: encoding: [0xf3,0x66,0x65,0xa5]
// CHECK: encoding: [0xf3,0x65,0x66,0xa5]
rep movsw %gs:(%rsi), %es:(%rdi)

// CHECK: repne cmpsb %es:(%rdi), %gs:(%rsi)
Expand All @@ -478,11 +478,11 @@ repne cmpsb %es:(%rdi), %gs:(%rsi)
repne cmpsl %es:(%rdi), %gs:(%rsi)

// CHECK: repne cmpsq %es:(%rdi), %gs:(%rsi)
// CHECK: encoding: [0xf2,0x48,0x65,0xa7]
// CHECK: encoding: [0xf2,0x65,0x48,0xa7]
repne cmpsq %es:(%rdi), %gs:(%rsi)

// CHECK: repne cmpsw %es:(%rdi), %gs:(%rsi)
// CHECK: encoding: [0xf2,0x66,0x65,0xa7]
// CHECK: encoding: [0xf2,0x65,0x66,0xa7]
repne cmpsw %es:(%rdi), %gs:(%rsi)

// CHECK: repne insb %dx, %es:(%rdi)
Expand Down Expand Up @@ -510,11 +510,11 @@ repne movsb %gs:(%rsi), %es:(%rdi)
repne movsl %gs:(%rsi), %es:(%rdi)

// CHECK: repne movsq %gs:(%rsi), %es:(%rdi)
// CHECK: encoding: [0xf2,0x48,0x65,0xa5]
// CHECK: encoding: [0xf2,0x65,0x48,0xa5]
repne movsq %gs:(%rsi), %es:(%rdi)

// CHECK: repne movsw %gs:(%rsi), %es:(%rdi)
// CHECK: encoding: [0xf2,0x66,0x65,0xa5]
// CHECK: encoding: [0xf2,0x65,0x66,0xa5]
repne movsw %gs:(%rsi), %es:(%rdi)

// CHECK: repne outsb %gs:(%rsi), %dx
Expand All @@ -526,7 +526,7 @@ repne outsb %gs:(%rsi), %dx
repne outsl %gs:(%rsi), %dx

// CHECK: repne outsw %gs:(%rsi), %dx
// CHECK: encoding: [0xf2,0x66,0x65,0x6f]
// CHECK: encoding: [0xf2,0x65,0x66,0x6f]
repne outsw %gs:(%rsi), %dx

// CHECK: repne scasl %es:(%rdi), %eax
Expand All @@ -546,7 +546,7 @@ rep outsb %gs:(%rsi), %dx
rep outsl %gs:(%rsi), %dx

// CHECK: rep outsw %gs:(%rsi), %dx
// CHECK: encoding: [0xf3,0x66,0x65,0x6f]
// CHECK: encoding: [0xf3,0x65,0x66,0x6f]
rep outsw %gs:(%rsi), %dx

// CHECK: rep scasl %es:(%rdi), %eax
Expand Down
18 changes: 9 additions & 9 deletions llvm/test/MC/X86/I86-32.s
View file
Original file line number Diff line number Diff line change
Expand Up @@ -565,7 +565,7 @@ cmpsb %es:(%edi), %es:(%esi)
cmpsl %es:(%edi), %es:(%esi)

// CHECK: cmpsw %es:(%edi), %es:(%esi)
// CHECK: encoding: [0x66,0x26,0xa7]
// CHECK: encoding: [0x26,0x66,0xa7]
cmpsw %es:(%edi), %es:(%esi)

// CHECK: cmpw $0, -485498096(%edx,%eax,4)
Expand Down Expand Up @@ -1197,7 +1197,7 @@ lock xchgl %eax, (%edx)
lodsb %es:(%esi), %al

// CHECK: lodsw %es:(%esi), %ax
// CHECK: encoding: [0x66,0x26,0xad]
// CHECK: encoding: [0x26,0x66,0xad]
lodsw %es:(%esi), %ax

// CHECK: loop 64
Expand Down Expand Up @@ -1345,7 +1345,7 @@ movsb %es:(%esi), %es:(%edi)
movsl %es:(%esi), %es:(%edi)

// CHECK: movsw %es:(%esi), %es:(%edi)
// CHECK: encoding: [0x66,0x26,0xa5]
// CHECK: encoding: [0x26,0x66,0xa5]
movsw %es:(%esi), %es:(%edi)

// CHECK: movw $0, -485498096(%edx,%eax,4)
Expand Down Expand Up @@ -2221,15 +2221,15 @@ rep cmpsb %es:(%edi), %es:(%esi)
rep cmpsl %es:(%edi), %es:(%esi)

// CHECK: rep cmpsw %es:(%edi), %es:(%esi)
// CHECK: encoding: [0xf3,0x66,0x26,0xa7]
// CHECK: encoding: [0xf3,0x26,0x66,0xa7]
rep cmpsw %es:(%edi), %es:(%esi)

// CHECK: rep lodsb %es:(%esi), %al
// CHECK: encoding: [0xf3,0x26,0xac]
rep lodsb %es:(%esi), %al

// CHECK: rep lodsw %es:(%esi), %ax
// CHECK: encoding: [0xf3,0x66,0x26,0xad]
// CHECK: encoding: [0xf3,0x26,0x66,0xad]
rep lodsw %es:(%esi), %ax

// CHECK: rep movsb %es:(%esi), %es:(%edi)
Expand All @@ -2241,7 +2241,7 @@ rep movsb %es:(%esi), %es:(%edi)
rep movsl %es:(%esi), %es:(%edi)

// CHECK: rep movsw %es:(%esi), %es:(%edi)
// CHECK: encoding: [0xf3,0x66,0x26,0xa5]
// CHECK: encoding: [0xf3,0x26,0x66,0xa5]
rep movsw %es:(%esi), %es:(%edi)

// CHECK: repne cmpsb %es:(%edi), %es:(%esi)
Expand All @@ -2253,15 +2253,15 @@ repne cmpsb %es:(%edi), %es:(%esi)
repne cmpsl %es:(%edi), %es:(%esi)

// CHECK: repne cmpsw %es:(%edi), %es:(%esi)
// CHECK: encoding: [0xf2,0x66,0x26,0xa7]
// CHECK: encoding: [0xf2,0x26,0x66,0xa7]
repne cmpsw %es:(%edi), %es:(%esi)

// CHECK: repne lodsb %es:(%esi), %al
// CHECK: encoding: [0xf2,0x26,0xac]
repne lodsb %es:(%esi), %al

// CHECK: repne lodsw %es:(%esi), %ax
// CHECK: encoding: [0xf2,0x66,0x26,0xad]
// CHECK: encoding: [0xf2,0x26,0x66,0xad]
repne lodsw %es:(%esi), %ax

// CHECK: repne movsb %es:(%esi), %es:(%edi)
Expand All @@ -2273,7 +2273,7 @@ repne movsb %es:(%esi), %es:(%edi)
repne movsl %es:(%esi), %es:(%edi)

// CHECK: repne movsw %es:(%esi), %es:(%edi)
// CHECK: encoding: [0xf2,0x66,0x26,0xa5]
// CHECK: encoding: [0xf2,0x26,0x66,0xa5]
repne movsw %es:(%esi), %es:(%edi)

// CHECK: repne scasb %es:(%edi), %al
Expand Down
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