[X86][MC] Support encoding optimization & assembler relaxation about immediate operands for CCMP (#85175)

Author: FreddyLeaf

llvm/lib/Target/X86/MCTargetDesc/X86AsmBackend.cpp

@@ -723,9 +723,10 @@ void X86AsmBackend::applyFixup(const MCAssembler &Asm, const MCFixup &Fixup,
 bool X86AsmBackend::mayNeedRelaxation(const MCInst &MI,
                                       const MCSubtargetInfo &STI) const {
   unsigned Opcode = MI.getOpcode();
+  unsigned SkipOperands = X86::isCCMPCC(Opcode) ? 2 : 0;
   return isRelaxableBranch(Opcode) ||
          (X86::getOpcodeForLongImmediateForm(Opcode) != Opcode &&
-          MI.getOperand(MI.getNumOperands() - 1).isExpr());
+          MI.getOperand(MI.getNumOperands() - 1 - SkipOperands).isExpr());
 }
 
 bool X86AsmBackend::fixupNeedsRelaxation(const MCFixup &Fixup,

llvm/lib/Target/X86/MCTargetDesc/X86EncodingOptimizationForImmediate.def

@@ -18,6 +18,12 @@ ENTRY(CMP32mi, CMP32mi8)
 ENTRY(CMP32ri, CMP32ri8)
 ENTRY(CMP64mi32, CMP64mi8)
 ENTRY(CMP64ri32, CMP64ri8)
+ENTRY(CCMP16mi, CCMP16mi8)
+ENTRY(CCMP16ri, CCMP16ri8)
+ENTRY(CCMP32mi, CCMP32mi8)
+ENTRY(CCMP32ri, CCMP32ri8)
+ENTRY(CCMP64mi32, CCMP64mi8)
+ENTRY(CCMP64ri32, CCMP64ri8)
 ENTRY(PUSH16i, PUSH16i8)
 ENTRY(PUSH32i, PUSH32i8)
 ENTRY(PUSH64i32, PUSH64i8)

llvm/test/MC/X86/apx/ccmp-reloc.s

@@ -0,0 +1,14 @@
+// RUN: llvm-mc -triple x86_64-linux-gnu -filetype=obj %s | llvm-readobj -r - | FileCheck %s
+
+// CHECK:      Relocations [
+// CHECK-NEXT:   Section ({{[0-9]+}}) .rela.text {
+ccmpbb	{dfv=of}	$foo, %bl               // CHECK-NEXT:     R_X86_64_8
+ccmpbb	{dfv=of}	$foo, 123(%r8,%rax,4)   // CHECK-NEXT:     R_X86_64_8
+ccmpbw	{dfv=of}	$foo, %bx               // CHECK-NEXT:     R_X86_64_16
+ccmpbw	{dfv=of}	$foo, 123(%r8,%rax,4)   // CHECK-NEXT:     R_X86_64_16
+ccmpbl	{dfv=of}	$foo, %ebx              // CHECK-NEXT:     R_X86_64_32
+ccmpbl	{dfv=of}	$foo, 123(%r8,%rax,4)   // CHECK-NEXT:     R_X86_64_32
+ccmpbq	{dfv=of}	$foo, %rbx              // CHECK-NEXT:     R_X86_64_32S
+ccmpbq	{dfv=of}	$foo, 123(%r8,%rax,4)   // CHECK-NEXT:     R_X86_64_32S
+// CHECK-NEXT:   }
+// CHECK-NEXT: ]