[PATCH] D134441: [ObjC][ARC] Don't use operand bundle "clang.arc.attachedcall" in codegen for Windows

[Stefan Gränitz via Phabricator via cfe-commits]

sgraenitz updated this revision to Diff 462871.
sgraenitz added a comment.
Herald added a subscriber: hiraditya.
Herald added a project: LLVM.

Follow Reid's advice from https://github.com/llvm/llvm-project/issues/56952#issuecomment-1255552565 
and fix the instruction sequence expanded from CALL_RVMARKER on Windows (use RCX as target 
register and not RDI). This way we stay as close as possible to Apple's ABI and GNUstep has the 
option to implement detection of optimized callers for autorelease optimizations in the future.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D134441/new/

https://reviews.llvm.org/D134441

Files:
  llvm/lib/Target/X86/X86ExpandPseudo.cpp
  llvm/test/CodeGen/X86/call-rv-marker.ll


Index: llvm/test/CodeGen/X86/call-rv-marker.ll
===================================================================
--- llvm/test/CodeGen/X86/call-rv-marker.ll
+++ llvm/test/CodeGen/X86/call-rv-marker.ll
@@ -1,4 +1,5 @@
 ; RUN: llc -mtriple=x86_64-apple-macosx -verify-machineinstrs -o - %s | FileCheck --check-prefix=CHECK %s
+; RUN: llc -mtriple=x86_64-windows-msvc -verify-machineinstrs -o - %s | FileCheck --check-prefix=WINABI %s
 
 ; TODO: support marker generation with GlobalISel
 target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
@@ -33,6 +34,12 @@
 ; CHECK-NEXT:    popq    %rcx
 ; CHECK-NEXT:    retq
 ;
+; WINABI-LABEL: rv_marker_1_retain:
+; WINABI:        callq   foo1
+; WINABI-NEXT:   movq    %rax, %rcx
+; WINABI-NEXT:   callq   objc_retainAutoreleasedReturnValue
+; WINABI-NEXT:   nop
+;
 entry:
   %call = call ptr @foo1() [ "clang.arc.attachedcall"(ptr @objc_retainAutoreleasedReturnValue) ]
   ret ptr %call
Index: llvm/lib/Target/X86/X86ExpandPseudo.cpp
===================================================================
--- llvm/lib/Target/X86/X86ExpandPseudo.cpp
+++ llvm/lib/Target/X86/X86ExpandPseudo.cpp
@@ -224,9 +224,11 @@
   // Emit marker "movq %rax, %rdi".  %rdi is not callee-saved, so it cannot be
   // live across the earlier call. The call to the ObjC runtime function returns
   // the first argument, so the value of %rax is unchanged after the ObjC
-  // runtime call.
+  // runtime call. On Windows targets, the runtime call follows the regular
+  // x64 calling convention and expects the first argument in %rcx.
+  auto TargetReg = STI->getTargetTriple().isOSWindows() ? X86::RCX : X86::RDI;
   auto *Marker = BuildMI(MBB, MBBI, MI.getDebugLoc(), TII->get(X86::MOV64rr))
-                     .addReg(X86::RDI, RegState::Define)
+                     .addReg(TargetReg, RegState::Define)
                      .addReg(X86::RAX)
                      .getInstr();
   if (MI.shouldUpdateCallSiteInfo())


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