[CIR][CIRGen] Allow maybeSetTrivialComdat for GlobalOp (#885)

as title, this would complete solution to fix issue [LLVM lowering
missing comdat and constant
attributes](#801)

Author: ghehg

clang/lib/CIR/CodeGen/CIRGenModule.cpp

@@ -1329,7 +1329,7 @@ void CIRGenModule::buildGlobalVarDefinition(const clang::VarDecl *D,
     setTLSMode(GV, *D);
   }
 
-  // TODO(cir): maybeSetTrivialComdat(*D, *GV);
+  maybeSetTrivialComdat(*D, GV);
 
   // TODO(cir):
   // Emit the initializer function if necessary.
@@ -3009,11 +3009,14 @@ bool CIRGenModule::supportsCOMDAT() const {
   return getTriple().supportsCOMDAT();
 }
 
-void CIRGenModule::maybeSetTrivialComdat(const Decl &D, mlir::Operation *Op) {
-  if (!shouldBeInCOMDAT(*this, D))
+void CIRGenModule::maybeSetTrivialComdat(const Decl &d, mlir::Operation *op) {
+  if (!shouldBeInCOMDAT(*this, d))
     return;
-
-  // TODO: Op.setComdat
+  auto globalOp = dyn_cast_or_null<mlir::cir::GlobalOp>(op);
+  if (globalOp)
+    globalOp.setComdat(true);
+  // Keep it as missing feature as we need to implement comdat for FuncOp.
+  // in the future.
   assert(!MissingFeatures::setComdat() && "NYI");
 }
 

clang/lib/CIR/CodeGen/CIRGenModule.h

@@ -682,7 +682,7 @@ class CIRGenModule : public CIRGenTypeCache {
                                 clang::GlobalDecl &Result) const;
 
   bool supportsCOMDAT() const;
-  void maybeSetTrivialComdat(const clang::Decl &D, mlir::Operation *Op);
+  void maybeSetTrivialComdat(const clang::Decl &d, mlir::Operation *op);
 
   void emitError(const llvm::Twine &message) { theModule.emitError(message); }
 

clang/test/CIR/CodeGen/cxx1z-inline-variables.cpp

@@ -26,18 +26,25 @@ const int &compat_use_after_redecl1 = compat::c;
 const int &compat_use_after_redecl2 = compat::d;
 const int &compat_use_after_redecl3 = compat::g;
 
-// CIR: cir.global  weak_odr @_ZN6compat1bE = #cir.int<2> : !s32i {alignment = 4 : i64}
-// CIR: cir.global  weak_odr @_ZN6compat1aE = #cir.int<1> : !s32i {alignment = 4 : i64}
-// CIR: cir.global  weak_odr @_ZN6compat1cE = #cir.int<3> : !s32i {alignment = 4 : i64}
+// CIR: cir.global  weak_odr comdat @_ZN6compat1bE = #cir.int<2> : !s32i {alignment = 4 : i64}
+// CIR: cir.global  weak_odr comdat @_ZN6compat1aE = #cir.int<1> : !s32i {alignment = 4 : i64}
+// CIR: cir.global  weak_odr comdat @_ZN6compat1cE = #cir.int<3> : !s32i {alignment = 4 : i64}
 // CIR: cir.global  external @_ZN6compat1eE = #cir.int<5> : !s32i {alignment = 4 : i64}
-// CIR: cir.global  weak_odr @_ZN6compat1fE = #cir.int<6> : !s32i {alignment = 4 : i64}
-// CIR: cir.global  linkonce_odr @_ZN6compat1dE = #cir.int<4> : !s32i {alignment = 4 : i64}
-// CIR: cir.global  linkonce_odr @_ZN6compat1gE = #cir.int<7> : !s32i {alignment = 4 : i64}
+// CIR: cir.global  weak_odr comdat @_ZN6compat1fE = #cir.int<6> : !s32i {alignment = 4 : i64}
+// CIR: cir.global  linkonce_odr comdat @_ZN6compat1dE = #cir.int<4> : !s32i {alignment = 4 : i64}
+// CIR: cir.global  linkonce_odr comdat @_ZN6compat1gE = #cir.int<7> : !s32i {alignment = 4 : i64}
 
-// LLVM: @_ZN6compat1bE = weak_odr global i32 2, align 4
-// LLVM: @_ZN6compat1aE = weak_odr global i32 1, align 4
-// LLVM: @_ZN6compat1cE = weak_odr global i32 3, align 4
+// LLVM: $_ZN6compat1bE = comdat any
+// LLVM: $_ZN6compat1aE = comdat any
+// LLVM: $_ZN6compat1cE = comdat any
+// LLVM: $_ZN6compat1fE = comdat any
+// LLVM: $_ZN6compat1dE = comdat any
+// LLVM: $_ZN6compat1gE = comdat any
+
+// LLVM: @_ZN6compat1bE = weak_odr global i32 2, comdat, align 4
+// LLVM: @_ZN6compat1aE = weak_odr global i32 1, comdat, align 4
+// LLVM: @_ZN6compat1cE = weak_odr global i32 3, comdat, align 4
 // LLVM: @_ZN6compat1eE = global i32 5, align 4
-// LLVM: @_ZN6compat1fE = weak_odr global i32 6, align 4
-// LLVM: @_ZN6compat1dE = linkonce_odr global i32 4, align 4
-// LLVM: @_ZN6compat1gE = linkonce_odr global i32 7, align 4
+// LLVM: @_ZN6compat1fE = weak_odr global i32 6, comdat, align 4
+// LLVM: @_ZN6compat1dE = linkonce_odr global i32 4, comdat, align 4
+// LLVM: @_ZN6compat1gE = linkonce_odr global i32 7, comdat, align 4

clang/test/CIR/CodeGen/weak.c

@@ -23,7 +23,7 @@ void active (void)
 // LLVM-NEXT:  call void @B()
 
 int __attribute__((selectany)) y;
-// CIR:      cir.global weak_odr @y
+// CIR:      cir.global weak_odr comdat @y
 
 int __attribute__((weak)) x;
 // CIR:      cir.global weak