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

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-mc

Author: Freddy Ye (FreddyLeaf)

<details>
<summary>Changes</summary>



---
Full diff: https://github.com/llvm/llvm-project/pull/85175.diff


3 Files Affected:

- (modified) llvm/lib/Target/X86/MCTargetDesc/X86AsmBackend.cpp (+2-1) 
- (modified) llvm/lib/Target/X86/MCTargetDesc/X86EncodingOptimizationForImmediate.def (+6) 
- (added) llvm/test/MC/X86/apx/ccmp-reloc.s (+14) 


``````````diff
diff --git a/llvm/lib/Target/X86/MCTargetDesc/X86AsmBackend.cpp b/llvm/lib/Target/X86/MCTargetDesc/X86AsmBackend.cpp
index 99dc9797f6df92..472f34a4efdb47 100644
--- a/llvm/lib/Target/X86/MCTargetDesc/X86AsmBackend.cpp
+++ b/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,
diff --git a/llvm/lib/Target/X86/MCTargetDesc/X86EncodingOptimizationForImmediate.def b/llvm/lib/Target/X86/MCTargetDesc/X86EncodingOptimizationForImmediate.def
index 27b6a654e6eb7f..f3997a092e4591 100644
--- a/llvm/lib/Target/X86/MCTargetDesc/X86EncodingOptimizationForImmediate.def
+++ b/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)
diff --git a/llvm/test/MC/X86/apx/ccmp-reloc.s b/llvm/test/MC/X86/apx/ccmp-reloc.s
new file mode 100644
index 00000000000000..0e194d812a9c19
--- /dev/null
+++ b/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_32
+ccmpbq	{dfv=of}	$foo, 123(%r8,%rax,4)   // CHECK-NEXT:     R_X86_64_32
+// CHECK-NEXT:   }
+// CHECK-NEXT: ]
\ No newline at end of file

``````````

</details>


https://github.com/llvm/llvm-project/pull/85175