[X86] Merge the different Jcc instructions for each condition code into single instructions that store the condition code as an operand.

Summary:
This avoids needing an isel pattern for each condition code. And it removes translation switches for converting between Jcc instructions and condition codes.

Now the printer, encoder and disassembler take care of converting the immediate. We use InstAliases to handle the assembly matching. But we print using the asm string in the instruction definition. The instruction itself is marked IsCodeGenOnly=1 to hide it from the assembly parser.

Reviewers: spatel, lebedev.ri, courbet, gchatelet, RKSimon

Reviewed By: RKSimon

Subscribers: MatzeB, qcolombet, eraman, hiraditya, arphaman, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D60228

llvm-svn: 357802

3 files changed, 17 insertions, 34 deletions

diff --git a/llvm/lib/Target/X86/MCTargetDesc/X86AsmBackend.cpp b/llvm/lib/Target/X86/MCTargetDesc/X86AsmBackend.cpp
index 1e32d002afd..cb6c5c6b207 100644
--- a/llvm/lib/Target/X86/MCTargetDesc/X86AsmBackend.cpp
+++ b/llvm/lib/Target/X86/MCTargetDesc/X86AsmBackend.cpp
@@ -136,40 +136,10 @@ static unsigned getRelaxedOpcodeBranch(const MCInst &Inst, bool is16BitMode) {
   switch (Op) {
   default:
     return Op;
-  case X86::JAE_1:
-    return (is16BitMode) ? X86::JAE_2 : X86::JAE_4;
-  case X86::JA_1:
-    return (is16BitMode) ? X86::JA_2 : X86::JA_4;
-  case X86::JBE_1:
-    return (is16BitMode) ? X86::JBE_2 : X86::JBE_4;
-  case X86::JB_1:
-    return (is16BitMode) ? X86::JB_2 : X86::JB_4;
-  case X86::JE_1:
-    return (is16BitMode) ? X86::JE_2 : X86::JE_4;
-  case X86::JGE_1:
-    return (is16BitMode) ? X86::JGE_2 : X86::JGE_4;
-  case X86::JG_1:
-    return (is16BitMode) ? X86::JG_2 : X86::JG_4;
-  case X86::JLE_1:
-    return (is16BitMode) ? X86::JLE_2 : X86::JLE_4;
-  case X86::JL_1:
-    return (is16BitMode) ? X86::JL_2 : X86::JL_4;
+  case X86::JCC_1:
+    return (is16BitMode) ? X86::JCC_2 : X86::JCC_4;
   case X86::JMP_1:
     return (is16BitMode) ? X86::JMP_2 : X86::JMP_4;
-  case X86::JNE_1:
-    return (is16BitMode) ? X86::JNE_2 : X86::JNE_4;
-  case X86::JNO_1:
-    return (is16BitMode) ? X86::JNO_2 : X86::JNO_4;
-  case X86::JNP_1:
-    return (is16BitMode) ? X86::JNP_2 : X86::JNP_4;
-  case X86::JNS_1:
-    return (is16BitMode) ? X86::JNS_2 : X86::JNS_4;
-  case X86::JO_1:
-    return (is16BitMode) ? X86::JO_2 : X86::JO_4;
-  case X86::JP_1:
-    return (is16BitMode) ? X86::JP_2 : X86::JP_4;
-  case X86::JS_1:
-    return (is16BitMode) ? X86::JS_2 : X86::JS_4;
   }
 }
 
diff --git a/llvm/lib/Target/X86/MCTargetDesc/X86BaseInfo.h b/llvm/lib/Target/X86/MCTargetDesc/X86BaseInfo.h
index 29b6efb922e..1c4eff22d85 100644
--- a/llvm/lib/Target/X86/MCTargetDesc/X86BaseInfo.h
+++ b/llvm/lib/Target/X86/MCTargetDesc/X86BaseInfo.h
@@ -321,6 +321,10 @@ namespace X86II {
     /// manual, this operand is described as pntr16:32 and pntr16:16
     RawFrmImm16 = 8,
 
+    /// AddCCFrm - This form is used for Jcc that encode the condition code
+    /// in the lower 4 bits of the opcode.
+    AddCCFrm = 9,
+
     /// MRM[0-7][rm] - These forms are used to represent instructions that use
     /// a Mod/RM byte, and use the middle field to hold extended opcode
     /// information.  In the intel manual these are represented as /0, /1, ...
@@ -769,6 +773,7 @@ namespace X86II {
     case X86II::RawFrmSrc:
     case X86II::RawFrmDst:
     case X86II::RawFrmDstSrc:
+    case X86II::AddCCFrm:
       return -1;
     case X86II::MRMDestMem:
       return 0;
diff --git a/llvm/lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp b/llvm/lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp
index 05e19a3db1c..d063c4e5a86 100644
--- a/llvm/lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp
+++ b/llvm/lib/Target/X86/MCTargetDesc/X86MCCodeEmitter.cpp
@@ -1273,6 +1273,8 @@ encodeInstruction(const MCInst &MI, raw_ostream &OS,
   if ((TSFlags & X86II::OpMapMask) == X86II::ThreeDNow)
     BaseOpcode = 0x0F;   // Weird 3DNow! encoding.
 
+  unsigned OpcodeOffset = 0;
+
   uint64_t Form = TSFlags & X86II::FormMask;
   switch (Form) {
   default: errs() << "FORM: " << Form << "\n";
@@ -1319,8 +1321,14 @@ encodeInstruction(const MCInst &MI, raw_ostream &OS,
     EmitByte(BaseOpcode, CurByte, OS);
     break;
   }
-  case X86II::RawFrm: {
-    EmitByte(BaseOpcode, CurByte, OS);
+  case X86II::AddCCFrm: {
+    // This will be added to the opcode in the fallthrough.
+    OpcodeOffset = MI.getOperand(NumOps - 1).getImm();
+    assert(OpcodeOffset < 16 && "Unexpected opcode offset!");
+    --NumOps; // Drop the operand from the end.
+    LLVM_FALLTHROUGH;
+  case X86II::RawFrm:
+    EmitByte(BaseOpcode + OpcodeOffset, CurByte, OS);
 
     if (!is64BitMode(STI) || !isPCRel32Branch(MI))
       break;