[llvm-commits] [llvm] r141274 - in /llvm/trunk: lib/Target/X86/X86InstrInfo.td lib/Target/X86/X86RegisterInfo.td test/MC/X86/x86-32.s test/MC/X86/x86-64.s utils/TableGen/EDEmitter.cpp utils/TableGen/X86RecognizableInstr.cpp

[Török Edwin]

On 10/07/2011 01:24 AM, Eli Friedman wrote:
> On Wed, Oct 5, 2011 at 11:44 PM, Craig Topper <craig.topper at gmail.com> wrote:
>> Author: ctopper
>> Date: Thu Oct  6 01:44:41 2011
>> New Revision: 141274
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=141274&view=rev
>> Log:
>> Fix assembling of xchg %eax, %eax to not use the NOP encoding of 0x90. This was done by creating a new register group that excludes AX registers. Fixes PR10345. Also added aliases for flipping the order of the operands of xchg <reg>, %eax.
>>
>> Modified:
>>    llvm/trunk/lib/Target/X86/X86InstrInfo.td
>>    llvm/trunk/lib/Target/X86/X86RegisterInfo.td
>>    llvm/trunk/test/MC/X86/x86-32.s
>>    llvm/trunk/test/MC/X86/x86-64.s
>>    llvm/trunk/utils/TableGen/EDEmitter.cpp
>>    llvm/trunk/utils/TableGen/X86RecognizableInstr.cpp
>>
>> Modified: llvm/trunk/lib/Target/X86/X86InstrInfo.td
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86InstrInfo.td?rev=141274&r1=141273&r2=141274&view=diff
>> ==============================================================================
>> --- llvm/trunk/lib/Target/X86/X86InstrInfo.td (original)
>> +++ llvm/trunk/lib/Target/X86/X86InstrInfo.td Thu Oct  6 01:44:41 2011
>> @@ -1154,11 +1154,11 @@
>>                   "xchg{q}\t{$val, $src|$src, $val}", []>;
>>  }
>>
>> -def XCHG16ar : I<0x90, AddRegFrm, (outs), (ins GR16:$src),
>> +def XCHG16ar : I<0x90, AddRegFrm, (outs), (ins GR16_NOAX:$src),
>>                   "xchg{w}\t{$src, %ax|AX, $src}", []>, OpSize;
>> -def XCHG32ar : I<0x90, AddRegFrm, (outs), (ins GR32:$src),
>> +def XCHG32ar : I<0x90, AddRegFrm, (outs), (ins GR32_NOAX:$src),
>>                   "xchg{l}\t{$src, %eax|EAX, $src}", []>;
>> -def XCHG64ar : RI<0x90, AddRegFrm, (outs), (ins GR64:$src),
>> +def XCHG64ar : RI<0x90, AddRegFrm, (outs), (ins GR64_NOAX:$src),
>>                   "xchg{q}\t{$src, %rax|RAX, $src}", []>;
>>
>>
>> @@ -1714,3 +1714,8 @@
>>  def : InstAlias<"xchgw $mem, $val", (XCHG16rm GR16:$val, i16mem:$mem)>;
>>  def : InstAlias<"xchgl $mem, $val", (XCHG32rm GR32:$val, i32mem:$mem)>;
>>  def : InstAlias<"xchgq $mem, $val", (XCHG64rm GR64:$val, i64mem:$mem)>;
>> +
>> +// xchg: We accept "xchgX <reg>, %eax" and "xchgX %eax, <reg>" as synonyms.
>> +def : InstAlias<"xchgw %ax, $src", (XCHG16ar GR16_NOAX:$src)>;
>> +def : InstAlias<"xchgl %eax, $src", (XCHG32ar GR32_NOAX:$src)>;
>> +def : InstAlias<"xchgq %rax, $src", (XCHG64ar GR64_NOAX:$src)>;
>>
>> Modified: llvm/trunk/lib/Target/X86/X86RegisterInfo.td
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86RegisterInfo.td?rev=141274&r1=141273&r2=141274&view=diff
>> ==============================================================================
>> --- llvm/trunk/lib/Target/X86/X86RegisterInfo.td (original)
>> +++ llvm/trunk/lib/Target/X86/X86RegisterInfo.td Thu Oct  6 01:44:41 2011
>> @@ -390,6 +390,23 @@
>>                        (GR32_NOREX sub_32bit)];
>>  }
>>
>> +// GR16_NOAX - GR16 registers except AX.
>> +def GR16_NOAX : RegisterClass<"X86", [i16], 16, (sub GR16, AX)> {
>> +  let SubRegClasses = [(GR8 sub_8bit, sub_8bit_hi)];
>> +}
>> +
>> +// GR32_NOAX - GR32 registers except EAX.
>> +def GR32_NOAX : RegisterClass<"X86", [i32], 32, (sub GR32, EAX)> {
>> +  let SubRegClasses = [(GR8 sub_8bit, sub_8bit_hi), (GR16_NOAX sub_16bit)];
>> +}
>> +
>> +// GR64_NOAX - GR64 registers except RAX.
>> +def GR64_NOAX : RegisterClass<"X86", [i64], 64, (sub GR64, RAX)> {
>> +  let SubRegClasses = [(GR8 sub_8bit, sub_8bit_hi),
>> +                       (GR16_NOAX sub_16bit),
>> +                       (GR32_NOAX sub_32bit)];
>> +}
>> +
>>  // GR32_NOSP - GR32 registers except ESP.
>>  def GR32_NOSP : RegisterClass<"X86", [i32], 32, (sub GR32, ESP)> {
>>   let SubRegClasses = [(GR8 sub_8bit, sub_8bit_hi), (GR16 sub_16bit)];
>>
>> Modified: llvm/trunk/test/MC/X86/x86-32.s
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/MC/X86/x86-32.s?rev=141274&r1=141273&r2=141274&view=diff
>> ==============================================================================
>> --- llvm/trunk/test/MC/X86/x86-32.s (original)
>> +++ llvm/trunk/test/MC/X86/x86-32.s Thu Oct  6 01:44:41 2011
>> @@ -946,3 +946,19 @@
>>  // CHECK: encoding: [0xde,0xe2]
>>  fsubp   %st, %st(2)
>>
>> +// PR10345
>> +// CHECK: xchgl %eax, %eax
>> +// CHECK: encoding: [0x87,0xc0]
>> +xchgl %eax, %eax
>> +
>> +// CHECK: xchgw %ax, %ax
>> +// CHECK: encoding: [0x66,0x87,0xc0]
>> +xchgw %ax, %ax
> 
> Is this really correct for x86-32?  On my system, binutils prefers
> 0x90 on x86-32, and 0x87,0xc0 on x86-64.

How is xchg %eax, %eax different from a nop?
They both do nothing...

Best regards,
--Edwin