[X86][AsmParser] Refactor code in AsmParser

[skan]

Summary

1. Share code optimizeInstFromVEX3ToVEX2 with MCInstLower
2. Move the code of optimization for shift/rotate to a separate file

[barannikov88]

llvm/lib/Target/X86/AsmParser/X86AsmParser.cpp

3814

The comment was kind of useful. I was about to suggest adding InstAlias.

[barannikov88]

llvm/lib/Target/X86/X86InstrAsmAlias.td

554

I think this can be done by implementing validateTargetOperandClass for MCK__36_1 ($1).
See how ARM does this.

[craig.topper]

llvm/lib/Target/X86/MCTargetDesc/X86InstrOptimization.cpp

1 ↗

(On Diff #520188)

X86EncodingOptimixation might be a better name?

70 ↗

(On Diff #520188)

I think you could have a single argument and add the i or 1 suffix inside the macro.

[craig.topper]

llvm/lib/Target/X86/AsmParser/X86AsmParser.cpp

3814

Agreed. Just say "We can't write this as an InstAlias."

llvm/lib/Target/X86/MCTargetDesc/X86InstrOptimization.cpp

18 ↗

(On Diff #520188)

Adda blank line before this.

19 ↗

(On Diff #520188)

Perhaps you could do something like

unsigned OpIdx1, OpIdx2;
unsigned NewOpc;
switch (Opc)
default:
  return true;
// Use macros to set OpIdx1, OpIdx2, NewOpc;
}

if (X86II::isX86_64ExtendedReg(MI.getOperand(OpIx1).getReg()) ||
    !X86II::isX86_64ExtendedReg(MI.getOperand(OpIdx2).getReg()))
  return false;
MI.setOpcode(New);
return true;

Then you're not duplicating the calls to isX86_64ExtendedReg and setOpcode in every macro?

55 ↗

(On Diff #520188)

Why bring iterators into this? Can't we use getNumOperands() - 1?

62 ↗

(On Diff #520188)

Do this outside the switch instead of duplicating for each case?

[craig.topper]

llvm/lib/Target/X86/MCTargetDesc/X86InstrOptimization.cpp

54 ↗

(On Diff #520188)

Not for this patch, but should we use this in X86MCInstLower and remove all the isel patterns that select the 1 immediate version?

[skan]

Address review comments

[skan]

llvm/lib/Target/X86/MCTargetDesc/X86InstrOptimization.cpp

54 ↗

(On Diff #520188)

Not for this patch, but should we use this in X86MCInstLower and remove all the isel patterns that select the 1 immediate version?

Good idea! I can do it after this patch.

55 ↗

(On Diff #520188)

Why bring iterators into this? Can't we use getNumOperands() - 1?

llvm/lib/Target/X86/X86InstrAsmAlias.td

554

Thanks for the info! I added the comments to optimizeShiftRotateWithImmediateOne.

[craig.topper]

llvm/lib/Target/X86/AsmParser/X86AsmParser.cpp

3661–3662

Can we use Inst.clear()?

llvm/lib/Target/X86/MCTargetDesc/X86EncodingOptimization.cpp

70

Why not make this part of the TO_IMM1 macro?

[barannikov88]

llvm/lib/Target/X86/X86InstrAsmAlias.td

554

I tried to do what I suggested and it doesn't work for all cases.
The "short" variants should be matched first, but this is not always happening.
Currently there doesn't seem to be a way to force ordering between the variants.
(AsmOperandClass has SuperClasses field that guarantees partial ordering, but there is no explicit operand to attach the class to.)

[skan]

Address review comments: Integrate FROM_TO to TO_IMM1

[skan]

llvm/lib/Target/X86/X86InstrAsmAlias.td

554

I tried to do what I suggested and it doesn't work for all cases.
The "short" variants should be matched first, but this is not always happening.
Currently there doesn't seem to be a way to force ordering between the variants.
(AsmOperandClass has SuperClasses field that guarantees partial ordering, but there is no explicit operand to attach the class to.)

It doesn't matter. As craig suggested, we may remove all the isel patterns that select the 1 immediate version by optimizeShiftRotateWithImmediateOne, so InstAlias might be not a better direction.

But I still think the comment about validateTargetOperandClass is valuable b/c it provides a new perspective.

[skan]

Address review comments: Use Inst.clear()

[craig.topper]

LGTM with that comment.

llvm/lib/Target/X86/MCTargetDesc/X86EncodingOptimization.cpp

68

This can be moved below the switch and then you wouldn't need to check how many operands there are.

[skan]

Address review comments: simplify code

[rupprecht]

Is it expected that this patch would cause any differences in the final binary? It seems to be just a refactoring, but we bisected a runtime crash to this commit.

[skan]

In D150068#4336844, @rupprecht wrote:

Is it expected that this patch would cause any differences in the final binary? It seems to be just a refactoring, but we bisected a runtime crash to this commit.

It should not cause any difference in binary in theory. Could you show the difference or provide a small reproducer?

[rupprecht]

In D150068#4336864, @skan wrote:

In D150068#4336844, @rupprecht wrote:

Is it expected that this patch would cause any differences in the final binary? It seems to be just a refactoring, but we bisected a runtime crash to this commit.

It should not cause any difference in binary in theory. Could you show the difference or provide a small reproducer?

I don't have anything yet, since it's an internal test case. I'm going to bisect what the difference is, but it's still reproducing a failure at this commit but not the one prior -- so _something_ must be different, I think.

[alexfh]

With -Os and -march=haswell the patch produces differences similar to this one:

        vpsrldq $8, %xmm8, %xmm8                # xmm8 = xmm8[8,9,10,11,12,13,14,15],zero,zero,zero,zero,zero,zero,zero,zero
        vpxor   %xmm8, %xmm9, %xmm8
        vpsrldq $4, %xmm8, %xmm9                # xmm9 = xmm8[4,5,6,7,8,9,10,11,12,13,14,15],zero,zero,zero,zero
-       vmovss  %xmm8, %xmm4, %xmm8             # xmm8 = xmm8[0],xmm4[1,2,3]
+       vmovss  %xmm4, %xmm8, %xmm8             # xmm8 = xmm4[0],xmm8[1,2,3]
        vpclmulqdq      $0, %xmm8, %xmm5, %xmm8
        vpxor   %xmm9, %xmm8, %xmm8
-       vmovss  %xmm8, %xmm4, %xmm9             # xmm9 = xmm8[0],xmm4[1,2,3]
+       vmovss  %xmm4, %xmm8, %xmm9             # xmm9 = xmm4[0],xmm8[1,2,3]
        vpclmulqdq      $1, %xmm9, %xmm6, %xmm9
-       vmovss  %xmm9, %xmm4, %xmm9             # xmm9 = xmm9[0],xmm4[1,2,3]
+       vmovss  %xmm4, %xmm9, %xmm9             # xmm9 = xmm4[0],xmm9[1,2,3]
        vpclmulqdq      $0, %xmm9, %xmm7, %xmm9
        vpxor   %xmm9, %xmm8, %xmm8
        vpextrd $1, %xmm8, %ecx

Looks wrong to me.

[skan]

In D150068#4337235, @alexfh wrote:

With -Os and -march=haswell the patch produces differences similar to this one:

        vpsrldq $8, %xmm8, %xmm8                # xmm8 = xmm8[8,9,10,11,12,13,14,15],zero,zero,zero,zero,zero,zero,zero,zero
        vpxor   %xmm8, %xmm9, %xmm8
        vpsrldq $4, %xmm8, %xmm9                # xmm9 = xmm8[4,5,6,7,8,9,10,11,12,13,14,15],zero,zero,zero,zero
-       vmovss  %xmm8, %xmm4, %xmm8             # xmm8 = xmm8[0],xmm4[1,2,3]
+       vmovss  %xmm4, %xmm8, %xmm8             # xmm8 = xmm4[0],xmm8[1,2,3]
        vpclmulqdq      $0, %xmm8, %xmm5, %xmm8
        vpxor   %xmm9, %xmm8, %xmm8
-       vmovss  %xmm8, %xmm4, %xmm9             # xmm9 = xmm8[0],xmm4[1,2,3]
+       vmovss  %xmm4, %xmm8, %xmm9             # xmm9 = xmm4[0],xmm8[1,2,3]
        vpclmulqdq      $1, %xmm9, %xmm6, %xmm9
-       vmovss  %xmm9, %xmm4, %xmm9             # xmm9 = xmm9[0],xmm4[1,2,3]
+       vmovss  %xmm4, %xmm9, %xmm9             # xmm9 = xmm4[0],xmm9[1,2,3]
        vpclmulqdq      $0, %xmm9, %xmm7, %xmm9
        vpxor   %xmm9, %xmm8, %xmm8
        vpextrd $1, %xmm8, %ecx

Looks wrong to me.

I think I know what's the bug here and will prepare a patch to fix it soon.

[alexfh]

In D150068#4337333, @skan wrote:

In D150068#4337235, @alexfh wrote:

With -Os and -march=haswell the patch produces differences similar to this one:

        vpsrldq $8, %xmm8, %xmm8                # xmm8 = xmm8[8,9,10,11,12,13,14,15],zero,zero,zero,zero,zero,zero,zero,zero
        vpxor   %xmm8, %xmm9, %xmm8
        vpsrldq $4, %xmm8, %xmm9                # xmm9 = xmm8[4,5,6,7,8,9,10,11,12,13,14,15],zero,zero,zero,zero
-       vmovss  %xmm8, %xmm4, %xmm8             # xmm8 = xmm8[0],xmm4[1,2,3]
+       vmovss  %xmm4, %xmm8, %xmm8             # xmm8 = xmm4[0],xmm8[1,2,3]
        vpclmulqdq      $0, %xmm8, %xmm5, %xmm8
        vpxor   %xmm9, %xmm8, %xmm8
-       vmovss  %xmm8, %xmm4, %xmm9             # xmm9 = xmm8[0],xmm4[1,2,3]
+       vmovss  %xmm4, %xmm8, %xmm9             # xmm9 = xmm4[0],xmm8[1,2,3]
        vpclmulqdq      $1, %xmm9, %xmm6, %xmm9
-       vmovss  %xmm9, %xmm4, %xmm9             # xmm9 = xmm9[0],xmm4[1,2,3]
+       vmovss  %xmm4, %xmm9, %xmm9             # xmm9 = xmm4[0],xmm9[1,2,3]
        vpclmulqdq      $0, %xmm9, %xmm7, %xmm9
        vpxor   %xmm9, %xmm8, %xmm8
        vpextrd $1, %xmm8, %ecx

Looks wrong to me.

I think I know what's the bug here and will prepare a patch to fix it soon.

The proposed fix (https://reviews.llvm.org/D150440) is a non-trivial change on its own, which might introduce more issues. I suggest to revert this commit to return the trunk to a good state and then get this patch reviewed together with the fix.

llvm/lib/Target/X86/AsmParser/X86AsmParser.cpp

 //===-- X86AsmParser.cpp - Parse X86 assembly to MCInst instructions ------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #include "MCTargetDesc/X86BaseInfo.h"
+#include "MCTargetDesc/X86EncodingOptimization.h"
 #include "MCTargetDesc/X86IntelInstPrinter.h"
 #include "MCTargetDesc/X86MCExpr.h"
 #include "MCTargetDesc/X86MCTargetDesc.h"
 #include "MCTargetDesc/X86TargetStreamer.h"
 #include "TargetInfo/X86TargetInfo.h"
 #include "X86AsmParserCommon.h"
 #include "X86Operand.h"
 #include "llvm/ADT/STLExtras.h"
bool X86AsmParser::ParseInstruction(ParseInstructionInfo &Info, StringRef Name,
   }
 
   if (Flags)
     Operands.push_back(X86Operand::CreatePrefix(Flags, NameLoc, NameLoc));
   return false;
 }
 
 bool X86AsmParser::processInstruction(MCInst &Inst, const OperandVector &Ops) {
-  const MCRegisterInfo *MRI = getContext().getRegisterInfo();
+  if (ForcedVEXEncoding != VEXEncoding_VEX3 &&
+      X86::optimizeInstFromVEX3ToVEX2(Inst))
+    return true;
+
+  if (X86::optimizeShiftRotateWithImmediateOne(Inst))
+    return true;
 
   switch (Inst.getOpcode()) {
   default: return false;
   case X86::JMP_1:
     // {disp32} forces a larger displacement as if the instruction was relaxed.
     // NOTE: 16-bit mode uses 16-bit displacement even though it says {disp32}.
     // This matches GNU assembler.
     if (ForcedDispEncoding == DispEncoding_Disp32) {
       Inst.setOpcode(is16BitMode() ? X86::JMP_2 : X86::JMP_4);
       return true;
     }
 
     return false;
   case X86::JCC_1:
     // {disp32} forces a larger displacement as if the instruction was relaxed.
     // NOTE: 16-bit mode uses 16-bit displacement even though it says {disp32}.
     // This matches GNU assembler.
     if (ForcedDispEncoding == DispEncoding_Disp32) {
       Inst.setOpcode(is16BitMode() ? X86::JCC_2 : X86::JCC_4);
       return true;
     }
 
     return false;
-  case X86::VMOVZPQILo2PQIrr:
-  case X86::VMOVAPDrr:
-  case X86::VMOVAPDYrr:
-  case X86::VMOVAPSrr:
-  case X86::VMOVAPSYrr:
-  case X86::VMOVDQArr:
-  case X86::VMOVDQAYrr:
-  case X86::VMOVDQUrr:
-  case X86::VMOVDQUYrr:
-  case X86::VMOVUPDrr:
-  case X86::VMOVUPDYrr:
-  case X86::VMOVUPSrr:
-  case X86::VMOVUPSYrr: {
-    // We can get a smaller encoding by using VEX.R instead of VEX.B if one of
-    // the registers is extended, but other isn't.
-    if (ForcedVEXEncoding == VEXEncoding_VEX3 ||
-        MRI->getEncodingValue(Inst.getOperand(0).getReg()) >= 8 ||
-        MRI->getEncodingValue(Inst.getOperand(1).getReg()) < 8)
-      return false;
-
-    unsigned NewOpc;
-    switch (Inst.getOpcode()) {
-    default: llvm_unreachable("Invalid opcode");
-    case X86::VMOVZPQILo2PQIrr: NewOpc = X86::VMOVPQI2QIrr;   break;
-    case X86::VMOVAPDrr:        NewOpc = X86::VMOVAPDrr_REV;  break;
-    case X86::VMOVAPDYrr:       NewOpc = X86::VMOVAPDYrr_REV; break;
-    case X86::VMOVAPSrr:        NewOpc = X86::VMOVAPSrr_REV;  break;
-    case X86::VMOVAPSYrr:       NewOpc = X86::VMOVAPSYrr_REV; break;
-    case X86::VMOVDQArr:        NewOpc = X86::VMOVDQArr_REV;  break;
-    case X86::VMOVDQAYrr:       NewOpc = X86::VMOVDQAYrr_REV; break;
-    case X86::VMOVDQUrr:        NewOpc = X86::VMOVDQUrr_REV;  break;
-    case X86::VMOVDQUYrr:       NewOpc = X86::VMOVDQUYrr_REV; break;
-    case X86::VMOVUPDrr:        NewOpc = X86::VMOVUPDrr_REV;  break;
-    case X86::VMOVUPDYrr:       NewOpc = X86::VMOVUPDYrr_REV; break;
-    case X86::VMOVUPSrr:        NewOpc = X86::VMOVUPSrr_REV;  break;
-    case X86::VMOVUPSYrr:       NewOpc = X86::VMOVUPSYrr_REV; break;
-    }
-    Inst.setOpcode(NewOpc);
-    return true;
-  }
-  case X86::VMOVSDrr:
-  case X86::VMOVSSrr: {
-    // We can get a smaller encoding by using VEX.R instead of VEX.B if one of
-    // the registers is extended, but other isn't.
-    if (ForcedVEXEncoding == VEXEncoding_VEX3 ||
-        MRI->getEncodingValue(Inst.getOperand(0).getReg()) >= 8 ||
-        MRI->getEncodingValue(Inst.getOperand(2).getReg()) < 8)
-      return false;
-
-    unsigned NewOpc;
-    switch (Inst.getOpcode()) {
-    default: llvm_unreachable("Invalid opcode");
-    case X86::VMOVSDrr: NewOpc = X86::VMOVSDrr_REV; break;
-    case X86::VMOVSSrr: NewOpc = X86::VMOVSSrr_REV; break;
-    }
-    Inst.setOpcode(NewOpc);
-    return true;
-  }
-  case X86::RCR8ri: case X86::RCR16ri: case X86::RCR32ri: case X86::RCR64ri:
-  case X86::RCL8ri: case X86::RCL16ri: case X86::RCL32ri: case X86::RCL64ri:
-  case X86::ROR8ri: case X86::ROR16ri: case X86::ROR32ri: case X86::ROR64ri:
-  case X86::ROL8ri: case X86::ROL16ri: case X86::ROL32ri: case X86::ROL64ri:
-  case X86::SAR8ri: case X86::SAR16ri: case X86::SAR32ri: case X86::SAR64ri:
-  case X86::SHR8ri: case X86::SHR16ri: case X86::SHR32ri: case X86::SHR64ri:
-  case X86::SHL8ri: case X86::SHL16ri: case X86::SHL32ri: case X86::SHL64ri: {
-    // Optimize s{hr,ar,hl} $1, <op> to "shift <op>". Similar for rotate.
-    // FIXME: It would be great if we could just do this with an InstAlias.
-    if (!Inst.getOperand(2).isImm() || Inst.getOperand(2).getImm() != 1)
-      return false;
-
-    unsigned NewOpc;
-    switch (Inst.getOpcode()) {
-    default: llvm_unreachable("Invalid opcode");
-    case X86::RCR8ri:  NewOpc = X86::RCR8r1;  break;
-    case X86::RCR16ri: NewOpc = X86::RCR16r1; break;
-    case X86::RCR32ri: NewOpc = X86::RCR32r1; break;
-    case X86::RCR64ri: NewOpc = X86::RCR64r1; break;
-    case X86::RCL8ri:  NewOpc = X86::RCL8r1;  break;
-    case X86::RCL16ri: NewOpc = X86::RCL16r1; break;
-    case X86::RCL32ri: NewOpc = X86::RCL32r1; break;
-    case X86::RCL64ri: NewOpc = X86::RCL64r1; break;
-    case X86::ROR8ri:  NewOpc = X86::ROR8r1;  break;
-    case X86::ROR16ri: NewOpc = X86::ROR16r1; break;
-    case X86::ROR32ri: NewOpc = X86::ROR32r1; break;
-    case X86::ROR64ri: NewOpc = X86::ROR64r1; break;
-    case X86::ROL8ri:  NewOpc = X86::ROL8r1;  break;
-    case X86::ROL16ri: NewOpc = X86::ROL16r1; break;
-    case X86::ROL32ri: NewOpc = X86::ROL32r1; break;
-    case X86::ROL64ri: NewOpc = X86::ROL64r1; break;
-    case X86::SAR8ri:  NewOpc = X86::SAR8r1;  break;
-    case X86::SAR16ri: NewOpc = X86::SAR16r1; break;
-    case X86::SAR32ri: NewOpc = X86::SAR32r1; break;
-    case X86::SAR64ri: NewOpc = X86::SAR64r1; break;
-    case X86::SHR8ri:  NewOpc = X86::SHR8r1;  break;
-    case X86::SHR16ri: NewOpc = X86::SHR16r1; break;
-    case X86::SHR32ri: NewOpc = X86::SHR32r1; break;
-    case X86::SHR64ri: NewOpc = X86::SHR64r1; break;
-    case X86::SHL8ri:  NewOpc = X86::SHL8r1;  break;
-    case X86::SHL16ri: NewOpc = X86::SHL16r1; break;
-    case X86::SHL32ri: NewOpc = X86::SHL32r1; break;
-    case X86::SHL64ri: NewOpc = X86::SHL64r1; break;
-    }
-
-    MCInst TmpInst;
-    TmpInst.setOpcode(NewOpc);
-    TmpInst.addOperand(Inst.getOperand(0));
-    TmpInst.addOperand(Inst.getOperand(1));
-    Inst = TmpInst;
-    return true;
-  }
-  case X86::RCR8mi: case X86::RCR16mi: case X86::RCR32mi: case X86::RCR64mi:
-  case X86::RCL8mi: case X86::RCL16mi: case X86::RCL32mi: case X86::RCL64mi:
-  case X86::ROR8mi: case X86::ROR16mi: case X86::ROR32mi: case X86::ROR64mi:
-  case X86::ROL8mi: case X86::ROL16mi: case X86::ROL32mi: case X86::ROL64mi:
-  case X86::SAR8mi: case X86::SAR16mi: case X86::SAR32mi: case X86::SAR64mi:
-  case X86::SHR8mi: case X86::SHR16mi: case X86::SHR32mi: case X86::SHR64mi:
-  case X86::SHL8mi: case X86::SHL16mi: case X86::SHL32mi: case X86::SHL64mi: {
-    // Optimize s{hr,ar,hl} $1, <op> to "shift <op>". Similar for rotate.
-    // FIXME: It would be great if we could just do this with an InstAlias.
-    if (!Inst.getOperand(X86::AddrNumOperands).isImm() ||
-        Inst.getOperand(X86::AddrNumOperands).getImm() != 1)
-      return false;
-
-    unsigned NewOpc;
-    switch (Inst.getOpcode()) {
-    default: llvm_unreachable("Invalid opcode");
-    case X86::RCR8mi:  NewOpc = X86::RCR8m1;  break;
-    case X86::RCR16mi: NewOpc = X86::RCR16m1; break;
-    case X86::RCR32mi: NewOpc = X86::RCR32m1; break;
-    case X86::RCR64mi: NewOpc = X86::RCR64m1; break;
-    case X86::RCL8mi:  NewOpc = X86::RCL8m1;  break;
-    case X86::RCL16mi: NewOpc = X86::RCL16m1; break;
-    case X86::RCL32mi: NewOpc = X86::RCL32m1; break;
-    case X86::RCL64mi: NewOpc = X86::RCL64m1; break;
-    case X86::ROR8mi:  NewOpc = X86::ROR8m1;  break;
-    case X86::ROR16mi: NewOpc = X86::ROR16m1; break;
-    case X86::ROR32mi: NewOpc = X86::ROR32m1; break;
-    case X86::ROR64mi: NewOpc = X86::ROR64m1; break;
-    case X86::ROL8mi:  NewOpc = X86::ROL8m1;  break;
-    case X86::ROL16mi: NewOpc = X86::ROL16m1; break;
-    case X86::ROL32mi: NewOpc = X86::ROL32m1; break;
-    case X86::ROL64mi: NewOpc = X86::ROL64m1; break;
-    case X86::SAR8mi:  NewOpc = X86::SAR8m1;  break;
-    case X86::SAR16mi: NewOpc = X86::SAR16m1; break;
-    case X86::SAR32mi: NewOpc = X86::SAR32m1; break;
-    case X86::SAR64mi: NewOpc = X86::SAR64m1; break;
-    case X86::SHR8mi:  NewOpc = X86::SHR8m1;  break;
-    case X86::SHR16mi: NewOpc = X86::SHR16m1; break;
-    case X86::SHR32mi: NewOpc = X86::SHR32m1; break;
-    case X86::SHR64mi: NewOpc = X86::SHR64m1; break;
-    case X86::SHL8mi:  NewOpc = X86::SHL8m1;  break;
-    case X86::SHL16mi: NewOpc = X86::SHL16m1; break;
-    case X86::SHL32mi: NewOpc = X86::SHL32m1; break;
-    case X86::SHL64mi: NewOpc = X86::SHL64m1; break;
-    }
-
-    MCInst TmpInst;
-    TmpInst.setOpcode(NewOpc);
-    for (int i = 0; i != X86::AddrNumOperands; ++i)
-      TmpInst.addOperand(Inst.getOperand(i));
-    Inst = TmpInst;
-    return true;
-  }
   case X86::INT: {
-    // Transforms "int $3" into "int3" as a size optimization.  We can't write an
-    // instalias with an immediate operand yet.
+    // Transforms "int $3" into "int3" as a size optimization.
+    // We can't write this as an InstAlias.
     if (!Inst.getOperand(0).isImm() || Inst.getOperand(0).getImm() != 3)
       return false;
-
-    MCInst TmpInst;
-    TmpInst.setOpcode(X86::INT3);
-    Inst = TmpInst;
+    Inst.clear();
+    Inst.setOpcode(X86::INT3);
     return true;
   }
   }
 }
 
 bool X86AsmParser::validateInstruction(MCInst &Inst, const OperandVector &Ops) {
   using namespace X86;
   const MCRegisterInfo *MRI = getContext().getRegisterInfo();

llvm/lib/Target/X86/MCTargetDesc/CMakeLists.txt

 add_llvm_component_library(LLVMX86Desc
   X86ATTInstPrinter.cpp
   X86IntelInstPrinter.cpp
   X86InstComments.cpp
   X86InstPrinterCommon.cpp
   X86InstrRelaxTables.cpp
+  X86EncodingOptimization.cpp
   X86ShuffleDecode.cpp
   X86AsmBackend.cpp
   X86MCTargetDesc.cpp
   X86MCAsmInfo.cpp
   X86MCCodeEmitter.cpp
   X86MachObjectWriter.cpp
   X86MnemonicTables.cpp
   X86ELFObjectWriter.cpp

llvm/lib/Target/X86/MCTargetDesc/X86EncodingOptimization.h

+//===-- X86EncodingOptimization.h - X86 Encoding optimization ---*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains the declarations of the X86 encoding optimization
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIB_TARGET_X86_X86ENCODINGOPTIMIZATION_H
+#define LLVM_LIB_TARGET_X86_X86ENCODINGOPTIMIZATION_H
+namespace llvm {
+class MCInst;
+namespace X86 {
+bool optimizeInstFromVEX3ToVEX2(MCInst &MI);
+bool optimizeShiftRotateWithImmediateOne(MCInst &MI);
+} // namespace X86
+} // namespace llvm
+#endif

llvm/lib/Target/X86/MCTargetDesc/X86EncodingOptimization.cpp

+//===-- X86EncodingOptimization.cpp - X86 Encoding optimization -*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains the implementation of the X86 encoding optimization
+//
+//===----------------------------------------------------------------------===//
+
+#include "X86EncodingOptimization.h"
+#include "X86BaseInfo.h"
+#include "llvm/MC/MCInst.h"
+
+using namespace llvm;
+
+bool X86::optimizeInstFromVEX3ToVEX2(MCInst &MI) {
+  unsigned OpIdx1, OpIdx2;
+  unsigned NewOpc;
+#define FROM_TO(FROM, TO, IDX1, IDX2)                                          \
+  case X86::FROM:                                                              \
+    NewOpc = X86::TO;                                                          \
+    OpIdx1 = IDX1;                                                             \
+    OpIdx2 = IDX2;                                                             \
+    break;
+#define TO_REV(FROM) FROM_TO(FROM, FROM##_REV, 0, 1)
+  switch (MI.getOpcode()) {
+  default:
+    return false;
+    // Commute operands to get a smaller encoding by using VEX.R instead of
+    // VEX.B if one of the registers is extended, but other isn't.
+    FROM_TO(VMOVZPQILo2PQIrr, VMOVPQI2QIrr, 0, 1)
+    TO_REV(VMOVAPDrr)
+    TO_REV(VMOVAPDYrr)
+    TO_REV(VMOVAPSrr)
+    TO_REV(VMOVAPSYrr)
+    TO_REV(VMOVDQArr)
+    TO_REV(VMOVDQAYrr)
+    TO_REV(VMOVDQUrr)
+    TO_REV(VMOVDQUYrr)
+    TO_REV(VMOVUPDrr)
+    TO_REV(VMOVUPDYrr)
+    TO_REV(VMOVUPSrr)
+    TO_REV(VMOVUPSYrr)
+#undef TO_REV
+#define TO_REV(FROM) FROM_TO(FROM, FROM##_REV, 0, 2)
+    TO_REV(VMOVSDrr)
+    TO_REV(VMOVSSrr)
+#undef TO_REV
+#undef FROM_TO
+  }
+  if (X86II::isX86_64ExtendedReg(MI.getOperand(OpIdx1).getReg()) ||
+      !X86II::isX86_64ExtendedReg(MI.getOperand(OpIdx2).getReg()))
+    return false;
+  MI.setOpcode(NewOpc);
+  return true;
+}
+
+// NOTE: We may write this as an InstAlias if it's only used by AsmParser. See
+// validateTargetOperandClass.
+bool X86::optimizeShiftRotateWithImmediateOne(MCInst &MI) {
+  unsigned NewOpc;
+#define TO_IMM1(FROM)                                                          \
+  case X86::FROM##i:                                                           \
+    NewOpc = X86::FROM##1;                                                     \
+    break;
+  switch (MI.getOpcode()) {
+  default:
+    return false;
+    TO_IMM1(RCR8r)
+    TO_IMM1(RCR16r)
+    TO_IMM1(RCR32r)
+    TO_IMM1(RCR64r)
+    TO_IMM1(RCL8r)
+    TO_IMM1(RCL16r)
+    TO_IMM1(RCL32r)
+    TO_IMM1(RCL64r)
+    TO_IMM1(ROR8r)
+    TO_IMM1(ROR16r)
+    TO_IMM1(ROR32r)
+    TO_IMM1(ROR64r)
+    TO_IMM1(ROL8r)
+    TO_IMM1(ROL16r)
+    TO_IMM1(ROL32r)
+    TO_IMM1(ROL64r)
+    TO_IMM1(SAR8r)
+    TO_IMM1(SAR16r)
+    TO_IMM1(SAR32r)
+    TO_IMM1(SAR64r)
+    TO_IMM1(SHR8r)
+    TO_IMM1(SHR16r)
+    TO_IMM1(SHR32r)
+    TO_IMM1(SHR64r)
+    TO_IMM1(SHL8r)
+    TO_IMM1(SHL16r)
+    TO_IMM1(SHL32r)
+    TO_IMM1(SHL64r)
+    TO_IMM1(RCR8m)
+    TO_IMM1(RCR16m)
+    TO_IMM1(RCR32m)
+    TO_IMM1(RCR64m)
+    TO_IMM1(RCL8m)
+    TO_IMM1(RCL16m)
+    TO_IMM1(RCL32m)
+    TO_IMM1(RCL64m)
+    TO_IMM1(ROR8m)
+    TO_IMM1(ROR16m)
+    TO_IMM1(ROR32m)
+    TO_IMM1(ROR64m)
+    TO_IMM1(ROL8m)
+    TO_IMM1(ROL16m)
+    TO_IMM1(ROL32m)
+    TO_IMM1(ROL64m)
+    TO_IMM1(SAR8m)
+    TO_IMM1(SAR16m)
+    TO_IMM1(SAR32m)
+    TO_IMM1(SAR64m)
+    TO_IMM1(SHR8m)
+    TO_IMM1(SHR16m)
+    TO_IMM1(SHR32m)
+    TO_IMM1(SHR64m)
+    TO_IMM1(SHL8m)
+    TO_IMM1(SHL16m)
+    TO_IMM1(SHL32m)
+    TO_IMM1(SHL64m)
+  }
+  MCOperand &LastOp = MI.getOperand(MI.getNumOperands() - 1);
+  if (!LastOp.isImm() || LastOp.getImm() != 1)
+    return false;
+  MI.setOpcode(NewOpc);
+  MI.erase(&LastOp);
+  return true;
+}

llvm/lib/Target/X86/X86InstrAsmAlias.td

 
 def : InstAlias<"shld{w}\t{$reg, $mem|$mem, $reg}", (SHLD16mrCL i16mem:$mem, GR16:$reg), 0>;
 def : InstAlias<"shld{l}\t{$reg, $mem|$mem, $reg}", (SHLD32mrCL i32mem:$mem, GR32:$reg), 0>;
 def : InstAlias<"shld{q}\t{$reg, $mem|$mem, $reg}", (SHLD64mrCL i64mem:$mem, GR64:$reg), 0>;
 def : InstAlias<"shrd{w}\t{$reg, $mem|$mem, $reg}", (SHRD16mrCL i16mem:$mem, GR16:$reg), 0>;
 def : InstAlias<"shrd{l}\t{$reg, $mem|$mem, $reg}", (SHRD32mrCL i32mem:$mem, GR32:$reg), 0>;
 def : InstAlias<"shrd{q}\t{$reg, $mem|$mem, $reg}", (SHRD64mrCL i64mem:$mem, GR64:$reg), 0>;
 
-/*  FIXME: This is disabled because the asm matcher is currently incapable of
- *  matching a fixed immediate like $1.
-// "shl X, $1" is an alias for "shl X".
-multiclass ShiftRotateByOneAlias<string Mnemonic, string Opc> {
- def : InstAlias<!strconcat(Mnemonic, "b $op, $$1"),
-                 (!cast<Instruction>(!strconcat(Opc, "8r1")) GR8:$op)>;
- def : InstAlias<!strconcat(Mnemonic, "w $op, $$1"),
-                 (!cast<Instruction>(!strconcat(Opc, "16r1")) GR16:$op)>;
- def : InstAlias<!strconcat(Mnemonic, "l $op, $$1"),
-                 (!cast<Instruction>(!strconcat(Opc, "32r1")) GR32:$op)>;
- def : InstAlias<!strconcat(Mnemonic, "q $op, $$1"),
-                 (!cast<Instruction>(!strconcat(Opc, "64r1")) GR64:$op)>;
- def : InstAlias<!strconcat(Mnemonic, "b $op, $$1"),
-                 (!cast<Instruction>(!strconcat(Opc, "8m1")) i8mem:$op)>;
- def : InstAlias<!strconcat(Mnemonic, "w $op, $$1"),
-                 (!cast<Instruction>(!strconcat(Opc, "16m1")) i16mem:$op)>;
- def : InstAlias<!strconcat(Mnemonic, "l $op, $$1"),
-                 (!cast<Instruction>(!strconcat(Opc, "32m1")) i32mem:$op)>;
- def : InstAlias<!strconcat(Mnemonic, "q $op, $$1"),
-                 (!cast<Instruction>(!strconcat(Opc, "64m1")) i64mem:$op)>;
-}
-
-defm : ShiftRotateByOneAlias<"rcl", "RCL">;
-defm : ShiftRotateByOneAlias<"rcr", "RCR">;
-defm : ShiftRotateByOneAlias<"rol", "ROL">;
-defm : ShiftRotateByOneAlias<"ror", "ROR">;
-FIXME */
-
 // test: We accept "testX <reg>, <mem>" and "testX <mem>, <reg>" as synonyms.
 def : InstAlias<"test{b}\t{$mem, $val|$val, $mem}",
                 (TEST8mr  i8mem :$mem, GR8 :$val), 0>;
 def : InstAlias<"test{w}\t{$mem, $val|$val, $mem}",
                 (TEST16mr i16mem:$mem, GR16:$val), 0>;
 def : InstAlias<"test{l}\t{$mem, $val|$val, $mem}",
                 (TEST32mr i32mem:$mem, GR32:$val), 0>;
 def : InstAlias<"test{q}\t{$mem, $val|$val, $mem}",

llvm/lib/Target/X86/X86MCInstLower.cpp

 //===-- X86MCInstLower.cpp - Convert X86 MachineInstr to an MCInst --------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // This file contains code to lower X86 MachineInstrs to their corresponding
 // MCInst records.
 //
 //===----------------------------------------------------------------------===//
 
 #include "MCTargetDesc/X86ATTInstPrinter.h"
 #include "MCTargetDesc/X86BaseInfo.h"
+#include "MCTargetDesc/X86EncodingOptimization.h"
 #include "MCTargetDesc/X86InstComments.h"
 #include "MCTargetDesc/X86ShuffleDecode.h"
 #include "MCTargetDesc/X86TargetStreamer.h"
 #include "X86AsmPrinter.h"
 #include "X86RegisterInfo.h"
 #include "X86ShuffleDecodeConstantPool.h"
 #include "X86Subtarget.h"
 #include "llvm/ADT/SmallString.h"

 
 void X86MCInstLower::Lower(const MachineInstr *MI, MCInst &OutMI) const {
   OutMI.setOpcode(MI->getOpcode());
 
   for (const MachineOperand &MO : MI->operands())
     if (auto MaybeMCOp = LowerMachineOperand(MI, MO))
       OutMI.addOperand(*MaybeMCOp);
 
+  if (X86::optimizeInstFromVEX3ToVEX2(OutMI))
+    return;
+
   // Handle a few special cases to eliminate operand modifiers.
   switch (OutMI.getOpcode()) {
   case X86::LEA64_32r:
   case X86::LEA64r:
   case X86::LEA16r:
   case X86::LEA32r:
     // LEA should have a segment register, but it must be empty.
     assert(OutMI.getNumOperands() == 1 + X86::AddrNumOperands &&
case X86::MULX64Hrm: {
     }
     OutMI.setOpcode(NewOpc);
     // Duplicate the destination.
     unsigned DestReg = OutMI.getOperand(0).getReg();
     OutMI.insert(OutMI.begin(), MCOperand::createReg(DestReg));
     break;
   }
 
-  // Commute operands to get a smaller encoding by using VEX.R instead of VEX.B
-  // if one of the registers is extended, but other isn't.
-  case X86::VMOVZPQILo2PQIrr:
-  case X86::VMOVAPDrr:
-  case X86::VMOVAPDYrr:
-  case X86::VMOVAPSrr:
-  case X86::VMOVAPSYrr:
-  case X86::VMOVDQArr:
-  case X86::VMOVDQAYrr:
-  case X86::VMOVDQUrr:
-  case X86::VMOVDQUYrr:
-  case X86::VMOVUPDrr:
-  case X86::VMOVUPDYrr:
-  case X86::VMOVUPSrr:
-  case X86::VMOVUPSYrr: {
-    if (!X86II::isX86_64ExtendedReg(OutMI.getOperand(0).getReg()) &&
-        X86II::isX86_64ExtendedReg(OutMI.getOperand(1).getReg())) {
-      unsigned NewOpc;
-      switch (OutMI.getOpcode()) {
-      default: llvm_unreachable("Invalid opcode");
-      case X86::VMOVZPQILo2PQIrr: NewOpc = X86::VMOVPQI2QIrr;   break;
-      case X86::VMOVAPDrr:        NewOpc = X86::VMOVAPDrr_REV;  break;
-      case X86::VMOVAPDYrr:       NewOpc = X86::VMOVAPDYrr_REV; break;
-      case X86::VMOVAPSrr:        NewOpc = X86::VMOVAPSrr_REV;  break;
-      case X86::VMOVAPSYrr:       NewOpc = X86::VMOVAPSYrr_REV; break;
-      case X86::VMOVDQArr:        NewOpc = X86::VMOVDQArr_REV;  break;
-      case X86::VMOVDQAYrr:       NewOpc = X86::VMOVDQAYrr_REV; break;
-      case X86::VMOVDQUrr:        NewOpc = X86::VMOVDQUrr_REV;  break;
-      case X86::VMOVDQUYrr:       NewOpc = X86::VMOVDQUYrr_REV; break;
-      case X86::VMOVUPDrr:        NewOpc = X86::VMOVUPDrr_REV;  break;
-      case X86::VMOVUPDYrr:       NewOpc = X86::VMOVUPDYrr_REV; break;
-      case X86::VMOVUPSrr:        NewOpc = X86::VMOVUPSrr_REV;  break;
-      case X86::VMOVUPSYrr:       NewOpc = X86::VMOVUPSYrr_REV; break;
-      }
-      OutMI.setOpcode(NewOpc);
-    }
-    break;
-  }
-  case X86::VMOVSDrr:
-  case X86::VMOVSSrr: {
-    if (!X86II::isX86_64ExtendedReg(OutMI.getOperand(0).getReg()) &&
-        X86II::isX86_64ExtendedReg(OutMI.getOperand(2).getReg())) {
-      unsigned NewOpc;
-      switch (OutMI.getOpcode()) {
-      default: llvm_unreachable("Invalid opcode");
-      case X86::VMOVSDrr: NewOpc = X86::VMOVSDrr_REV; break;
-      case X86::VMOVSSrr: NewOpc = X86::VMOVSSrr_REV; break;
-      }
-      OutMI.setOpcode(NewOpc);
-    }
-    break;
-  }
-
   case X86::VPCMPBZ128rmi:  case X86::VPCMPBZ128rmik:
   case X86::VPCMPBZ128rri:  case X86::VPCMPBZ128rrik:
   case X86::VPCMPBZ256rmi:  case X86::VPCMPBZ256rmik:
   case X86::VPCMPBZ256rri:  case X86::VPCMPBZ256rrik:
   case X86::VPCMPBZrmi:     case X86::VPCMPBZrmik:
   case X86::VPCMPBZrri:     case X86::VPCMPBZrrik:
   case X86::VPCMPDZ128rmi:  case X86::VPCMPDZ128rmik:
   case X86::VPCMPDZ128rmib: case X86::VPCMPDZ128rmibk: