Revert "Don't apply nomerge for the first instance of each TrapBB type, per"

This reverts commit 5107ce194c9b03c2f32eb1508df0c92b13b3e2fd.

Doesn't work because CodeGen happens before inlining, so the ubsantraps in functions f(), g() and m() will not have nomerge.

Author: thurstond

clang/lib/CodeGen/CGExpr.cpp

@@ -3915,7 +3915,6 @@ void CodeGenFunction::EmitTrapCheck(llvm::Value *Checked,
                               Builder.getCurrentDebugLocation());
     Builder.CreateCondBr(Checked, Cont, TrapBB);
   } else {
-    bool NewTrapBB = (TrapBB == nullptr);
     TrapBB = createBasicBlock("trap");
     Builder.CreateCondBr(Checked, Cont, TrapBB);
     EmitBlock(TrapBB);
@@ -3929,8 +3928,7 @@ void CodeGenFunction::EmitTrapCheck(llvm::Value *Checked,
                                     CGM.getCodeGenOpts().TrapFuncName);
       TrapCall->addFnAttr(A);
     }
-    if (!NewTrapBB)
-        TrapCall->addFnAttr(llvm::Attribute::NoMerge);
+    TrapCall->addFnAttr(llvm::Attribute::NoMerge);
     TrapCall->setDoesNotReturn();
     TrapCall->setDoesNotThrow();
     Builder.CreateUnreachable();

clang/test/CodeGen/ubsan-trap-merge.c

@@ -55,7 +55,7 @@ int g(int x) {
 // CHECK-NEXT:    [[TMP3:%.*]] = extractvalue { i32, i1 } [[TMP2]], 1, !nosanitize [[META2]]
 // CHECK-NEXT:    br i1 [[TMP3]], label %[[TRAP1:.*]], label %[[CONT2:.*]], !nosanitize [[META2]]
 // CHECK:       [[TRAP1]]:
-// CHECK-NEXT:    tail call void @llvm.ubsantrap(i8 0) #[[ATTR5:[0-9]+]], !nosanitize [[META2]]
+// CHECK-NEXT:    tail call void @llvm.ubsantrap(i8 0) #[[ATTR4]], !nosanitize [[META2]]
 // CHECK-NEXT:    unreachable, !nosanitize [[META2]]
 // CHECK:       [[CONT2]]:
 // CHECK-NEXT:    [[TMP4:%.*]] = extractvalue { i32, i1 } [[TMP2]], 0, !nosanitize [[META2]]
@@ -102,5 +102,4 @@ int m(int x, int y) {
   return f(x) + g(y);
 }
 //.
-// CHECK: attributes #[[ATTR4]] = { noreturn nounwind }
-// CHECK: attributes #[[ATTR5]] = { nomerge noreturn nounwind }
+// CHECK: attributes #[[ATTR4]] = { nomerge noreturn nounwind }