MC: X86 intel syntax: Support data32 and data16 better

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

@@ -3563,8 +3563,35 @@ bool X86AsmParser::parseInstruction(ParseInstructionInfo &Info, StringRef Name,
     PatchedName = Name;
 
   // Hacks to handle 'data16' and 'data32'
-  if (PatchedName == "data16" && is16BitMode()) {
-    return Error(NameLoc, "redundant data16 prefix");
+  if (PatchedName == "data16") {
+    if (is16BitMode())
+      return Error(NameLoc, "redundant data16 prefix");
+    if (getLexer().isNot(AsmToken::EndOfStatement)) {
+      StringRef Next = Parser.getTok().getString();
+      getLexer().Lex();
+      // data16 effectively changes the instruction suffix.
+      // TODO Generalize.
+      if (Next == "call")
+        Next = "callw";
+      if (Next == "ljmp")
+        Next = "ljmpw";
+      if (Next == "retf")
+        Next = "retfw";
+      if (Next == "lgdt") {
+        if (is64BitMode()) {
+          // Use the special lgdtq variant with OpSize16 flag.
+          // I think the CPU ignores the prefix anyway--but hey.
+          Next = "lgdtq16";
+        } else {
+          Next = "lgdtw";
+        }
+      }
+
+      Name = Next;
+      PatchedName = Name;
+      ForcedDataPrefix = X86::Is16Bit;
+      IsPrefix = false;
+    }
   }
   if (PatchedName == "data32") {
     if (is32BitMode())
@@ -4585,14 +4612,26 @@ bool X86AsmParser::matchAndEmitIntelInstruction(
     if (X86Op->isImm()) {
       // If it's not a constant fall through and let remainder take care of it.
       const auto *CE = dyn_cast<MCConstantExpr>(X86Op->getImm());
-      unsigned Size = getPointerWidth();
+      // Determine the size. Prioritize the ForcedDataPrefix flag if it was set
+      // by a 'data32' prefix. Otherwise, fall back to the pointer width of the
+      // current mode.
+      unsigned Size = (ForcedDataPrefix == X86::Is32Bit)   ? 32
+                      : (ForcedDataPrefix == X86::Is16Bit) ? 16
+                                                           : getPointerWidth();
+      ForcedDataPrefix = 0;
       if (CE &&
           (isIntN(Size, CE->getValue()) || isUIntN(Size, CE->getValue()))) {
         SmallString<16> Tmp;
         Tmp += Base;
-        Tmp += (is64BitMode())
-                   ? "q"
-                   : (is32BitMode()) ? "l" : (is16BitMode()) ? "w" : " ";
+        // Append the suffix corresponding to the determined size.
+        if (Size == 64)
+          Tmp += "q";
+        else if (Size == 32)
+          Tmp += "l";
+        else if (Size == 16)
+          Tmp += "w";
+        else
+          Tmp += " ";
         Op.setTokenValue(Tmp);
         // Do match in ATT mode to allow explicit suffix usage.
         Match.push_back(MatchInstruction(Operands, Inst, ErrorInfo,

llvm/lib/Target/X86/X86InstrAsmAlias.td

@@ -260,6 +260,9 @@ def : MnemonicAlias<"cqo",  "cqto", "att">;
 // In 64-bit mode lret maps to lretl; it is not ambiguous with lretq.
 def : MnemonicAlias<"lret", "lretw", "att">, Requires<[In16BitMode]>;
 def : MnemonicAlias<"lret", "lretl", "att">, Requires<[Not16BitMode]>;
+def : InstAlias<"lgdtw\t$src", (LGDT16m opaquemem:$src), 0>, Requires<[Not64BitMode]>;
+def : InstAlias<"lgdtq16\t$src", (LGDT64m_16 opaquemem:$src), 0>, Requires<[In64BitMode]>;
+def : InstAlias<"retfw", (LRET16), 0>;
 
 def : MnemonicAlias<"leavel", "leave", "att">, Requires<[Not64BitMode]>;
 def : MnemonicAlias<"leaveq", "leave", "att">, Requires<[In64BitMode]>;
@@ -723,6 +726,7 @@ def : InstAlias<"shrd{l}\t{$reg, $mem|$mem, $reg}", (SHRD32mrCL i32mem:$mem, GR3
 def : InstAlias<"shrd{q}\t{$reg, $mem|$mem, $reg}", (SHRD64mrCL i64mem:$mem, GR64:$reg), 0>;
 
 // test: We accept "testX <reg>, <mem>" and "testX <mem>, <reg>" as synonyms.
+def : InstAlias<"ljmpw\t$seg, $off", (FARJMP16i i16imm:$off, i16imm:$seg)>, Requires<[Not64BitMode]>;
 def : InstAlias<"test{b}\t{$mem, $val|$val, $mem}",
                 (TEST8mr  i8mem :$mem, GR8 :$val), 0>;
 def : InstAlias<"test{w}\t{$mem, $val|$val, $mem}",

llvm/lib/Target/X86/X86InstrSystem.td

@@ -427,6 +427,9 @@ def LGDT32m : I<0x01, MRM2m, (outs), (ins opaquemem:$src),
                 "lgdt{l|d}\t$src", []>, OpSize32, TB, Requires<[Not64BitMode]>;
 def LGDT64m : I<0x01, MRM2m, (outs), (ins opaquemem:$src),
                 "lgdt{q}\t$src", []>, TB, Requires<[In64BitMode]>;
+// Special variant with data16 prefix (OpSize16) for 64-bit mode
+def LGDT64m_16 : I<0x01, MRM2m, (outs), (ins opaquemem:$src),
+                 "lgdt{q}\t$src", []>, TB, OpSize16, Requires<[In64BitMode]>;
 def LIDT16m : I<0x01, MRM3m, (outs), (ins opaquemem:$src),
                 "lidtw\t$src", []>, TB, OpSize16, Requires<[Not64BitMode]>;
 def LIDT32m : I<0x01, MRM3m, (outs), (ins opaquemem:$src),

llvm/test/MC/X86/intel-syntax-32.s

@@ -1,6 +1,35 @@
-// RUN: llvm-mc -triple i686-unknown-unknown -x86-asm-syntax=intel %s | FileCheck %s
+// RUN: llvm-mc -triple i686-unknown-unknown -x86-asm-syntax=intel --show-encoding %s | FileCheck %s
 
 // CHECK: leaw	(%bp,%si), %ax
+// CHECK: encoding: [0x67,0x66,0x8d,0x02]
 lea ax, [bp+si]
 // CHECK: leaw	(%bp,%si), %ax
+// CHECK: encoding: [0x67,0x66,0x8d,0x02]
 lea ax, [si+bp]
+
+// CHECK: encoding: [0x66,0x6a,0x08]
+          data16 push 8
+
+// CHECK: encoding: [0x6a,0x08]
+          push 8
+
+// CHECK: encoding: [0x66,0xcb]
+          data16 retf
+
+// CHECK: encoding: [0xcb]
+          retf
+
+// CHECK: encoding: [0x66,0x9a,0xcd,0xab,0xce,0x7a]
+          data16 call 0x7ace, 0xabcd
+
+// CHECK: encoding: [0x9a,0xcd,0xab,0x00,0x00,0xce,0x7a]
+          call 0x7ace, 0xabcd
+
+// CHECK: encoding: [0xe8,A,A,A,A]
+          call a
+
+// CHECK: encoding: [0x66,0xea,0xcd,0xab,0xce,0x7a]
+          data16 ljmp 0x7ace, 0xabcd
+
+// CHECK: encoding: [0xea,0xcd,0xab,0x00,0x00,0xce,0x7a]
+          ljmp 0x7ace, 0xabcd

llvm/test/MC/X86/x86-16-intel.s

@@ -0,0 +1,13 @@
+// RUN: llvm-mc -triple i386-unknown-unknown-code16 --x86-asm-syntax=intel --show-encoding %s | FileCheck %s
+
+// CHECK: pushl $8
+// CHECK: encoding: [0x66,0x6a,0x08]
+          data32 push 8
+
+// CHECK: pushw $8
+// CHECK: encoding: [0x6a,0x08]
+          push 8
+
+// CHECK: lretl
+// CHECK: encoding: [0x66,0xcb]
+          data32 retf

llvm/test/MC/X86/x86-16.s

@@ -1060,3 +1060,15 @@ xresldtrk
 // CHECK:  encoding: [0x66,0x8b,0x1e,A,A]
 // CHECK:  fixup A - offset: 3, value: nearer, kind: FK_Data_2
 movl    nearer, %ebx
+
+// CHECK: pushl $8
+// CHECK:  encoding: [0x66,0x6a,0x08]
+data32 push $8
+
+// CHECK: pushl $8
+// CHECK:  encoding: [0x66,0x6a,0x08]
+pushl $8
+
+// CHECK: pushw $8
+// CHECK:  encoding: [0x6a,0x08]
+push $8