[GlobalIsel] Fix fallback if stack protector isn't supported.

[efriedma]

Summary

When GlobalISel fails, we need to report the error, and we need to set the FailedISel property. We skipped those steps if stack protector insertion failed, which led to a very strange miscompile.

[paquette]

LGTM, thanks!

llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp

#endif // ifndef NDEBUG
 
           R << ": '" << InstStr.str() << "'";
         }
 
         reportTranslationError(*MF, *TPC, *ORE, R);
         return false;
       }
 
-      if (!finalizeBasicBlock(*BB, MBB))
+      if (!finalizeBasicBlock(*BB, MBB)) {
+        OptimizationRemarkMissed R("gisel-irtranslator", "GISelFailure",
+                                   BB->getTerminator()->getDebugLoc(), BB);
+        R << "unable to translate basic block";
+        reportTranslationError(*MF, *TPC, *ORE, R);
         return false;
       }
+    }
 #ifndef NDEBUG
     WrapperObserver.removeObserver(&Verifier);
 #endif
   }
 
   finishPendingPhis();
 
   SwiftError.propagateVRegs();

llvm/test/CodeGen/AArch64/GlobalISel/irtranslator-stack-protector-windows.ll

+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -verify-machineinstrs -mtriple=aarch64-pc-windows-msvc %s -o - -global-isel -global-isel-abort=0 | FileCheck %s
+
+; Make sure we correctly fall back to SelectionDAG isel for unsupported stack protectors.
+
+define void @caller() sspreq {
+; CHECK-LABEL: caller:
+; CHECK:       .seh_proc caller
+; CHECK-NEXT:  // %bb.0: // %entry
+; CHECK-NEXT:    sub sp, sp, #32
+; CHECK-NEXT:    .seh_stackalloc 32
+; CHECK-NEXT:    str x30, [sp, #16] // 8-byte Folded Spill
+; CHECK-NEXT:    .seh_save_reg x30, 16
+; CHECK-NEXT:    .seh_endprologue
+; CHECK-NEXT:    adrp x8, __security_cookie
+; CHECK-NEXT:    add x0, sp, #4
+; CHECK-NEXT:    ldr x8, [x8, :lo12:__security_cookie]
+; CHECK-NEXT:    str x8, [sp, #8]
+; CHECK-NEXT:    bl callee
+; CHECK-NEXT:    ldr x0, [sp, #8]
+; CHECK-NEXT:    bl __security_check_cookie
+; CHECK-NEXT:    .seh_startepilogue
+; CHECK-NEXT:    ldr x30, [sp, #16] // 8-byte Folded Reload
+; CHECK-NEXT:    .seh_save_reg x30, 16
+; CHECK-NEXT:    add sp, sp, #32
+; CHECK-NEXT:    .seh_stackalloc 32
+; CHECK-NEXT:    .seh_endepilogue
+; CHECK-NEXT:    ret
+; CHECK-NEXT:    .seh_endfunclet
+; CHECK-NEXT:    .seh_endproc
+entry:
+  %x = alloca i32, align 4
+  %0 = bitcast i32* %x to i8*
+  call void @callee(i32* nonnull %x)
+  ret void
+}
+
+declare void @callee(i32*)