[MC,COFF] .safeseh: avoid changeSection (#132624)

The directive temporarily switches to the .sxdata section to emit data,
and then calls `insert`, which makes `CurFrag` out of sync of the
current section. Call push/switch/pop instead.

Related to #132464

(cherry picked from commit ece72e2)

Author: MaskRay

llvm/lib/MC/MCWinCOFFStreamer.cpp

@@ -299,7 +299,8 @@ void MCWinCOFFStreamer::emitCOFFSafeSEH(MCSymbol const *Symbol) {
     return;
 
   MCSection *SXData = getContext().getObjectFileInfo()->getSXDataSection();
-  changeSection(SXData);
+  pushSection();
+  switchSection(SXData);
   SXData->ensureMinAlignment(Align(4));
 
   insert(getContext().allocFragment<MCSymbolIdFragment>(Symbol));
@@ -310,6 +311,7 @@ void MCWinCOFFStreamer::emitCOFFSafeSEH(MCSymbol const *Symbol) {
   // function. Go ahead and oblige it here.
   CSymbol->setType(COFF::IMAGE_SYM_DTYPE_FUNCTION
                    << COFF::SCT_COMPLEX_TYPE_SHIFT);
+  popSection();
 }
 
 void MCWinCOFFStreamer::emitCOFFSymbolIndex(MCSymbol const *Symbol) {

llvm/test/CodeGen/X86/win32-eh.ll

@@ -1,4 +1,5 @@
 ; RUN: llc -mtriple=i686-pc-windows-msvc < %s | FileCheck %s
+; RUN: llc -mtriple=i686-pc-windows-msvc -filetype=obj < %s -o %t
 
 declare void @may_throw_or_crash()
 declare i32 @_except_handler3(...)
@@ -208,6 +209,14 @@ catch:
 ; CHECK-NEXT:  .long   0
 ; CHECK-NEXT:  .long   1
 
+; CHECK-LABEL: inlineasm:
+; CHECK: .safeseh my_handler
+define i32 @inlineasm() {
+entry:
+  call void asm sideeffect ".safeseh my_handler", "~{dirflag},~{fpsr},~{flags}"()
+  ret i32 0
+}
+
 ; CHECK-LABEL: ___ehhandler$use_CxxFrameHandler3:
 ; CHECK: movl $L__ehtable$use_CxxFrameHandler3, %eax
 ; CHECK-NEXT: jmp  ___CxxFrameHandler3 # TAILCALL